Marspedia - User contributions [en]

Water

2021-09-05T17:51:42Z

JimL: Added 1 more citation.

[[Image:GlassOfWater.jpg|thumb|200px|right|A glass is filled with drinking water.]]

'''Water''' is a chemical compound consisting of a single [[oxygen]] atom bonded to two [[hydrogen]] atoms (''chemical symbols:'' H2O). Water is essential to all known forms of life, and its unique properties make it invaluable for most industrial processes. While water in the liquid phase is abundant on [[Earth]], its icy deposits on [[Mars]] make it into a critical resource to be treasured.

==Evidence for water on Mars==

[[Image:388886main_mars_ice_226x170.jpg|thumb|226px|right|A new crater full of melting ice, as seen from the Mars Reconnaissance Orbiter.]]

[[File:PIA15090nirgalvallismariner9.jpg|thumb|226px|left|Nirgal Vallis, as seen by Mariner 9 This is one of the first images to show evidence of past water on Mars.]]

Starting in 2004, the evidence of the presence of water on Mars has been mounting.

===Past liquid water===
Mars shows evidence of extensive liquid water flowing on its surface in the past and it is the focus of many Mars missions to find out how this water has leaked away over the millennia.

The 1996 [[Mars Pathfinder]] mission discovered plentiful evidence that its landing site, [[Ares Vallis]], was once the bottom of a huge valley system eroded by ancient water.

In 2004, the [[Opportunity]] rover discovered geological markers - stratification and cross-bedding - near its landing site which pointed to significant flows of water at some time in Mars' history.<ref>Michael P. Lamb, John P. Grotzinger, John B. Southard, Nicholas J. Tosca, 2012. "Were Aqueous Ripples on Mars Formed by Flowing Brines?", Sedimentary Geology of Mars, John P. Grotzinger, Ralph E. Milliken. <nowiki>https://doi.org/10.2110/pec.12.102.0139</nowiki></ref>

The Mars Express Orbiter used [[Imaging Spectroscopy|imaging spectroscopy]] to detect hydrated minerals in 2005, strong evidence that surface water was once present in large amounts and for a long duration.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #1. Hydrated minerals – evidence of liquid water on Mars. <nowiki>https://sci.esa.int/web/mars-express/-/51821-1-hydrated-minerals-ndash-evidence-of-liquid-water-on-mars</nowiki></ref>

Further support for the historic existence of flowing water comes from the first observations made by NASA's [[Mars Reconnaissance Orbiter]] (launched in 2005) where the High Resolution Imaging Science Experiment (HiRISE) camera spotted small fractures and cracks in the Martian canyon, [[Candor Chasma]]. The cracks analyzed show signs of mineral alteration in the rock exposed - a sign that liquid water once flowed through these sub-surface pipes.

:"''What caught my eye was the bleaching or lack of dark material along the fracture. That is a sign of mineral alteration by fluids that moved through those joints. It reminded me of something I had seen during field studies in Utah, that is light-tone zones, or 'haloes,' on either side of cracks through darker sandstone''" - Dr. Chris Okubo, a geologist at the University of Arizona, Tucson.

Although this is a sign that the liquid water has since disappeared from these cracks and fractures in the canyon rock, it is interesting to find evidence for ancient water in abundance.

===Current water ice===
Today, water on Mars appears to be concentrated in Martian polar ice, suggesting Mars may once have had a warmer climate, slowly cooling as the atmosphere became a more inefficient insulator for the meager heating from the distant Sun.

In 2004 the [[Mars Express]] orbiter detected spectral evidence of water in the south pole's ice cap and the surrounding area, which ruled out the possibility that the southern ice cap consisted of only carbon dioxide ice.<ref>European Space Agency. March 17, 2004. Water at Martian south pole. https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Water_at_Martian_south_pole</ref>

In 2005, [[Mars Express]] located an area of solid water ice near the north pole.

The Phoenix lander confirmed in 2008 that water ice is not limited to the extreme polar regions.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref>

Photos from the [[Mars Reconnaissance Orbiter]] show frozen water just below the Martian surface (see photograph). Surprisingly the location is far away from the poles (43.28 degrees north latitude, 164.22 degrees east longitude), which raises the hope of large amounts of water all over the planet.
<ref>[http://www.nasa.gov/mission_pages/MRO/news/mro20090924.html Mars Reconnaissance Orbiter Sees Ice Exposed by Meteor Impact]</ref>

====Abundance====
[[Image:MARSIS.jpg|thumb|200px|right|A MARSIS map of Mars' south pole ice deposits.]]
On March 15, 2007, [[Mars Express]]' mission control released more news of extensive frozen water discovered at the Martian [[south pole]]. These new and highly accurate measurements predict that if the ice were to be melted, the whole planet would be covered in a liquid layer 11 meters deep.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #4. Probing the polar regions. <nowiki>https://sci.esa.int/web/mars-express/-/51824-4-probing-the-polar-regions</nowiki></ref> Although it has been known for many years that the poles have an abundance of ice, it has never been measured to this degree of accuracy. The data comes from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) currently mapping the north pole to gain a better understanding of how much frozen water may be contained there. MARSIS can probe over 2 miles below the Martian surface and has found extensive layered deposits of ice.

===Current liquid water===

Future manned exploration on Mars will require a source of water whether it is in the form of ice or sub-surface [[aquifers]]. The [[Mars Express]] orbiter has uncovered some confusing measurements suggesting there may be liquid water accompanying all that ice. MARSIS bounced back data suggesting at least 90% of the layered deposits under the polar cap are indeed supplies of ice, but a thin layer resembling liquid water is also evident. It is hard to understand the existence of liquid water at the extremely low temperatures predicted. Perhaps high pressures or small geological processes may explain these observations. Another orbiter, NASA's Mars Global Surveyor, has also returned some exciting new evidence for the existence of new flows of liquid water on the Martian surface away from the frozen poles. {{science question|What pressures are required to keep water in a liquid phase at temperatures as low as that on the surface of Mars? - [[User:Ioneill|Ioneill]]}}

The [[Mars Global Surveyor]] arrived at the Red Planet on September 11, 1997 and returned a decade of data on the evolution of the planet before it was lost in November 2006 through energy loss. It was Mars' longest operational artificial satellite. The Mars Orbiter Camera (MOC) onboard revealed new deposits possibly carried as sediment by flowing water in two locations in the past 7 years (press release dated December 6, 2006)<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref>. In images taken in August 1999 and September 2006 of the same location ([[Centauri Montes]] Region), a bright deposit measuring several hundred meters long is evident in the 2006 image but not in the 1999 image. A similar feature was observed at a different location from 2001 to 2005 at [[Terra Sirenum]]. It is worth noting that both locations are in equatorial regions, not usually associated with ice or liquid water. This suggests liquid water remains a characteristic of the Mars landscape, if only sporadically. These discoveries have increased the enthusiasm for the search for [[microbes|microbial life]], but the implications for manned exploration are huge. If there are pockets of liquid water just below the surface, Mars may yet be able to provide our future pioneers with natural springs more familiar on Earth.
[[Image:Water_deposit.jpg|thumb|left|200px|Evidence from the [[Mars Global Surveyor]] MOC instrument that spurts of liquid water may sporadically flow on the Martian surface]]
However, surface water on Mars is short-lived. The Martian atmosphere is very thin (a pressure of 7 millibars, <1% that of Earth's thick atmosphere) and cold (an average global temperature of -55°C or -67F), these two factors deny any long-term existence of liquid water. Surface liquid water will quickly freeze and [[sublimation|sublime]] into the atmosphere, bypassing the [[triple point|liquid phase]]. This phase transition for water on Mars is much like the phase transition for liquid carbon dioxide on Earth when it is released from a CO2 fire extinguisher to produce dry ice snow and CO2 gas. The phase transition for H2O on the surface of Mars occurs below the "[[triple point]]" on the phase diagram so the recent observations of sediment on the surface will have been deposited very quickly by short lived "spurts" of water. Just how short-lived these spurts of water are it is unknown, but a significant volume must have created a formidable river to carry sediment several hundred meters.

At times, the humidity of the Martian atmosphere can reach 100% (at Mars' temperature and pressure). If the temperature was high, salty brines could last several minutes on the Martian surface.

Although there may be other explanations for these long "channels" of sediment, such as rock slides or wind-blown [[sand]] features, the appearance of the deposits seem very water-like. Michael Malin of Malin Space Science Systems, a mission scientist for the MOC says, "''The shapes of these deposits are what you would expect to see if the material were carried by flowing water... they have finger-like branches at the downhill end and easily diverted around small obstacles''".<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref> It is also possible that other liquids such as 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 1,3-propanediol, ethylene glycol and related liquids could be responsible for [[Recent Liquid Flow on Mars|fluid flow features]] on Mars. While such liquids would be relatively more rare than water, the resistance to freezing of such liquids and mixtures of such liquids with water would allow them to cause fluid flow effects where pure liquid water is impossible.

==Water production==
Water production on Mars for settlement use or for exploration uses can take many forms. As a prime [[In-situ resource utilization|In-situ]] resource the presence of water on Mars is one of its main attractions. Further exploration is needed to determine if the water is available in a relatively pure form, or if it will contain salts and other chemical contaminants requiring water treatment.

===Atmosphere===
The Martian [[atmosphere]] contains water vapour (which on occasion can reach 100% humidity). However, it is normally dry and very thin, which makes extracting water slow and energy intensive. With a device similar to an [[atmospheric mining|air dehumidifier]] the production of water should be feasible all over the planet's surface. An [[experimental setup#water out of the atmosphere|experimental setup]] is necessary to find out all about the viability of this approach.

===Caves===
Since the discovery of [[caves]] scientists believe in the possibility of water ice on the ground of the caves. Water ice is abundant under the ground at least near the poles, and probably elsewhere too.

===Glaciers===
The [[Mars Reconnaissance Orbiter]] has found evidence of [[glacier|glaciers]] covered in regolith.<ref>http://www.nasa.gov/home/hqnews/2008/nov/HQ_08-304_MRO_BuriedGlaciers.html</ref> Radar reflection data indicates that these are not Rock Glaciers that have been previously suspected on Mars, but instead are thick glacial ice covered in a thin layer of debris. The buried glaciers lie in the [[Hellas Planitia|Hellas Basin]] region of Mars' southern hemisphere with similar aprons detected extending from cliffs in the northern hemisphere.

===Regolith===
Water is present in the martian regolith both as ice and as hydrated minerals. In addition, a recent paper has shown that a huge amount of water has been absorbed by rocks. On Earth, plate Tectonics takes these hydrated minerals and melts them, where water can return to the surface via vulcanism. On Mars the water remains in these minerals. <ref>https://science.sciencemag.org/content/early/2021/03/15/science.abc7717 - Long term drying of Mars by sequestration of Ocean-scale volumes of water in the crust</ref>

===Polar regions===
The martian polar regions have extensive ice caps as well as ice filled craters, such as the [[Korolev]] crater, that could serve as water sources. As the poles are usually extremely cold, sources closer to the equator would be more useful for future martian settlements. Note that permafrost has been detected at all latitudes, but above 30 degrees latitude, surface ice is found fairly often.

==Uses==

===Drinking water===
The [[human]] metabolism requires a regular intake of fresh water. Pure liquid water is non-existent on Mars but there is abundant frozen water and hydrated minerals. Since getting liquid water for use will require some industrial effort, the [[recycling]] of all excretion would provide advantages in reducing water use. There are two ways: Wastewater can be [[Potable_water_treatment|treated]], which is partially done on the [[ISS]] already. Alternatively, the water can be kept in a nearly natural cycle, using parts of the [[greenhouse]]s for [[biological wastewater treatment]].

The concentration of deuterium in Martian hydrogen and thus in Martian water is between five and thirteen ten-thousandth-parts.<ref>[http://www.sciencemag.org/content/240/4860/1767.abstract abstract in ''Science'']</ref> or about six times the relative abundance on Earth. Still this concentration is far from the 25% of the body's content of hydrogen that would need to be substituted by deuterium before there are any serious health effects. Deuterium is not a cumulative poison. At about one thousandth part of the hydrogen in Martian water, deuterium would be excreted as fast as it is consumed and would not be a health problem.

===Industrial processes===

Many industrial processes considered for a Mars settlement, in particular the production of [[methanol]] and [[methane]] and other hydrocarbons require hydrogen. This can be obtained by [[electrolysis]] or via thermolysis such as the Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2006.05.013</ref> or the Zinc/Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2015.11.049</ref>. In electrolysis or basic thermolysis, [[Oxygen O2]] is produced as a byproduct. In the Zinc/Sulfur/Iodine cycle, CO2 and H2O are inputs and the outputs are CO and H2. CO is industrially useful in the production of [[methanol]] and other [[Hydrocarbon_synthesis|hydrocarbons]], as well as in mineral refining via the [https://en.wikipedia.org/wiki/Mond_process Mond process]. The H2 can also be combined with atmospheric N2 using a [https://en.wikipedia.org/wiki/Haber_process Haber reactor] to produce [[ammonia]].

Most other processes require the use of significant quantities of water as a [[solvent]] for reagents such as [[acid]]s or [[ammonia]] or a a coolant for high temperature systems.

Power sources which rely on heat engines (such as [[nuclear power]]) require a heat sink to provide the heat differential required for the engine to run. Water or Ice make good materials for this heat sink as they are dense and have high thermal mass. The ice of [[korolev|Korolev Crater]] has been suggested as a potential heat sink sufficient to provide for colony scale power generation.

[[Deuterium]] from martian water may provide a source of fusion fuel for future energy production. Note that deuterium is 2.5 times more concentrated on Mars than on Earth, and may form a viable export.

[[Methanol]] and [[methane]] may be used to feed [[Biological_reactors|methanotrophs]] to produce food or other biologically produced industrial materials.

==See Also==

*[[Martian features that are signs of water ice]]
*[[Sublimation]]
*[[Water Infrastructure|Water infrastructure]] and waste water treatment
*"Mars: A Warmer Wetter Planet", by Jeffrey S. Kargel, ISBN 1-85233-568-8. This important book collected the evidence of water on Mars, and put to rest the idea that Mars had always been a dry planet.

==External links==

*[https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

*[http://en.wikipedia.org/wiki/Water Wikipedia page on water]
*[http://mars.jpl.nasa.gov/express/mission/sc_science_marsis02.html Searching for water with the Mars Express MARSIS instrument.]
*[https://en.wikipedia.org/wiki/Water_on_Mars Wikipedia page on water on Mars]

*[https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]
*[https://www.youtube.com/watch?v=QWcdAvFN_q0 James Wray - The Search for Water and Life on Mars (and Beyond) (November 15, 2018)]
*[https://www.youtube.com/watch?v=b4hCWIQsyps Mars: Ancient Water, Present Day Ice]
*[https://www.youtube.com/watch?v=EJk0hS4_gz4 Water on Mars and the Potential for Martian Life]
*[https://www.youtube.com/watch?v=GX9XzRyuYLc Oceans and Life on Mars]

===References===
<references />

Water

2021-09-05T17:47:18Z

JimL: Tried to improve on the organization, details, and citations of the 'Current water ice' section.

[[Image:GlassOfWater.jpg|thumb|200px|right|A glass is filled with drinking water.]]

'''Water''' is a chemical compound consisting of a single [[oxygen]] atom bonded to two [[hydrogen]] atoms (''chemical symbols:'' H2O). Water is essential to all known forms of life, and its unique properties make it invaluable for most industrial processes. While water in the liquid phase is abundant on [[Earth]], its icy deposits on [[Mars]] make it into a critical resource to be treasured.

==Evidence for water on Mars==

[[Image:388886main_mars_ice_226x170.jpg|thumb|226px|right|A new crater full of melting ice, as seen from the Mars Reconnaissance Orbiter.]]

[[File:PIA15090nirgalvallismariner9.jpg|thumb|226px|left|Nirgal Vallis, as seen by Mariner 9 This is one of the first images to show evidence of past water on Mars.]]

Starting in 2004, the evidence of the presence of water on Mars has been mounting.

===Past liquid water===
Mars shows evidence of extensive liquid water flowing on its surface in the past and it is the focus of many Mars missions to find out how this water has leaked away over the millennia.

The 1996 [[Mars Pathfinder]] mission discovered plentiful evidence that its landing site, [[Ares Vallis]], was once the bottom of a huge valley system eroded by ancient water.

In 2004, the [[Opportunity]] rover discovered geological markers - stratification and cross-bedding - near its landing site which pointed to significant flows of water at some time in Mars' history.<ref>Michael P. Lamb, John P. Grotzinger, John B. Southard, Nicholas J. Tosca, 2012. "Were Aqueous Ripples on Mars Formed by Flowing Brines?", Sedimentary Geology of Mars, John P. Grotzinger, Ralph E. Milliken. <nowiki>https://doi.org/10.2110/pec.12.102.0139</nowiki></ref>

The Mars Express Orbiter used [[Imaging Spectroscopy|imaging spectroscopy]] to detect hydrated minerals in 2005, strong evidence that surface water was once present in large amounts and for a long duration.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #1. Hydrated minerals – evidence of liquid water on Mars. <nowiki>https://sci.esa.int/web/mars-express/-/51821-1-hydrated-minerals-ndash-evidence-of-liquid-water-on-mars</nowiki></ref>

Further support for the historic existence of flowing water comes from the first observations made by NASA's [[Mars Reconnaissance Orbiter]] (launched in 2005) where the High Resolution Imaging Science Experiment (HiRISE) camera spotted small fractures and cracks in the Martian canyon, [[Candor Chasma]]. The cracks analyzed show signs of mineral alteration in the rock exposed - a sign that liquid water once flowed through these sub-surface pipes.

:"''What caught my eye was the bleaching or lack of dark material along the fracture. That is a sign of mineral alteration by fluids that moved through those joints. It reminded me of something I had seen during field studies in Utah, that is light-tone zones, or 'haloes,' on either side of cracks through darker sandstone''" - Dr. Chris Okubo, a geologist at the University of Arizona, Tucson.

Although this is a sign that the liquid water has since disappeared from these cracks and fractures in the canyon rock, it is interesting to find evidence for ancient water in abundance.

===Current water ice===
Today, water on Mars appears to be concentrated in Martian polar ice, suggesting Mars may once have had a warmer climate, slowly cooling as the atmosphere became a more inefficient insulator for the meager heating from the distant Sun.

In 2004 the [[Mars Express]] orbiter detected spectral evidence of water in the south pole's ice cap and the surrounding area, which ruled out the possibility that the southern ice cap consisted of only carbon dioxide ice.<ref>European Space Agency. March 17, 2004. Water at Martian south pole. https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Water_at_Martian_south_pole</ref>

In 2005, [[Mars Express]] located an area of solid water ice near the north pole.

The Phoenix lander confirmed in 2008 that water ice is not limited to the extreme polar regions.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref>

Photos from the [[Mars Reconnaissance Orbiter]] show frozen water just below the Martian surface (see photograph). Surprisingly the location is far away from the poles (43.28 degrees north latitude, 164.22 degrees east longitude), which raises the hope of large amounts of water all over the planet.
<ref>[http://www.nasa.gov/mission_pages/MRO/news/mro20090924.html Mars Reconnaissance Orbiter Sees Ice Exposed by Meteor Impact]</ref>

====Abundance====
[[Image:MARSIS.jpg|thumb|200px|right|A MARSIS map of Mars' south pole ice deposits.]]
On March 15, 2007, [[Mars Express]]' mission control released more news of extensive frozen water discovered at the Martian [[south pole]]. These new and highly accurate measurements predict that if the ice were to be melted, the whole planet would be covered in a liquid layer 11 meters deep. Although it has been known for many years that the poles have an abundance of ice, it has never been measured to this degree of accuracy. The data comes from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) currently mapping the north pole to gain a better understanding of how much frozen water may be contained there. MARSIS can probe over 2 miles below the Martian surface and has found extensive layered deposits of ice.

===Current liquid water===

Future manned exploration on Mars will require a source of water whether it is in the form of ice or sub-surface [[aquifers]]. The [[Mars Express]] orbiter has uncovered some confusing measurements suggesting there may be liquid water accompanying all that ice. MARSIS bounced back data suggesting at least 90% of the layered deposits under the polar cap are indeed supplies of ice, but a thin layer resembling liquid water is also evident. It is hard to understand the existence of liquid water at the extremely low temperatures predicted. Perhaps high pressures or small geological processes may explain these observations. Another orbiter, NASA's Mars Global Surveyor, has also returned some exciting new evidence for the existence of new flows of liquid water on the Martian surface away from the frozen poles. {{science question|What pressures are required to keep water in a liquid phase at temperatures as low as that on the surface of Mars? - [[User:Ioneill|Ioneill]]}}

The [[Mars Global Surveyor]] arrived at the Red Planet on September 11, 1997 and returned a decade of data on the evolution of the planet before it was lost in November 2006 through energy loss. It was Mars' longest operational artificial satellite. The Mars Orbiter Camera (MOC) onboard revealed new deposits possibly carried as sediment by flowing water in two locations in the past 7 years (press release dated December 6, 2006)<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref>. In images taken in August 1999 and September 2006 of the same location ([[Centauri Montes]] Region), a bright deposit measuring several hundred meters long is evident in the 2006 image but not in the 1999 image. A similar feature was observed at a different location from 2001 to 2005 at [[Terra Sirenum]]. It is worth noting that both locations are in equatorial regions, not usually associated with ice or liquid water. This suggests liquid water remains a characteristic of the Mars landscape, if only sporadically. These discoveries have increased the enthusiasm for the search for [[microbes|microbial life]], but the implications for manned exploration are huge. If there are pockets of liquid water just below the surface, Mars may yet be able to provide our future pioneers with natural springs more familiar on Earth.
[[Image:Water_deposit.jpg|thumb|left|200px|Evidence from the [[Mars Global Surveyor]] MOC instrument that spurts of liquid water may sporadically flow on the Martian surface]]
However, surface water on Mars is short-lived. The Martian atmosphere is very thin (a pressure of 7 millibars, <1% that of Earth's thick atmosphere) and cold (an average global temperature of -55°C or -67F), these two factors deny any long-term existence of liquid water. Surface liquid water will quickly freeze and [[sublimation|sublime]] into the atmosphere, bypassing the [[triple point|liquid phase]]. This phase transition for water on Mars is much like the phase transition for liquid carbon dioxide on Earth when it is released from a CO2 fire extinguisher to produce dry ice snow and CO2 gas. The phase transition for H2O on the surface of Mars occurs below the "[[triple point]]" on the phase diagram so the recent observations of sediment on the surface will have been deposited very quickly by short lived "spurts" of water. Just how short-lived these spurts of water are it is unknown, but a significant volume must have created a formidable river to carry sediment several hundred meters.

At times, the humidity of the Martian atmosphere can reach 100% (at Mars' temperature and pressure). If the temperature was high, salty brines could last several minutes on the Martian surface.

Although there may be other explanations for these long "channels" of sediment, such as rock slides or wind-blown [[sand]] features, the appearance of the deposits seem very water-like. Michael Malin of Malin Space Science Systems, a mission scientist for the MOC says, "''The shapes of these deposits are what you would expect to see if the material were carried by flowing water... they have finger-like branches at the downhill end and easily diverted around small obstacles''".<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref> It is also possible that other liquids such as 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 1,3-propanediol, ethylene glycol and related liquids could be responsible for [[Recent Liquid Flow on Mars|fluid flow features]] on Mars. While such liquids would be relatively more rare than water, the resistance to freezing of such liquids and mixtures of such liquids with water would allow them to cause fluid flow effects where pure liquid water is impossible.

==Water production==
Water production on Mars for settlement use or for exploration uses can take many forms. As a prime [[In-situ resource utilization|In-situ]] resource the presence of water on Mars is one of its main attractions. Further exploration is needed to determine if the water is available in a relatively pure form, or if it will contain salts and other chemical contaminants requiring water treatment.

===Atmosphere===
The Martian [[atmosphere]] contains water vapour (which on occasion can reach 100% humidity). However, it is normally dry and very thin, which makes extracting water slow and energy intensive. With a device similar to an [[atmospheric mining|air dehumidifier]] the production of water should be feasible all over the planet's surface. An [[experimental setup#water out of the atmosphere|experimental setup]] is necessary to find out all about the viability of this approach.

===Caves===
Since the discovery of [[caves]] scientists believe in the possibility of water ice on the ground of the caves. Water ice is abundant under the ground at least near the poles, and probably elsewhere too.

===Glaciers===
The [[Mars Reconnaissance Orbiter]] has found evidence of [[glacier|glaciers]] covered in regolith.<ref>http://www.nasa.gov/home/hqnews/2008/nov/HQ_08-304_MRO_BuriedGlaciers.html</ref> Radar reflection data indicates that these are not Rock Glaciers that have been previously suspected on Mars, but instead are thick glacial ice covered in a thin layer of debris. The buried glaciers lie in the [[Hellas Planitia|Hellas Basin]] region of Mars' southern hemisphere with similar aprons detected extending from cliffs in the northern hemisphere.

===Regolith===
Water is present in the martian regolith both as ice and as hydrated minerals. In addition, a recent paper has shown that a huge amount of water has been absorbed by rocks. On Earth, plate Tectonics takes these hydrated minerals and melts them, where water can return to the surface via vulcanism. On Mars the water remains in these minerals. <ref>https://science.sciencemag.org/content/early/2021/03/15/science.abc7717 - Long term drying of Mars by sequestration of Ocean-scale volumes of water in the crust</ref>

===Polar regions===
The martian polar regions have extensive ice caps as well as ice filled craters, such as the [[Korolev]] crater, that could serve as water sources. As the poles are usually extremely cold, sources closer to the equator would be more useful for future martian settlements. Note that permafrost has been detected at all latitudes, but above 30 degrees latitude, surface ice is found fairly often.

==Uses==

===Drinking water===
The [[human]] metabolism requires a regular intake of fresh water. Pure liquid water is non-existent on Mars but there is abundant frozen water and hydrated minerals. Since getting liquid water for use will require some industrial effort, the [[recycling]] of all excretion would provide advantages in reducing water use. There are two ways: Wastewater can be [[Potable_water_treatment|treated]], which is partially done on the [[ISS]] already. Alternatively, the water can be kept in a nearly natural cycle, using parts of the [[greenhouse]]s for [[biological wastewater treatment]].

The concentration of deuterium in Martian hydrogen and thus in Martian water is between five and thirteen ten-thousandth-parts.<ref>[http://www.sciencemag.org/content/240/4860/1767.abstract abstract in ''Science'']</ref> or about six times the relative abundance on Earth. Still this concentration is far from the 25% of the body's content of hydrogen that would need to be substituted by deuterium before there are any serious health effects. Deuterium is not a cumulative poison. At about one thousandth part of the hydrogen in Martian water, deuterium would be excreted as fast as it is consumed and would not be a health problem.

===Industrial processes===

Many industrial processes considered for a Mars settlement, in particular the production of [[methanol]] and [[methane]] and other hydrocarbons require hydrogen. This can be obtained by [[electrolysis]] or via thermolysis such as the Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2006.05.013</ref> or the Zinc/Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2015.11.049</ref>. In electrolysis or basic thermolysis, [[Oxygen O2]] is produced as a byproduct. In the Zinc/Sulfur/Iodine cycle, CO2 and H2O are inputs and the outputs are CO and H2. CO is industrially useful in the production of [[methanol]] and other [[Hydrocarbon_synthesis|hydrocarbons]], as well as in mineral refining via the [https://en.wikipedia.org/wiki/Mond_process Mond process]. The H2 can also be combined with atmospheric N2 using a [https://en.wikipedia.org/wiki/Haber_process Haber reactor] to produce [[ammonia]].

Most other processes require the use of significant quantities of water as a [[solvent]] for reagents such as [[acid]]s or [[ammonia]] or a a coolant for high temperature systems.

Power sources which rely on heat engines (such as [[nuclear power]]) require a heat sink to provide the heat differential required for the engine to run. Water or Ice make good materials for this heat sink as they are dense and have high thermal mass. The ice of [[korolev|Korolev Crater]] has been suggested as a potential heat sink sufficient to provide for colony scale power generation.

[[Deuterium]] from martian water may provide a source of fusion fuel for future energy production. Note that deuterium is 2.5 times more concentrated on Mars than on Earth, and may form a viable export.

[[Methanol]] and [[methane]] may be used to feed [[Biological_reactors|methanotrophs]] to produce food or other biologically produced industrial materials.

==See Also==

*[[Martian features that are signs of water ice]]
*[[Sublimation]]
*[[Water Infrastructure|Water infrastructure]] and waste water treatment
*"Mars: A Warmer Wetter Planet", by Jeffrey S. Kargel, ISBN 1-85233-568-8. This important book collected the evidence of water on Mars, and put to rest the idea that Mars had always been a dry planet.

==External links==

*[https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

*[http://en.wikipedia.org/wiki/Water Wikipedia page on water]
*[http://mars.jpl.nasa.gov/express/mission/sc_science_marsis02.html Searching for water with the Mars Express MARSIS instrument.]
*[https://en.wikipedia.org/wiki/Water_on_Mars Wikipedia page on water on Mars]

*[https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]
*[https://www.youtube.com/watch?v=QWcdAvFN_q0 James Wray - The Search for Water and Life on Mars (and Beyond) (November 15, 2018)]
*[https://www.youtube.com/watch?v=b4hCWIQsyps Mars: Ancient Water, Present Day Ice]
*[https://www.youtube.com/watch?v=EJk0hS4_gz4 Water on Mars and the Potential for Martian Life]
*[https://www.youtube.com/watch?v=GX9XzRyuYLc Oceans and Life on Mars]

===References===
<references />

Water

2021-08-01T13:22:48Z

JimL: /* Evidence for water on Mars */ Put all evidence of past liquid water together under one subheading, and added a little more information.

[[Image:GlassOfWater.jpg|thumb|200px|right|A glass is filled with drinking water.]]

'''Water''' is a chemical compound consisting of a single [[oxygen]] atom bonded to two [[hydrogen]] atoms (''chemical symbols:'' H2O). Water is essential to all known forms of life, and its unique properties make it invaluable for most industrial processes. While water in the liquid phase is abundant on [[Earth]], its icy deposits on [[Mars]] make it into a critical resource to be treasured.

==Evidence for water on Mars==

[[Image:388886main_mars_ice_226x170.jpg|thumb|226px|right|A new crater full of melting ice, as seen from the Mars Reconnaissance Orbiter.]]

[[File:PIA15090nirgalvallismariner9.jpg|thumb|226px|left|Nirgal Vallis, as seen by Mariner 9 This is one of the first images to show evidence of past water on Mars.]]

Starting in 2004, the evidence of the presence of water on Mars has been mounting.

=== Past liquid water ===
The 1996 [[Mars Pathfinder]] mission discovered plentiful evidence that its landing site, [[Ares Vallis]], was once the bottom of a huge valley system eroded by ancient water.

In 2004, the [[Opportunity]] rover discovered geological markers - stratification and cross-bedding - near its landing site which pointed to significant flows of water at some time in Mars' history.<ref>Michael P. Lamb, John P. Grotzinger, John B. Southard, Nicholas J. Tosca, 2012. "Were Aqueous Ripples on Mars Formed by Flowing Brines?", Sedimentary Geology of Mars, John P. Grotzinger, Ralph E. Milliken. <nowiki>https://doi.org/10.2110/pec.12.102.0139</nowiki></ref>

The Mars Express Orbiter used [[Imaging Spectroscopy|imaging spectroscopy]] to detect hydrated minerals in 2005, strong evidence that surface water was once present in large amounts and for a long duration.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #1. Hydrated minerals – evidence of liquid water on Mars. <nowiki>https://sci.esa.int/web/mars-express/-/51821-1-hydrated-minerals-ndash-evidence-of-liquid-water-on-mars</nowiki></ref>

Further support for the historic existence of flowing water comes from the first observations made by NASA's [[Mars Reconnaissance Orbiter]] (launched in 2005) where the High Resolution Imaging Science Experiment (HiRISE) camera spotted small fractures and cracks in the Martian canyon, [[Candor Chasma]]. The cracks analyzed show signs of mineral alteration in the rock exposed - a sign that liquid water once flowed through these sub-surface pipes.

:"''What caught my eye was the bleaching or lack of dark material along the fracture. That is a sign of mineral alteration by fluids that moved through those joints. It reminded me of something I had seen during field studies in Utah, that is light-tone zones, or 'haloes,' on either side of cracks through darker sandstone''" - Dr. Chris Okubo, a geologist at the University of Arizona, Tucson.

Although this is a sign that the liquid water has since disappeared from these cracks and fractures in the canyon rock, it is interesting to find evidence for ancient water in abundance.

=== Current water ice ===
Around the same time the [[Mars Express]] orbiter detected the spectral evidence of water present in the polar regions. In 2005, Mars Express confirmed this by locating an area of solid water ice near the north pole. The [[Phoenix]] lander confirmed the existence of water ice in Mars.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref>

Photos from the [[Mars Reconnaissance Orbiter]] show frozen water just below the Martian surface (see photograph). Surprisingly the location is far away from the poles (43.28 degrees north latitude, 164.22 degrees east longitude), which raises the hope of large amounts of water all over the planet.
<ref>[http://www.nasa.gov/mission_pages/MRO/news/mro20090924.html Mars Reconnaissance Orbiter Sees Ice Exposed by Meteor Impact]</ref>

====Abundance====
[[Image:MARSIS.jpg|thumb|200px|right|A MARSIS map of Mars' south pole ice deposits.]]
On March 15, 2007, [[Mars Express]]' mission control released more news of extensive frozen water discovered at the Martian [[south pole]]. These new and highly accurate measurements predict that if the ice were to be melted, the whole planet would be covered in a liquid layer 11 meters deep. Although it has been known for many years that the poles have an abundance of ice, it has never been measured to this degree of accuracy. The data comes from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) currently mapping the north pole to gain a better understanding of how much frozen water may be contained there. MARSIS can probe over 2 miles below the Martian surface and has found extensive layered deposits of ice.

Mars shows evidence of extensive liquid water flowing on its surface in the past and it is the focus of many Mars missions to find out how this water has leaked away over the millennia. Martian polar ice may be the culprit, suggesting Mars may once have had a warmer climate, slowly cooling as the atmosphere became a more inefficient insulator for the meager heating from the distant Sun.

===Current liquid water===

Future manned exploration on Mars will require a source of water whether it is in the form of ice or sub-surface [[aquifers]]. The [[Mars Express]] orbiter has uncovered some confusing measurements suggesting there may be liquid water accompanying all that ice. MARSIS bounced back data suggesting at least 90% of the layered deposits under the polar cap are indeed supplies of ice, but a thin layer resembling liquid water is also evident. It is hard to understand the existence of liquid water at the extremely low temperatures predicted. Perhaps high pressures or small geological processes may explain these observations. Another orbiter, NASA's Mars Global Surveyor, has also returned some exciting new evidence for the existence of new flows of liquid water on the Martian surface away from the frozen poles. {{science question|What pressures are required to keep water in a liquid phase at temperatures as low as that on the surface of Mars? - [[User:Ioneill|Ioneill]]}}

The [[Mars Global Surveyor]] arrived at the Red Planet on September 11, 1997 and returned a decade of data on the evolution of the planet before it was lost in November 2006 through energy loss. It was Mars' longest operational artificial satellite. The Mars Orbiter Camera (MOC) onboard revealed new deposits possibly carried as sediment by flowing water in two locations in the past 7 years (press release dated December 6, 2006)<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref>. In images taken in August 1999 and September 2006 of the same location ([[Centauri Montes]] Region), a bright deposit measuring several hundred meters long is evident in the 2006 image but not in the 1999 image. A similar feature was observed at a different location from 2001 to 2005 at [[Terra Sirenum]]. It is worth noting that both locations are in equatorial regions, not usually associated with ice or liquid water. This suggests liquid water remains a characteristic of the Mars landscape, if only sporadically. These discoveries have increased the enthusiasm for the search for [[microbes|microbial life]], but the implications for manned exploration are huge. If there are pockets of liquid water just below the surface, Mars may yet be able to provide our future pioneers with natural springs more familiar on Earth.
[[Image:Water_deposit.jpg|thumb|left|200px|Evidence from the [[Mars Global Surveyor]] MOC instrument that spurts of liquid water may sporadically flow on the Martian surface]]
However, surface water on Mars is short-lived. The Martian atmosphere is very thin (a pressure of 7 millibars, <1% that of Earth's thick atmosphere) and cold (an average global temperature of -55°C or -67F), these two factors deny any long-term existence of liquid water. Surface liquid water will quickly freeze and [[sublimation|sublime]] into the atmosphere, bypassing the [[triple point|liquid phase]]. This phase transition for water on Mars is much like the phase transition for liquid carbon dioxide on Earth when it is released from a CO2 fire extinguisher to produce dry ice snow and CO2 gas. The phase transition for H2O on the surface of Mars occurs below the "[[triple point]]" on the phase diagram so the recent observations of sediment on the surface will have been deposited very quickly by short lived "spurts" of water. Just how short-lived these spurts of water are it is unknown, but a significant volume must have created a formidable river to carry sediment several hundred meters.

At times, the humidity of the Martian atmosphere can reach 100% (at Mars' temperature and pressure). If the temperature was high, salty brines could last several minutes on the Martian surface.

Although there may be other explanations for these long "channels" of sediment, such as rock slides or wind-blown [[sand]] features, the appearance of the deposits seem very water-like. Michael Malin of Malin Space Science Systems, a mission scientist for the MOC says, "''The shapes of these deposits are what you would expect to see if the material were carried by flowing water... they have finger-like branches at the downhill end and easily diverted around small obstacles''".<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref> It is also possible that other liquids such as 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 1,3-propanediol, ethylene glycol and related liquids could be responsible for [[Recent Liquid Flow on Mars|fluid flow features]] on Mars. While such liquids would be relatively more rare than water, the resistance to freezing of such liquids and mixtures of such liquids with water would allow them to cause fluid flow effects where pure liquid water is impossible.

==Water production==
Water production on Mars for settlement use or for exploration uses can take many forms. As a prime [[In-situ resource utilization|In-situ]] resource the presence of water on Mars is one of its main attractions. Further exploration is needed to determine if the water is available in a relatively pure form, or if it will contain salts and other chemical contaminants requiring water treatment.

===Atmosphere===
The Martian [[atmosphere]] contains water vapour (which on occasion can reach 100% humidity). However, it is normally dry and very thin, which makes extracting water slow and energy intensive. With a device similar to an [[atmospheric mining|air dehumidifier]] the production of water should be feasible all over the planet's surface. An [[experimental setup#water out of the atmosphere|experimental setup]] is necessary to find out all about the viability of this approach.

===Caves===
Since the discovery of [[caves]] scientists believe in the possibility of water ice on the ground of the caves. Water ice is abundant under the ground at least near the poles, and probably elsewhere too.

===Glaciers===
The [[Mars Reconnaissance Orbiter]] has found evidence of [[glacier|glaciers]] covered in regolith.<ref>http://www.nasa.gov/home/hqnews/2008/nov/HQ_08-304_MRO_BuriedGlaciers.html</ref> Radar reflection data indicates that these are not Rock Glaciers that have been previously suspected on Mars, but instead are thick glacial ice covered in a thin layer of debris. The buried glaciers lie in the [[Hellas Planitia|Hellas Basin]] region of Mars' southern hemisphere with similar aprons detected extending from cliffs in the northern hemisphere.

===Regolith===
Water is present in the martian regolith both as ice and as hydrated minerals. In addition, a recent paper has shown that a huge amount of water has been absorbed by rocks. On Earth, plate Tectonics takes these hydrated minerals and melts them, where water can return to the surface via vulcanism. On Mars the water remains in these minerals. <ref>https://science.sciencemag.org/content/early/2021/03/15/science.abc7717 - Long term drying of Mars by sequestration of Ocean-scale volumes of water in the crust</ref>

===Polar regions===
The martian polar regions have extensive ice caps as well as ice filled craters, such as the [[Korolev]] crater, that could serve as water sources. As the poles are usually extremely cold, sources closer to the equator would be more useful for future martian settlements. Note that permafrost has been detected at all latitudes, but above 30 degrees latitude, surface ice is found fairly often.

==Uses==

===Drinking water===
The [[human]] metabolism requires a regular intake of fresh water. Pure liquid water is non-existent on Mars but there is abundant frozen water and hydrated minerals. Since getting liquid water for use will require some industrial effort, the [[recycling]] of all excretion would provide advantages in reducing water use. There are two ways: Wastewater can be [[Potable_water_treatment|treated]], which is partially done on the [[ISS]] already. Alternatively, the water can be kept in a nearly natural cycle, using parts of the [[greenhouse]]s for [[biological wastewater treatment]].

The concentration of deuterium in Martian hydrogen and thus in Martian water is between five and thirteen ten-thousandth-parts.<ref>[http://www.sciencemag.org/content/240/4860/1767.abstract abstract in ''Science'']</ref> or about six times the relative abundance on Earth. Still this concentration is far from the 25% of the body's content of hydrogen that would need to be substituted by deuterium before there are any serious health effects. Deuterium is not a cumulative poison. At about one thousandth part of the hydrogen in Martian water, deuterium would be excreted as fast as it is consumed and would not be a health problem.

===Industrial processes===

Many industrial processes considered for a Mars settlement, in particular the production of [[methanol]] and [[methane]] and other hydrocarbons require hydrogen. This can be obtained by [[electrolysis]] or via thermolysis such as the Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2006.05.013</ref> or the Zinc/Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2015.11.049</ref>. In electrolysis or basic thermolysis, [[Oxygen O2]] is produced as a byproduct. In the Zinc/Sulfur/Iodine cycle, CO2 and H2O are inputs and the outputs are CO and H2. CO is industrially useful in the production of [[methanol]] and other [[Hydrocarbon_synthesis|hydrocarbons]], as well as in mineral refining via the [https://en.wikipedia.org/wiki/Mond_process Mond process]. The H2 can also be combined with atmospheric N2 using a [https://en.wikipedia.org/wiki/Haber_process Haber reactor] to produce [[ammonia]].

Most other processes require the use of significant quantities of water as a [[solvent]] for reagents such as [[acid]]s or [[ammonia]] or a a coolant for high temperature systems.

Power sources which rely on heat engines (such as [[nuclear power]]) require a heat sink to provide the heat differential required for the engine to run. Water or Ice make good materials for this heat sink as they are dense and have high thermal mass. The ice of [[korolev|Korolev Crater]] has been suggested as a potential heat sink sufficient to provide for colony scale power generation.

[[Deuterium]] from martian water may provide a source of fusion fuel for future energy production. Note that deuterium is 2.5 times more concentrated on Mars than on Earth, and may form a viable export.

[[Methanol]] and [[methane]] may be used to feed [[Biological_reactors|methanotrophs]] to produce food or other biologically produced industrial materials.

==See Also==

*[[Martian features that are signs of water ice]]
*[[Sublimation]]
*[[Water Infrastructure|Water infrastructure]] and waste water treatment
*"Mars: A Warmer Wetter Planet", by Jeffrey S. Kargel, ISBN 1-85233-568-8.

==External links==

*[https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

*[http://en.wikipedia.org/wiki/Water Wikipedia page on water]
*[http://mars.jpl.nasa.gov/express/mission/sc_science_marsis02.html Searching for water with the Mars Express MARSIS instrument.]
*[https://en.wikipedia.org/wiki/Water_on_Mars Wikipedia page on water on Mars]

*[https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

===References===
<references />

Imaging Spectroscopy

2021-07-12T20:02:43Z

JimL:

Regular cameras record light intensity at 3 wavelengths (red, green, and blue), which is sufficient to produce an image the looks accurate to the human eye. In imaging spectroscopy, a camera measures the intensity of light at more than just 3 different wavelengths. For every pixel in the photograph, the camera records data that can be viewed as a graph showing how the intensity of light varies across the visible region of the electromagnetic spectrum (and sometimes beyond the visible region). That graph can reveal details about the chemical makeup and physical properties of the photographed object.

Imaging spectroscopy has been used by telescopes and spacecraft to study Mars.

Reflectance spectroscopy and thermal emission spectroscopy are two types of imaging spectroscopy.

==Reflectance Spectroscopy==
Reflectance spectroscopy measures the visible and infrared light spectrum of the sunlight reflected from an object. After the spectrum of the light emitted by the sun is taken into account, a spectrum that is specific to the reflecting material is calculated. This spectrum can be compared to a library of known spectra.<ref>Shaw GA & Burke HK. 2003. Spectral Imaging for Remote Sensing. Lincoln Laboratory Journal, 14(1), 3-28. <nowiki>https://courses.cs.washington.edu/courses/cse591n/07sp/papers/Shaw2003.pdf</nowiki></ref> The [[Mars Express]] Orbiter uses an imaging spectrometer named Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) to study the elements and minerals present on the surface of Mars.<ref>The European Space Agency. Mars Express orbiter instruments. <nowiki>http://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_instruments</nowiki></ref> OMEGA's detection of hydrated minerals in 2005 was, at the time, the strongest evidence that surface water was once present in large amounts and for a long duration.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #1. Hydrated minerals – evidence of liquid water on Mars. <nowiki>https://sci.esa.int/web/mars-express/-/51821-1-hydrated-minerals-ndash-evidence-of-liquid-water-on-mars</nowiki></ref> The Compact Reconnaissance Imaging Spectrometer for Mars, an instrument on the [[Mars Reconnaissance Orbiter]], uses reflectance spectroscopy to examine the surface and dust in the atmosphere. Among other findings, it was used to better understand how dust warms the Martian atmosphere by absorbing sunlight.<ref>Johns Hopkins Applied Physics Laboratory. CRISM's Investigations and New Discoveries (2006-present). <nowiki>http://crism.jhuapl.edu/science/themes/index.php</nowiki></ref>

==Thermal Emission Spectroscopy==
Thermal emission spectroscopy, also known as infrared imaging, measures the infrared light that is released by any object as a result of normal molecular vibrations. The spectrum of this light provides information on the composition of the object that emitted it, and that object's temperature. The Thermal Emission Spectrometer on [[Mars Global Surveyor]] used thermal emission spectroscopy to learn about dust in the Martian atmosphere and the surface temperature on Mars.<ref>Arizona State University. Mars Global Surveyor Thermal Emission Spectrometer. <nowiki>http://tes.asu.edu/index.html</nowiki></ref> The Thermal Infrared Imaging Spectrometer on the [[Mars Orbiter Mission]] spacecraft also uses this technique.<ref>Indian Space Research Organization. Payloads. In ''PSLV-C25/Mars Orbiter Mission''. <nowiki>https://www.isro.gov.in/pslv-c25-mars-orbiter-mission/payloads</nowiki></ref>
==Multispectral Imaging==
It is also possible for a single instrument to combine both of the above methods to perform multispectral imaging. The Thermal Emission Imaging System on [[Mars Odyssey]] is capable of multispectral imaging.<ref>Arizona State University School of Earth & Space Exploration. Frequently Asked Questions. In ''Mars Odyssey THEMIS''. <nowiki>http://themis.asu.edu/faq</nowiki></ref>

==External Links==
Compact Reconnaissance Imaging Spectrometer for Mars web site: http://crism.jhuapl.edu/index.php

Library of thermal infrared spectra maintained by Arizona State University's Mars Space Flight Facility: https://speclib.asu.edu/

==References==
<references />

Needed Articles

2021-05-17T20:56:48Z

JimL:

This is the global collection of articles that are needed by [[Marspedia]] and shall be a guide for authors, who want to start new articles without knowing which direction to go. Articles with existing links may need expansion.

The [[:Category:Bootstrap lists|Bootstrap lists]] offers an alternative path to lists of articles than need be upgraded.
==Mars Planetary Science==

*List of Mars Calendars
*[[Mars orbit|Mars' Orbital Position]]
*[[Areomorphology|Martian "Geomorphology". What processes have shaped Mars?]]
*[[Mars surface features|What are the different topologies on Mars?]]
*[[Dust storms|Global dust storms]]
*What is the date on Mars? What year/season/month is it?
*Upper atmosphere chemical processes
*[[Gravity|What do the differences in gravity show us?]]
*[[Imaging Spectroscopy|Reflectance and emission spectroscopy]]
*Mineral identification from satellite, balloon, and aircraft carried instruments
*[[Imaging Spectroscopy|Multispectral and thermal infrared imaging]]
*[[Geological processes that have shaped Mars: Why Mars looks like it does|Geological processes that have shaped Mars]]
*[[In-situ resource utilization|What minerals could be mined on Mars?]]
*[[Mars atlas geology|Mineral spatial distribution]]
*Subsurface water or ice deposits
*Surface ice at poles
*[[Mars Atlas|Surface elevation profiles and maps]]
*[[Martian weather]]
*[[Mars volcanoes]] 'Replace with [[Mars atlas Volcanoes and Craters]]'
*[[Geography of Mars|Martian dichotomy]]
*[[Toponymy of Mars]]
*[[Moons of Mars (Phobos and Deimos)]]
*Organic compounds on Mars
*[[Liquid Water on Mars|Liquid water]]
*[[Magnetosphere|Magnetic field]]

==Mars Spacecraft/Robotic Missions==

*Utility of unmanned missions
*Scientific data (collection/transmission/interpretation)
*Follow the water strategy
*Subsurface search strategy
*On-site organic compound detection
*DNA/RNA analysis chips
*Spectrographic imagery
*Multispectral mineral identification
*Multimission timelines
*Mission sequences
*Current and planned instruments
*[[Spacecraft Classification|Orbital vs. lander vs. robotic exploration]]
*[[Aerobraking|Aerocapture orbits]]
*[[Mars cycler|Earth-Mars cyclers]]
*[[Fuel|Chemical propellants]]
*[[Nuclear thermal propulsion|Nuclear thermal rockets]]
*[[Ion thruster|Ion propulsion]]
*[[Solar concentrator|Solar mirrors]]
*DNA/RNA analysis chips
*[[Interplanetary communications|Mars to Earth communication systems]]
*[[Areostationary orbit|Equatorial stationary satellites (for communication)]]
*Aeropositioning satellites (analagous to GPS)
*Miniaturized chemical/molecular identification systems
*[[Laser communication systems]]
*Advanced sensing
*AI autonomy
*[[3D Printer|3D printing of complex geometries]]
*[[3D Printer|Self-replicating machines]]
*Hybrid machine enhanced biologics
*Exploration missions (list including chronology and instruments)
*Imagery
*Spectroscopy
*[[Interplanetary communications|Communications]]
*Lander mission atmospheric seasonal measurements
*Subsurface drilling and chemical analysis
*Degrees of autonomy
*[[Research|Regolith sampling and mineral identification]]

==Mars Human Exploration==

*[[Transport from Earth to Mars|Transport options]]
*[[Perchlorate|Perchlorates in regolith]]
*Mars Direct rockets
*Reverse thrust rockets
*[[Landing on Mars|Parachute-assisted descent vehicles]]
*[[Fuel|Methane-oxygen rockets]]
*Aerology and minerology mapping
*[[EVA Suit|Hybrid hard shell EVA suits]]
*[[EVA Suit|Skin-tight mechanical counterpressure suits]]
*[[Funding]]: International, national, and commercial
*Human factors in crew selection
*[[Radiation|Radiation protection: in transit and for exploration missions]]
*Physical fitness for exploration missions
*Cross training in skill sets
*[[Gravity|Health effects of microgravity]]
*Psychological stressors in transit
*Medical training for exploration teams
*Medical equipment for exploration teams
*[[Exobiology|Search for life]]
*[[Atmospheric processing|Oxygen from CO2 atmosphere]]
*[[Atmospheric processing|Organic chemicals and fuel from atmosphere]]
*Exploration and science in simulated marssuits
*Long-duration missions
*Human factors studies

==Mars Human Settlement==

*[[Settlement facilities]]
*[[Transportation|Inter-settlement transportation]]
*[[Rovers|Exploration rovers and rover assistants]]
*[[Starship|Falcon Heavy for nonhuman payloads]]
*[[Starship|Big Falcon Rocket for human/nonhuman payloads]]
*[[Life support|Biosystems to maintain 02/CO2 ratio]]
*[[Water Infrastructure|Distribution of water (liquid and ice) on Mars]]
*[[Potable water treatment|Impurities in water on Mars]]
*[[Settlement|Size and specialization of settlements]]
*[[List of martian products|Manufactured products]]
*[[Martian architecture|Architecture of buildings]]
*[[Transportation|Wheeled vs. railed surface transportation]]
*[[Food|Will Martians eat meat?]]
*[[Settlement systems|How will the Martians communicate across the planet?]]
*[[Energy|Total thermal energy need per capita]]
*[[Energy|Total electrical need per capita]]
*[[Food|100% Mars-sourced food production]]
*Crop choices influenced by ability to thrive in Mars environments
*[[ISRU timeline|The listing and timing of materials produced from Mars resources]]
*[[3D Printer|Additive manufacture (incl. 3D printing)]]
*Will individual settlements establish their own societal rules?
*[[Land|Who owns Mars?]]
*[[Interplanetary commerce|Mars, LEO, Moon trade triangle]]
*[[Terraforming|Increase in pressure needed to allow standing liquid pure water on surface]]
*[[Terraforming|Increase in surface temperature to partially melt polar ice caps]]

==Mars Outreach==

*Mars Society chapters
*Mars Society conferences
*MDRS crews
*Mars Society projects
*Mars Society goals
*[[Mars Foundation]]: About the organization
*[[Hillside settlement]]
*[[Plains settlement]]
*About Marspedia
*The Goals of Marspedia
*Explore Mars
*Mars One
*Mars Journal

==Mars Arts and Literature==

*[[List of books set on Mars|chronology of Mars science fiction]]
*lists of Mars science fiction by plot-line focus
*List of plays
*[[List of movies]]
*List of documentaries
*List of TV Series
*List of computer games
*List of board games
*Accuracy of depiction of Mars in popular culture

Laser communication systems

2021-05-17T20:55:32Z

JimL:

Lasers could one day carry communication signals between Earth and Mars.

Current Mars rovers and satellites send and receive signals from Earth via radio waves at a data rate of a few megabits per second<ref name=":0">Carter, J., 2020, NASA Will Soon Use 'Space Lasers' To Give Us Live Video From Mars And The Moon, ''Forbes'', <nowiki>https://www.forbes.com/sites/jamiecartereurope/2020/02/11/how-space-lasers-will-bring-the-solar-system-its-broadband-moment-and-live-video-from-mars</nowiki>.</ref>. If lasers could be used instead, the transmission would form a tighter beam, with more of the total energy being delivered to the receiving antenna and less wasted. This means a higher data rate, for the same power consumption<ref name=":1">Seffers, G.I., 2018, NASA Counts Down to Laser Communications for Mars, ''SIGNAL Magazine'', <nowiki>https://www.afcea.org/content/nasa-counts-down-laser-communications-mars</nowiki>.</ref>. With current technology, at Earth-Mars range, a laser could increase bandwidth by a factor of 10 compared to radio waves, making high-definition video streams possible. Future refinements in the technology could lead to a data rate 100 times that of radio waves<ref name=":0" />.

Laser communication has never been tried at this distance. NASA plans to test long-distance communication using an infrared laser in conjunction with an upcoming [https://www.nasa.gov/mission_pages/tdm/dsoc/index.html mission] that will send a probe to an asteroid, scheduled to launch in 2022 and arrive at its destination in 2026.

A new [[Deep Space Network]] antenna currently under construction will have dual functionality for both radio and laser signals<ref name=":0" />.

Engineering challenges for Earth-Mars laser communication include interference from sunlight, precise pointing of the narrow beam despite spacecraft motion and vibrations<ref name=":1" />, interference from Earth's atmosphere, space temperature extremes, radiation, and forces on delicate equipment during launch<ref name=":0" />.

==References==
<references />

Laser communication systems

2021-05-17T20:53:01Z

JimL:

Lasers could one day carry communication signals between Earth and Mars.

Current Mars rovers and satellites send and receive signals from Earth via radio waves at a data rate of a few megabits per second<ref name=":0">Carter, J., 2020, NASA Will Soon Use 'Space Lasers' To Give Us Live Video From Mars And The Moon, ''Forbes'', <nowiki>https://www.forbes.com/sites/jamiecartereurope/2020/02/11/how-space-lasers-will-bring-the-solar-system-its-broadband-moment-and-live-video-from-mars</nowiki>.</ref>. If lasers could be used instead, the transmission would form a tighter beam, with more of the total energy being delivered to the receiving antenna and less wasted. This means a higher data rate, for the same power consumption<ref name=":1">Seffers, G.I., 2018, NASA Counts Down to Laser Communications for Mars, ''SIGNAL Magazine'', <nowiki>https://www.afcea.org/content/nasa-counts-down-laser-communications-mars</nowiki>.</ref>. With current technology, at Earth-Mars range, a laser could increase bandwidth by a factor of 10 compared to radio waves, making high-definition video streams possible. Future refinements in the technology could lead to a data rate 100 times that of radio waves<ref name=":0" />.

Laser communication has never been tried at this distance. NASA plans to test long-distance communication using an infrared laser in conjunction with an upcoming [https://www.nasa.gov/mission_pages/tdm/dsoc/index.html mission] that will send a probe to an asteroid, scheduled to launch in 2022 and arrive at its destination in 2026.

A new Deep Space Network antenna currently under construction will have dual functionality for both radio and laser signals<ref name=":0" />.

Engineering challenges for Earth-Mars laser communication include interference from sunlight, precise pointing of the narrow beam despite spacecraft motion and vibrations<ref name=":1" />, interference from Earth's atmosphere, space temperature extremes, radiation, and forces on delicate equipment during launch<ref name=":0" />.

== References ==
<references />

Laser communication systems

2021-05-17T20:52:22Z

JimL: Created page with "Lasers could one day carry communication signals between Earth and Mars. Current Mars rovers and satellites send and receive signals from Earth via radio waves at a data rate..."

Lasers could one day carry communication signals between Earth and Mars.

Current Mars rovers and satellites send and receive signals from Earth via radio waves at a data rate of a few megabits per second<ref name=":0">Carter, J., 2020, NASA Will Soon Use 'Space Lasers' To Give Us Live Video From Mars And The Moon, ''Forbes'', <nowiki>https://www.forbes.com/sites/jamiecartereurope/2020/02/11/how-space-lasers-will-bring-the-solar-system-its-broadband-moment-and-live-video-from-mars</nowiki>.</ref>. If lasers could be used instead, the transmission would form a tighter beam, with more of the total energy being delivered to the receiving antenna and less wasted. This means a higher data rate, for the same power consumption<ref name=":1">Seffers, G.I., 2018, NASA Counts Down to Laser Communications for Mars, ''SIGNAL Magazine'', <nowiki>https://www.afcea.org/content/nasa-counts-down-laser-communications-mars</nowiki>.</ref>. With current technology, at Earth-Mars range, a laser could increase bandwidth by a factor of 10 compared to radio waves, making high-definition video streams possible. Future refinements in the technology could lead to a data rate 100 times that of radio waves<ref name=":0" />.

Laser communication has never been tried at this distance. NASA plans to test long-distance communication using an infrared laser in conjunction with an upcoming [https://www.nasa.gov/mission_pages/tdm/dsoc/index.html mission] that will send a probe to an asteroid, scheduled to launch in 2022 and arrive at its destination in 2026.

A new Deep Space Network antenna currently under construction will have dual functionality for both radio and laser signals<ref name=":0" />.

Engineering challenges for Earth-Mars laser communication include interference from sunlight, precise pointing of the narrow beam despite spacecraft motion and vibrations<ref name=":1" />, interference from Earth's atmosphere, space temperature extremes, radiation, and forces on delicate equipment during launch<ref name=":0" />.

Needed Articles

2021-02-22T23:34:23Z

JimL:

This is the global collection of articles that are needed by [[Marspedia]] and shall be a guide for authors, who want to start new articles without knowing which direction to go. Articles with existing links may need expansion.

The [[:Category:Bootstrap lists|Bootstrap lists]] offers an alternative path to lists of articles than need be upgraded.
==Mars Planetary Science==

*List of Mars Calendars
*[[Mars orbit|Mars' Orbital Position]]
*[[Areomorphology|Martian "Geomorphology". What processes have shaped Mars?]]
*[[Mars surface features|What are the different topologies on Mars?]]
*[[Dust storms|Global dust storms]]
*What is the date on Mars? What year/season/month is it?
*Upper atmosphere chemical processes
*[[Gravity|What do the differences in gravity show us?]]
*[[Imaging Spectroscopy|Reflectance and emission spectroscopy]]
*Mineral identification from satellite, balloon, and aircraft carried instruments
*[[Imaging Spectroscopy|Multispectral and thermal infrared imaging]]
*[[Geological processes that have shaped Mars: Why Mars looks like it does|Geological processes that have shaped Mars]]
*[[In-situ resource utilization|What minerals could be mined on Mars?]]
*[[Mars atlas geology|Mineral spatial distribution]]
*Subsurface water or ice deposits
*Surface ice at poles
*[[Mars Atlas|Surface elevation profiles and maps]]
*[[Martian weather]]
*[[Mars volcanoes]] 'Replace with [[Mars atlas Volcanoes and Craters]]'
*[[Geography of Mars|Martian dichotomy]]
*[[Toponymy of Mars]]
*[[Moons of Mars (Phobos and Deimos)]]
*Organic compounds on Mars
*[[Liquid Water on Mars|Liquid water]]
*[[Magnetosphere|Magnetic field]]

==Mars Spacecraft/Robotic Missions==

*Utility of unmanned missions
*Scientific data (collection/transmission/interpretation)
*Follow the water strategy
*Subsurface search strategy
*On-site organic compound detection
*DNA/RNA analysis chips
*Spectrographic imagery
*Multispectral mineral identification
*Multimission timelines
*Mission sequences
*Current and planned instruments
*[[Spacecraft Classification|Orbital vs. lander vs. robotic exploration]]
*[[Aerobraking|Aerocapture orbits]]
*[[Mars cycler|Earth-Mars cyclers]]
*[[Fuel|Chemical propellants]]
*[[Nuclear thermal propulsion|Nuclear thermal rockets]]
*[[Ion thruster|Ion propulsion]]
*[[Solar concentrator|Solar mirrors]]
*DNA/RNA analysis chips
*[[Interplanetary communications|Mars to Earth communication systems]]
*[[Areostationary orbit|Equatorial stationary satellites (for communication)]]
*Aeropositioning satellites (analagous to GPS)
*Miniaturized chemical/molecular identification systems
*Laser communication systems
*Advanced sensing
*AI autonomy
*[[3D Printer|3D printing of complex geometries]]
*[[3D Printer|Self-replicating machines]]
*Hybrid machine enhanced biologics
*Exploration missions (list including chronology and instruments)
*Imagery
*Spectroscopy
*[[Interplanetary communications|Communications]]
*Lander mission atmospheric seasonal measurements
*Subsurface drilling and chemical analysis
*Degrees of autonomy
*[[Research|Regolith sampling and mineral identification]]

==Mars Human Exploration==

*[[Transport from Earth to Mars|Transport options]]
*[[Perchlorate|Perchlorates in regolith]]
*Mars Direct rockets
*Reverse thrust rockets
*[[Landing on Mars|Parachute-assisted descent vehicles]]
*[[Fuel|Methane-oxygen rockets]]
*Aerology and minerology mapping
*[[EVA Suit|Hybrid hard shell EVA suits]]
*[[EVA Suit|Skin-tight mechanical counterpressure suits]]
*[[Funding]]: International, national, and commercial
*Human factors in crew selection
*[[Radiation|Radiation protection: in transit and for exploration missions]]
*Physical fitness for exploration missions
*Cross training in skill sets
*[[Gravity|Health effects of microgravity]]
*Psychological stressors in transit
*Medical training for exploration teams
*Medical equipment for exploration teams
*[[Exobiology|Search for life]]
*[[Atmospheric processing|Oxygen from CO2 atmosphere]]
*[[Atmospheric processing|Organic chemicals and fuel from atmosphere]]
*Exploration and science in simulated marssuits
*Long-duration missions
*Human factors studies

==Mars Human Settlement==

*[[Settlement facilities]]
*[[Transportation|Inter-settlement transportation]]
*[[Rovers|Exploration rovers and rover assistants]]
*[[Starship|Falcon Heavy for nonhuman payloads]]
*[[Starship|Big Falcon Rocket for human/nonhuman payloads]]
*[[Life support|Biosystems to maintain 02/CO2 ratio]]
*[[Water Infrastructure|Distribution of water (liquid and ice) on Mars]]
*[[Potable water treatment|Impurities in water on Mars]]
*[[Settlement|Size and specialization of settlements]]
*[[List of martian products|Manufactured products]]
*[[Martian architecture|Architecture of buildings]]
*[[Transportation|Wheeled vs. railed surface transportation]]
*[[Food|Will Martians eat meat?]]
*[[Settlement systems|How will the Martians communicate across the planet?]]
*[[Energy|Total thermal energy need per capita]]
*[[Energy|Total electrical need per capita]]
*[[Food|100% Mars-sourced food production]]
*Crop choices influenced by ability to thrive in Mars environments
*[[ISRU timeline|The listing and timing of materials produced from Mars resources]]
*[[3D Printer|Additive manufacture (incl. 3D printing)]]
*Will individual settlements establish their own societal rules?
*[[Land|Who owns Mars?]]
*[[Interplanetary commerce|Mars, LEO, Moon trade triangle]]
*[[Terraforming|Increase in pressure needed to allow standing liquid pure water on surface]]
*[[Terraforming|Increase in surface temperature to partially melt polar ice caps]]

==Mars Outreach==

*Mars Society chapters
*Mars Society conferences
*MDRS crews
*Mars Society projects
*Mars Society goals
*[[Mars Foundation]]: About the organization
*[[Hillside settlement]]
*[[Plains settlement]]
*About Marspedia
*The Goals of Marspedia
*Explore Mars
*Mars One
*Mars Journal

==Mars Arts and Literature==

*[[List of books set on Mars|chronology of Mars science fiction]]
*lists of Mars science fiction by plot-line focus
*List of plays
*[[List of movies]]
*List of documentaries
*List of TV Series
*List of computer games
*List of board games
*Accuracy of depiction of Mars in popular culture

Imaging Spectroscopy

2021-02-22T23:32:09Z

JimL:

In imaging spectroscopy, a photograph is taken in a way that measures the intensity of light at a number of different wavelengths. This process generates a separate light spectrum for every pixel in the photograph.

Imaging spectroscopy can be used by telescopes and spacecraft to study Mars.

Reflectance spectroscopy and thermal emission spectroscopy are two types of imaging spectroscopy.

==Reflectance Spectroscopy==
Reflectance spectroscopy measures the visible and infrared light spectrum of the sunlight reflected from an object. After the spectrum of the light emitted by the sun is taken into account, a spectrum that is specific to the reflecting material is calculated. This spectrum can be compared to a library of known spectra.<ref>Shaw GA & Burke HK. 2003. Spectral Imaging for Remote Sensing. Lincoln Laboratory Journal, 14(1), 3-28. <nowiki>https://courses.cs.washington.edu/courses/cse591n/07sp/papers/Shaw2003.pdf</nowiki></ref> The Compact Reconnaissance Imaging Spectrometer for Mars, an instrument on the [[Mars Reconnaissance Orbiter]], uses reflectance spectroscopy to identify minerals on the surface of Mars.<ref>Johns Hopkins Applied Physics Laboratory. Compact Reconnaissance Imaging Spectrometer for Mars. <nowiki>http://crism.jhuapl.edu/index.php</nowiki></ref>

== Thermal Emission Spectroscopy ==
Thermal emission spectroscopy, also known as infrared imaging, measures the infrared light that is released by any object as a result of normal molecular vibrations. The spectrum of this light provides information on the composition of the object that emitted it, and that object's temperature. The Thermal Emission Spectrometer on [[Mars Global Surveyor]] used thermal emission spectroscopy to learn about dust in the Martian atmosphere and the surface temperature on Mars.<ref>Arizona State University. Mars Global Surveyor Thermal Emission Spectrometer. <nowiki>http://tes.asu.edu/index.html</nowiki></ref> The Thermal Infrared Imaging Spectrometer on the [[Mars Orbiter Mission]] spacecraft also uses this technique.<ref>Indian Space Research Organization. Payloads. In ''PSLV-C25/Mars Orbiter Mission''. <nowiki>https://www.isro.gov.in/pslv-c25-mars-orbiter-mission/payloads</nowiki></ref>

== Multispectral Imaging ==
It is also possible for a single instrument to combine both of the above methods to perform multispectral imaging. The Thermal Emission Imaging System on [[Mars Odyssey]] is capable of multispectral imaging.<ref>Arizona State University School of Earth & Space Exploration. Frequently Asked Questions. In ''Mars Odyssey THEMIS''. <nowiki>http://themis.asu.edu/faq</nowiki></ref>

== External Links ==
Library of thermal infrared spectra maintained by Arizona State University's Mars Space Flight Facility: https://speclib.asu.edu/

==References==
<references />

Mars atlas geology

2020-12-20T17:28:01Z

JimL:

<imagemap>

File:Generalised Geological Map of Mars.jpg|left|thumb|700x900px|Move the Mouse over the image and click on the region you want to see close up.

rect 70 80 2370 200 [[Mare Boreum quadrangle|Mare Boreum]]

rect 1380 310 1420 360[[Lyot Crater]]
rect 2160 490 2190 520[[Hecates Tholus]]

rect 70 200 445 520[[Diacria quadrangle|Diacria]]
rect 444 200 840 520[[Arcadia quadrangle|Arcadia]]
rect 840 200 1210 520[[Mare Acidalium quadrangle|Mare Acidalium]]
rect 1210 200 1600 520[[Ismenius Lacus quadrangle|Ismenius Lacus]]
rect 1600 200 1990 520[[Casius quadrangle|Casius]]
rect 1990 200 2370 520[[Cebrenia quadrangle|Cebrenia]]

rect 320 560 400 630[[Olympus Mons]]
rect 620 760 940 830[[Valles Marineris|Valles Marineris]]
rect 540 720 620 800[[Noctis Labyrinthus|Noctis Labyrinthus]]
rect 2130 540 2190 590[[Elysium Mons|Elysium Mons]]
rect 535 625 565 660[[Ascraeus Mons|Ascraeus Mons]]
rect 480 700 510 740[[Pavonis Mons|Pavonis Mons]]
rect 435 750 470 795[[Arsia Mons|Arsia Mons]]
rect 2340 800 2370 900[[Ma'adim Vallis|Ma'adim Vallis & Gusev crater]]
rect 2080 740 2120 770[[Gale Crater]]

rect 70 520 340 720[[Amazonis quadrangle|Amazonis]]
rect 340 520 630 720[[Tharsis]]
rect 630 520 930 720[[Lunae Palus quadrangle|Lunae Palus]]
rect 930 520 1210 720[[Oxia Palus quadrangle|Oxia Palus]]
rect 1210 520 1500 720[[Arabia quadrangle|Arabia]]
rect 1500 520 1790 720[[Syrtis Major quadrangle|Syrtis Major]]
rect 1790 520 2080 720[[Amenthes quadrangle|Amenthes]]
rect 2080 520 2370 720[[Elysium quadrangle|Elysium]]

rect 70 720 340 920[[Memnonia quadrangle|Memnonia]]
rect 340 720 630 920[[Phoenicis Lacus quadrangle|Phoenicis Lacus]]
rect 630 720 930 920[[Coprates quadrangle|Coprates]]
rect 930 720 1210 920[[Margaritifer Sinus quadrangle|Margaritifer Sinus]]
rect 1210 720 1500 920[[Sinus Sabaeus quadrangle|Sinus Sabaeus]]
rect 1500 720 1790 920[[Iapygia quadrangle|Iapygia]]
rect 1790 720 2080 920[[Mare Tyrrhenum quadrangle|Mare Tyrrhenum]]
rect 2080 720 2370 920[[Aeolis quadrangle|Aeolis]]

rect 70 920 445 1240[[Phaethontis quadrangle|Phaethontis]]
rect 444 920 840 1240[[Thaumasia quadrangle|Thaumasia]]
rect 840 920 1210 1240[[Argyre quadrangle|Argyre]]
rect 1210 920 1600 1240[[Noachis quadrangle|Noachis]]
rect 1600 920 1990 1240[[Hellas quadrangle|Hellas]]
rect 1990 920 2370 1240[[Eridania quadrangle|Eridania]]

rect 70 1240 2370 1400 [[Mare Australe quadrangle|Mare Australe]]

</imagemap>
View a map of:

[[Mars Atlas|General map]]

[[Mars atlas Exploration|Exploration]]

[[Mars atlas Volcanoes and Craters|Volcanoes and Craters]]

[[Mars atlas Quadrangles|Quadrangles]]

[[Mars atlas water|Water abundance]]

[[Mars atlas resources|Resources]]

[[File:USGS-MarsMap-sim3292-20140714-crop.png|USGS-MarsMap-sim3292-20140714-crop]]

== External Links ==
Interactive geological map of Jezero crater: https://planetarymapping.wr.usgs.gov/interactive/sim3464

Mineral abundance maps created using Mars Global Surveyor data: http://www.mars.asu.edu/data/
[[Category:Mars Atlas]]

Needed Articles

2020-11-10T23:41:12Z

JimL:

This is the global collection of articles that are needed by [[Marspedia]] and shall be a guide for authors, who want to start new articles without knowing which direction to go. Articles with existing links may need expansion.

==Mars Planetary Science==

*List of Mars Calendars
*[[Mars orbit|Mars' Orbital Position]]
*[[Areomorphology|Martian "Geomorphology". What processes have shaped Mars?]]
*[[Mars surface features|What are the different topologies on Mars?]]
*[[Dust storms|Global dust storms]]
*What is the date on Mars? What year/season/month is it?
*Upper atmosphere chemical processes
*[[Gravity|What do the differences in gravity show us?]]
*[[Imaging Spectroscopy|Reflectance and emission spectroscopy]]
*Mineral identification from satellite, balloon, and aircraft carried instruments
*Multispectral and thermal infrared imaging
*[[Geological processes that have shaped Mars: Why Mars looks like it does|Geological processes that have shaped Mars]]
*[[In-situ resource utilization|What minerals could be mined on Mars?]]
*[[Mars atlas geology|Mineral spatial distribution]]
*Subsurface water or ice deposits
*Surface ice at poles
*[[Mars Atlas|Surface elevation profiles and maps]]
*Martian weather
*[[Mars volcanoes]] 'Replace with [[Mars atlas Volcanoes and Craters]]'
*[[Geography of Mars|Martian dichotomy]]
*[[Toponymy of Mars]]
*[[Moons of Mars (Phobos and Deimos)]]
*Organic compounds on Mars
*Liquid water
*Magnetic field

==Mars Spacecraft/Robotic Missions==

*Utility of unmanned missions
*Scientific data (collection/transmission/interpretation)
*Follow the water strategy
*Subsurface search strategy
*On-site organic compound detection
*DNA/RNA analysis chips
*Spectrographic imagery
*Multispectral mineral identification
*Multimission timelines
*Mission sequences
*Current and planned instruments
*Orbital vs. lander vs. robotic exploration
*[[Aerobraking|Aerocapture orbits]]
*[[Mars cycler|Earth-Mars cyclers]]
*[[Fuel|Chemical propellants]]
*[[Nuclear thermal propulsion|Nuclear thermal rockets]]
*[[Ion thruster|Ion propulsion]]
*[[Solar concentrator|Solar mirrors]]
*DNA/RNA analysis chips
*[[Interplanetary communications|Mars to Earth communication systems]]
*[[Areostationary orbit|Equatorial stationary satellites (for communication)]]
*Aeropositioning satellites (analagous to GPS)
*Miniaturized chemical/molecular identification systems
*Laser communication systems
*Advanced sensing
*AI autonomy
*[[3D Printer|3D printing of complex geometries]]
*[[3D Printer|Self-replicating machines]]
*Hybrid machine enhanced biologics
*Exploration missions (list including chronology and instruments)
*Imagery
*Spectroscopy
*[[Interplanetary communications|Communications]]
*Lander mission atmospheric seasonal measurements
*Subsurface drilling and chemical analysis
*Degrees of autonomy
*[[Research|Regolith sampling and mineral identification]]

==Mars Human Exploration==

*[[Transport from Earth to Mars|Transport options]]
*[[Perchlorate|Perchlorates in regolith]]
*Mars Direct rockets
*Reverse thrust rockets
*[[Landing on Mars|Parachute-assisted descent vehicles]]
*[[Fuel|Methane-oxygen rockets]]
*Aerology and minerology mapping
*[[EVA Suit|Hybrid hard shell EVA suits]]
*[[EVA Suit|Skin-tight mechanical counterpressure suits]]
*[[Funding]]: International, national, and commercial
*Human factors in crew selection
*[[Radiation|Radiation protection: in transit and for exploration missions]]
*Physical fitness for exploration missions
*Cross training in skill sets
*[[Gravity|Health effects of microgravity]]
*Psychological stressors in transit
*Medical training for exploration teams
*Medical equipment for exploration teams
*[[Exobiology|Search for life]]
*[[Atmospheric processing|Oxygen from CO2 atmosphere]]
*[[Atmospheric processing|Organic chemicals and fuel from atmosphere]]
*Exploration and science in simulated marssuits
*Long-duration missions
*Human factors studies

==Mars Human Settlement==

*[[Settlement facilities]]
*[[Transportation|Inter-settlement transportation]]
*[[Rovers|Exploration rovers and rover assistants]]
*[[Starship|Falcon Heavy for nonhuman payloads]]
*[[Starship|Big Falcon Rocket for human/nonhuman payloads]]
*[[Life support|Biosystems to maintain 02/CO2 ratio]]
*[[Water Infrastructure|Distribution of water (liquid and ice) on Mars]]
*[[Potable water treatment|Impurities in water on Mars]]
*[[Settlement|Size and specialization of settlements]]
*[[List of martian products|Manufactured products]]
*[[Martian architecture|Architecture of buildings]]
*[[Transportation|Wheeled vs. railed surface transportation]]
*[[Food|Will Martians eat meat?]]
*[[Settlement systems|How will the Martians communicate across the planet?]]
*[[Energy|Total thermal energy need per capita]]
*[[Energy|Total electrical need per capita]]
*[[Food|100% Mars-sourced food production]]
*Crop choices influenced by ability to thrive in Mars environments
*[[ISRU timeline|The listing and timing of materials produced from Mars resources]]
*[[3D Printer|Additive manufacture (incl. 3D printing)]]
*Will individual settlements establish their own societal rules?
*[[Land|Who owns Mars?]]
*[[Interplanetary commerce|Mars, LEO, Moon trade triangle]]
*[[Terraforming|Increase in pressure needed to allow standing liquid pure water on surface]]
*[[Terraforming|Increase in surface temperature to partially melt polar ice caps]]

==Mars Outreach==

*Mars Society chapters
*Mars Society conferences
*MDRS crews
*Mars Society projects
*Mars Society goals
*[[Mars Foundation]]: About the organization
*[[Hillside settlement]]
*[[Plains settlement]]
*About Marspedia
*The Goals of Marspedia
*Explore Mars
*Mars One
*Mars Journal

==Mars Arts and Literature==

*[[List of books set on Mars|chronology of Mars science fiction]]
*lists of Mars science fiction by plot-line focus
*List of plays
*[[List of movies]]
*List of documentaries
*List of TV Series
*List of computer games
*List of board games
*Accuracy of depiction of Mars in popular culture

Needed Articles

2020-11-10T23:40:21Z

JimL:

This is the global collection of articles that are needed by [[Marspedia]] and shall be a guide for authors, who want to start new articles without knowing which direction to go. Articles with existing links may need expansion.

==Mars Planetary Science==

*List of Mars Calendars
*[[Mars orbit|Mars' Orbital Position]]
*[[Areomorphology|Martian "Geomorphology". What processes have shaped Mars?]]
*[[Mars surface features|What are the different topologies on Mars?]]
*[[Dust storms|Global dust storms]]
*What is the date on Mars? What year/season/month is it?
*Upper atmosphere chemical processes
*[[Gravity|What do the differences in gravity show us?]]
*[[Imaging spectroscopy|Reflectance and emission spectroscopy]]
*Mineral identification from satellite, balloon, and aircraft carried instruments
*Multispectral and thermal infrared imaging
*[[Geological processes that have shaped Mars: Why Mars looks like it does|Geological processes that have shaped Mars]]
*[[In-situ resource utilization|What minerals could be mined on Mars?]]
*[[Mars atlas geology|Mineral spatial distribution]]
*Subsurface water or ice deposits
*Surface ice at poles
*[[Mars Atlas|Surface elevation profiles and maps]]
*Martian weather
*[[Mars volcanoes]] 'Replace with [[Mars atlas Volcanoes and Craters]]'
*[[Geography of Mars|Martian dichotomy]]
*[[Toponymy of Mars]]
*[[Moons of Mars (Phobos and Deimos)]]
*Organic compounds on Mars
*Liquid water
*Magnetic field

==Mars Spacecraft/Robotic Missions==

*Utility of unmanned missions
*Scientific data (collection/transmission/interpretation)
*Follow the water strategy
*Subsurface search strategy
*On-site organic compound detection
*DNA/RNA analysis chips
*Spectrographic imagery
*Multispectral mineral identification
*Multimission timelines
*Mission sequences
*Current and planned instruments
*Orbital vs. lander vs. robotic exploration
*[[Aerobraking|Aerocapture orbits]]
*[[Mars cycler|Earth-Mars cyclers]]
*[[Fuel|Chemical propellants]]
*[[Nuclear thermal propulsion|Nuclear thermal rockets]]
*[[Ion thruster|Ion propulsion]]
*[[Solar concentrator|Solar mirrors]]
*DNA/RNA analysis chips
*[[Interplanetary communications|Mars to Earth communication systems]]
*[[Areostationary orbit|Equatorial stationary satellites (for communication)]]
*Aeropositioning satellites (analagous to GPS)
*Miniaturized chemical/molecular identification systems
*Laser communication systems
*Advanced sensing
*AI autonomy
*[[3D Printer|3D printing of complex geometries]]
*[[3D Printer|Self-replicating machines]]
*Hybrid machine enhanced biologics
*Exploration missions (list including chronology and instruments)
*Imagery
*Spectroscopy
*[[Interplanetary communications|Communications]]
*Lander mission atmospheric seasonal measurements
*Subsurface drilling and chemical analysis
*Degrees of autonomy
*[[Research|Regolith sampling and mineral identification]]

==Mars Human Exploration==

*[[Transport from Earth to Mars|Transport options]]
*[[Perchlorate|Perchlorates in regolith]]
*Mars Direct rockets
*Reverse thrust rockets
*[[Landing on Mars|Parachute-assisted descent vehicles]]
*[[Fuel|Methane-oxygen rockets]]
*Aerology and minerology mapping
*[[EVA Suit|Hybrid hard shell EVA suits]]
*[[EVA Suit|Skin-tight mechanical counterpressure suits]]
*[[Funding]]: International, national, and commercial
*Human factors in crew selection
*[[Radiation|Radiation protection: in transit and for exploration missions]]
*Physical fitness for exploration missions
*Cross training in skill sets
*[[Gravity|Health effects of microgravity]]
*Psychological stressors in transit
*Medical training for exploration teams
*Medical equipment for exploration teams
*[[Exobiology|Search for life]]
*[[Atmospheric processing|Oxygen from CO2 atmosphere]]
*[[Atmospheric processing|Organic chemicals and fuel from atmosphere]]
*Exploration and science in simulated marssuits
*Long-duration missions
*Human factors studies

==Mars Human Settlement==

*[[Settlement facilities]]
*[[Transportation|Inter-settlement transportation]]
*[[Rovers|Exploration rovers and rover assistants]]
*[[Starship|Falcon Heavy for nonhuman payloads]]
*[[Starship|Big Falcon Rocket for human/nonhuman payloads]]
*[[Life support|Biosystems to maintain 02/CO2 ratio]]
*[[Water Infrastructure|Distribution of water (liquid and ice) on Mars]]
*[[Potable water treatment|Impurities in water on Mars]]
*[[Settlement|Size and specialization of settlements]]
*[[List of martian products|Manufactured products]]
*[[Martian architecture|Architecture of buildings]]
*[[Transportation|Wheeled vs. railed surface transportation]]
*[[Food|Will Martians eat meat?]]
*[[Settlement systems|How will the Martians communicate across the planet?]]
*[[Energy|Total thermal energy need per capita]]
*[[Energy|Total electrical need per capita]]
*[[Food|100% Mars-sourced food production]]
*Crop choices influenced by ability to thrive in Mars environments
*[[ISRU timeline|The listing and timing of materials produced from Mars resources]]
*[[3D Printer|Additive manufacture (incl. 3D printing)]]
*Will individual settlements establish their own societal rules?
*[[Land|Who owns Mars?]]
*[[Interplanetary commerce|Mars, LEO, Moon trade triangle]]
*[[Terraforming|Increase in pressure needed to allow standing liquid pure water on surface]]
*[[Terraforming|Increase in surface temperature to partially melt polar ice caps]]

==Mars Outreach==

*Mars Society chapters
*Mars Society conferences
*MDRS crews
*Mars Society projects
*Mars Society goals
*[[Mars Foundation]]: About the organization
*[[Hillside settlement]]
*[[Plains settlement]]
*About Marspedia
*The Goals of Marspedia
*Explore Mars
*Mars One
*Mars Journal

==Mars Arts and Literature==

*[[List of books set on Mars|chronology of Mars science fiction]]
*lists of Mars science fiction by plot-line focus
*List of plays
*[[List of movies]]
*List of documentaries
*List of TV Series
*List of computer games
*List of board games
*Accuracy of depiction of Mars in popular culture

Imaging Spectroscopy

2020-11-10T23:39:36Z

JimL:

Imaging Spectroscopy

2020-11-10T23:38:50Z

JimL: Created page with "In imaging spectroscopy, a photograph is taken in a way that measures the intensity of light at a number of different wavelengths. This process generates a separate light spe..."

Radiation shielding

2020-08-09T17:17:21Z

JimL: /* Protection during transit to Mars */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|Ix
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed ''(TBC)''
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man-made electromagnetic field which deflects ionized particles in a similar manner to the Earth's magnetic field. Several different types of active shield have been proposed, including electric field, magnetic field, and plasma shield designs. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

===Design concepts===

====Protection during transit to Mars====
A straightforward approach to designing an active shield would be to surround the protected space with a spherical enclosure made of a conducting metal that is held at a positive electric charge. Cosmic radiation and solar radiation both consist of positively charged particles, which would be repelled by the positively charged shield.

One drawback to this concept is that the shield would attract free electrons and accelerate them, creating secondary radiation when they impact the shield. These electrons would also drain the shield's positive charge, increasing the power needed to maintain it.

This led to the idea of adding a negatively-charged outer shield to keep electrons away from the positively-charged inner shield. However, this introduces its own problems: the mass requirement increases substantially, and the two shields must be tightly fixed in precise concentric positions, because any asymmetry would result in a strong attractive force that would pull the two shields together.

More recent concepts have moved away from the idea of enclosing the protected space in a charged shell. A 2006 paper described a design in which trusses extended out from a spacecraft in the x, y, and z directions. The trusses are used to suspend individual sphere-shaped charge centers: positive charges are held 50 m from the spacecraft, and negative charges are 160 m out. These charges are meant to generate an electric field sufficient to deflect incoming ions approaching from any direction. Despite the elimination of the enclosing shells, the authors concluded that the mass requirement was still too high for this design to be practical.<ref>Smith JG, Smith T, Williams M, Youngquist R, and Mendell W. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield. NASA/TM—2006–214302. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20060013423</nowiki></ref>

In 2011, a concept using toroidal (doughnut-shaped) rings as charge centers was studied. Three conductive rings, each with a 45 m radius, are positioned with their axes of symmetry along the x, y, and z axes, and held at a positive voltage. In addition, six negatively-charged spheres are suspended from trusses, 160 m out. For comparison, the researchers ran simulations of this design and a similar design that used only spherical charge centers. Both designs offered good protection from SPE. The toroid design was more effective against GCR. Ring thicknesses of 1, 5, and 10 m were simulated, showing effectiveness against GCR increasing as a function of thickness. To minimize the mass of the shield, the use of an electrostatically inflated membrane structure was proposed for the charge centers: instead of using a rigid metal, the charge center surfaces would be made of a flexible membrane with a conductive coating. Unlike a balloon that is inflated by filling it with a gas, this type of structure would inflate to its intended shape when electrically charged because of repulsion between like charges distributed across the membrane.<ref>Tripathi RK. 2016. ''Meeting the Grand Challenge of Protecting Astronauts Health: Electrostatic Active Space Radiation Shielding for Deep Space Missions''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010094</nowiki></ref>

A 2012 paper by Westover et al. described a design that used a magnetic field. The field could be generated by multiple layers of superconducting material wrapped around a cylindrical spacecraft in double-helix-shaped coils. Their simulations of this design found that a large, weak field was easier to generate than a small, intense field of equivalent shielding effectiveness. They also examined another design, a cylindrical spaceship surrounded by six exterior solenoids, each centered on a separate central axis (unlike the double helix design, in which the magnetic coil and the spacecraft are co-axial). To reduce the magnetic field inside the spacecraft, a compensation coil, with a current moving in the opposite direction, would surround it. Overall this design was judged to be preferable to the double helix design. Shortcomings of the latter design include the fact that the multiple layers of coils make it difficult to design a shield that can be compacted for launch and later expanded in space. In addition, it would be more difficult to block the magnetic field intruding into the spacecraft because the field strength varies more at different points within the spacecraft; problems might also arise from forces created by the magnetic field acting on the shield or spacecraft.<ref>Westover SC, Meinke RB, BurgerWJ, Van Sciver S, Washburn S, et al. 2012. Magnet Architectures and Active Radiation Shielding Study. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20190002579</nowiki></ref>

==Risk-mitigating behavior==
The possible sources of radiation on Mars are man-made sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.

Possible behavioral choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or man-made objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events (SPE). These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in radon because it seems to be low in [[Thorium]] and, by analogy, Uranium as well. However, the habitats are totally enclosed spaces and radon generated by radioactive decay of naturally occurring uranium in the soil might accumulate. As 1 to 3 mSv on Earth comes from atmospheric radon<ref>http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm</ref>, this part of the yearly load might go away, just as it might need to be mitigated if radon accumulates in the enclosed habitats.
*Even just 1/2 to 1 inches of glass reduces radiation dosage significantly.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Radiation shielding

2020-07-26T17:07:12Z

JimL: /* Active shielding */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|Ix
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed ''(TBC)''
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man-made electromagnetic field which deflects ionized particles in a similar manner to the Earth's magnetic field. Several different types of active shield have been proposed, including electric field, magnetic field, and plasma shield designs. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

===Design concepts===

====Protection during transit to Mars====
A straightforward approach to designing an active shield would be to surround the protected space with a spherical enclosure made of a conducting metal that is held at a positive electric charge. Cosmic radiation and solar radiation both consist of positively charged particles, which would be repelled by the positively charged shield.

One drawback to this concept is that the shield would attract free electrons and accelerate them, creating secondary radiation when they impact the shield. These electrons would also drain the shield's positive charge, increasing the power needed to maintain it.

This led to the idea of adding a negatively-charged outer shield to keep electrons away from the positively-charged inner shield. However, this introduces its own problems: the mass requirement increases substantially, and the two shields must be tightly fixed in precise concentric positions, because any asymmetry would result in a strong attractive force that would pull the two shields together.

More recent concepts have moved away from the idea of enclosing the protected space in a charged shell. A 2006 paper described a design in which trusses extended out from a spacecraft in the x, y, and z directions. The trusses are used to suspend individual sphere-shaped charge centers: positive charges are held 50 m from the spacecraft, and negative charges are 160 m out. These charges are meant to generate an electric field sufficient to deflect incoming ions approaching from any direction. Despite the elimination of the enclosing shells, the authors concluded that the mass requirement was still too high for this design to be practical.<ref>Smith JG, Smith T, Williams M, Youngquist R, and Mendell W. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield. NASA/TM—2006–214302. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20060013423</nowiki></ref>

In 2011, a concept using toroidal (doughnut-shaped) rings as charge centers was studied. Three conductive rings, each with a 45 m radius, are positioned with their axes of symmetry along the x, y, and z axes, and held at a positive voltage. In addition, six negatively-charged spheres are suspended from trusses, 160 m out. For comparison, the researchers ran simulations of this design and a similar design that used only spherical charge centers. Both designs offered good protection from SPE. The toroid design was more effective against GCR. Ring thicknesses of 1, 5, and 10 m were simulated, showing effectiveness against GCR increasing as a function of thickness. To minimize the mass of the shield, the use of an electrostatically inflated membrane structure was proposed for the charge centers: instead of using a rigid metal, the charge center surfaces would be made of a flexible membrane with a conductive coating. Unlike a balloon that is inflated by filling it with a gas, this type of structure would inflate to its intended shape when electrically charged because of repulsion between like charges distributed across the membrane.<ref>Tripathi RK. 2016. ''Meeting the Grand Challenge of Protecting Astronauts Health: Electrostatic Active Space Radiation Shielding for Deep Space Missions''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010094</nowiki></ref>

A 2012 paper by Westover et al. described a design that used a magnetic field. The field would be generated by coils of superconducting material wrapped around a cylindrical spacecraft. Their simulations found that a large, weak field was easier to generate than a small, intense field of equivalent shielding effectiveness.<ref>Westover SC, Meinke RB, BurgerWJ, Van Sciver S, Washburn S, et al. 2012. Magnet Architectures and Active Radiation Shielding Study. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20190002579</nowiki></ref>

==Risk-mitigating behavior==
The possible sources of radiation on Mars are man-made sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.

Possible behavioral choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or man-made objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events (SPE). These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in radon because it seems to be low in [[Thorium]] and, by analogy, Uranium as well. However, the habitats are totally enclosed spaces and radon generated by radioactive decay of naturally occurring uranium in the soil might accumulate. As 1 to 3 mSv on Earth comes from atmospheric radon<ref>http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm</ref>, this part of the yearly load might go away, just as it might need to be mitigated if radon accumulates in the enclosed habitats.
*Even just 1/2 to 1 inches of glass reduces radiation dosage significantly.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Radiation shielding

2020-07-26T17:04:49Z

JimL: /* Protection during transit to Mars */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|Ix
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed ''(TBC)''
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man made electromagnetic field which deflects ionized particles in the same manner as the Earth's. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

===Design concepts===

====Protection during transit to Mars====
A straightforward approach to designing an active shield would be to surround the protected space with a spherical enclosure made of a conducting metal that is held at a positive electric charge. Cosmic radiation and solar radiation both consist of positively charged particles, which would be repelled by the positively charged shield.

One drawback to this concept is that the shield would attract free electrons and accelerate them, creating secondary radiation when they impact the shield. These electrons would also drain the shield's positive charge, increasing the power needed to maintain it.

This led to the idea of adding a negatively-charged outer shield to keep electrons away from the positively-charged inner shield. However, this introduces its own problems: the mass requirement increases substantially, and the two shields must be tightly fixed in precise concentric positions, because any asymmetry would result in a strong attractive force that would pull the two shields together.

More recent concepts have moved away from the idea of enclosing the protected space in a charged shell. A 2006 paper described a design in which trusses extended out from a spacecraft in the x, y, and z directions. The trusses are used to suspend individual sphere-shaped charge centers: positive charges are held 50 m from the spacecraft, and negative charges are 160 m out. These charges are meant to generate an electric field sufficient to deflect incoming ions approaching from any direction. Despite the elimination of the enclosing shells, the authors concluded that the mass requirement was still too high for this design to be practical.<ref>Smith JG, Smith T, Williams M, Youngquist R, and Mendell W. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield. NASA/TM—2006–214302. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20060013423</nowiki></ref>

In 2011, a concept using toroidal (doughnut-shaped) rings as charge centers was studied. Three conductive rings, each with a 45 m radius, are positioned with their axes of symmetry along the x, y, and z axes, and held at a positive voltage. In addition, six negatively-charged spheres are suspended from trusses, 160 m out. For comparison, the researchers ran simulations of this design and a similar design that used only spherical charge centers. Both designs offered good protection from SPE. The toroid design was more effective against GCR. Ring thicknesses of 1, 5, and 10 m were simulated, showing effectiveness against GCR increasing as a function of thickness. To minimize the mass of the shield, the use of an electrostatically inflated membrane structure was proposed for the charge centers: instead of using a rigid metal, the charge center surfaces would be made of a flexible membrane with a conductive coating. Unlike a balloon that is inflated by filling it with a gas, this type of structure would inflate to its intended shape when electrically charged because of repulsion between like charges distributed across the membrane.<ref>Tripathi RK. 2016. ''Meeting the Grand Challenge of Protecting Astronauts Health: Electrostatic Active Space Radiation Shielding for Deep Space Missions''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010094</nowiki></ref>

A 2012 paper by Westover et al. described a design that used a magnetic field. The field would be generated by coils of superconducting material wrapped around a cylindrical spacecraft. Their simulations found that a large, weak field was easier to generate than a small, intense field of equivalent shielding effectiveness.<ref>Westover SC, Meinke RB, BurgerWJ, Van Sciver S, Washburn S, et al. 2012. Magnet Architectures and Active Radiation Shielding Study. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20190002579</nowiki></ref>

==Risk-mitigating behavior==
The possible sources of radiation on Mars are man-made sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.

Possible behavioral choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or man-made objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events (SPE). These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in radon because it seems to be low in [[Thorium]] and, by analogy, Uranium as well. However, the habitats are totally enclosed spaces and radon generated by radioactive decay of naturally occurring uranium in the soil might accumulate. As 1 to 3 mSv on Earth comes from atmospheric radon<ref>http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm</ref>, this part of the yearly load might go away, just as it might need to be mitigated if radon accumulates in the enclosed habitats.
*Even just 1/2 to 1 inches of glass reduces radiation dosage significantly.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Radiation shielding

2020-07-05T16:40:34Z

JimL: /* Protection during transit to Mars */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|Ix
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed ''(TBC)''
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man made electromagnetic field which deflects ionized particles in the same manner as the Earth's. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

===Design concepts===

====Protection during transit to Mars====
A straightforward approach to designing an active shield would be to surround the protected space with a spherical enclosure made of a conducting metal that is held at a positive electric charge. Cosmic radiation and solar radiation both consist of positively charged particles, which would be repelled by the positively charged shield.

One drawback to this concept is that the shield would attract free electrons and accelerate them, creating secondary radiation when they impact the shield. These electrons would also drain the shield's positive charge, increasing the power needed to maintain it.

This led to the idea of adding a negatively-charged outer shield to keep electrons away from the positively-charged inner shield. However, this introduces its own problems: the mass requirement increases substantially, and the two shields must be tightly fixed in precise concentric positions, because any asymmetry would result in a strong attractive force that would pull the two shields together.

More recent concepts have moved away from the idea of enclosing the protected space in a charged shell. A 2006 paper described a design in which trusses extended out from a spacecraft in the x, y, and z directions. The trusses are used to suspend individual sphere-shaped charge centers: positive charges are held 50 m from the spacecraft, and negative charges are 160 m out. These charges are meant to generate an electric field sufficient to deflect incoming ions approaching from any direction. Despite the elimination of the enclosing shells, the authors concluded that the mass requirement was still too high for this design to be practical.<ref>Smith JG, Smith T, Williams M, Youngquist R, and Mendell W. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield. NASA/TM—2006–214302. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20060013423</nowiki></ref>

In 2011, a concept using toroidal (doughnut-shaped) rings as charge centers was studied. Three conductive rings, each with a 45 m radius, are positioned with their axes of symmetry along the x, y, and z axes, and held at a positive voltage. In addition, six negatively-charged spheres are suspended from trusses, 160 m out. For comparison, the researchers ran simulations of this design and a similar design that used only spherical charge centers. Both designs offered good protection from SPE. The toroid design was more effective against GCR. Ring thicknesses of 1, 5, and 10 m were simulated, showing effectiveness against GCR increasing as a function of thickness. To minimize the mass of the shield, the use of an electrostatically inflated membrane structure was proposed for the charge centers: instead of using a rigid metal, the charge center surfaces would be made of a flexible membrane with a conductive coating. Unlike a balloon that is inflated by filling it with a gas, this type of structure would inflate to its intended shape when electrically charged because of repulsion between like charges distributed across the membrane.<ref>Tripathi RK. 2016. ''Meeting the Grand Challenge of Protecting Astronauts Health: Electrostatic Active Space Radiation Shielding for Deep Space Missions''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010094</nowiki></ref>

==Risk-mitigating behavior==
The possible sources of radiation on Mars are man-made sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.

Possible behavioral choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or man-made objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events (SPE). These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in radon because it seems to be low in [[Thorium]] and, by analogy, Uranium as well. However, the habitats are totally enclosed spaces and radon generated by radioactive decay of naturally occurring uranium in the soil might accumulate. As 1 to 3 mSv on Earth comes from atmospheric radon<ref>http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm</ref>, this part of the yearly load might go away, just as it might need to be mitigated if radon accumulates in the enclosed habitats.
*Even just 1/2 to 1 inches of glass reduces radiation dosage significantly.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Radiation shielding

2020-06-21T17:08:45Z

JimL: /* Active shielding */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|Ix
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed ''(TBC)''
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man made electromagnetic field which deflects ionized particles in the same manner as the Earth's. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

===Design concepts===

====Protection during transit to Mars====
A straightforward approach to designing an active shield would be to surround the protected space with a spherical enclosure made of a conducting metal that is held at a positive electric charge. Cosmic radiation and solar radiation both consist of positively charged particles, which would be repelled by the positively charged shield.

One drawback to this concept is that the shield would attract free electrons and accelerate them, creating secondary radiation when they impact the shield. These electrons would also drain the shield's positive charge, increasing the power needed to maintain it.

This led to the idea of adding a negatively-charged outer shield to keep electrons away from the positively-charged inner shield. However, this introduces its own problems: the mass requirement increases substantially, and the two shields must be tightly fixed in precise concentric positions, because any asymmetry would result in a strong attractive force that would pull the two shields together.

More recent concepts have moved away from the idea of enclosing the protected space in a charged shell. A 2006 paper described a design in which trusses extended out from a spacecraft in the x, y, and z directions. The trusses are used to suspend individual sphere-shaped charge centers: positive charges are held 50 m from the spacecraft, and negative charges are 160 m out. These charges are meant to generate an electric field sufficient to deflect incoming ions approaching from any direction. Despite the elimination of the enclosing shells, the authors concluded that the mass requirement was still too high for this design to be practical.<ref>Smith JG, Smith T, Williams M, Youngquist R, and Mendell W. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield. NASA/TM—2006–214302. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20060013423</nowiki></ref>

In 2011, a concept using toroidal (doughnut-shaped) rings as charge centers was studied. Three conductive rings, each with a 45 m radius, are positioned with their axes of symmetry along the x, y, and z axes, and held at a positive voltage. In addition, six negatively-charged spheres are suspended from trusses, 160 m out. This design appeared to block harmful GCR particles more completely than a comparable design that used individual spherical charges instead of toroids.<ref>Tripathi RK. 2016. ''Meeting the Grand Challenge of Protecting Astronauts Health: Electrostatic Active Space Radiation Shielding for Deep Space Missions''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010094</nowiki></ref>

==Risk-mitigating behavior==
The possible sources of radiation on Mars are man-made sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.

Possible behavioral choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or man-made objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events (SPE). These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in radon because it seems to be low in [[Thorium]] and, by analogy, Uranium as well. However, the habitats are totally enclosed spaces and radon generated by radioactive decay of naturally occurring uranium in the soil might accumulate. As 1 to 3 mSv on Earth comes from atmospheric radon<ref>http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm</ref>, this part of the yearly load might go away, just as it might need to be mitigated if radon accumulates in the enclosed habitats.
*Even just 1/2 to 1 inches of glass reduces radiation dosage significantly.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Radiation shielding

2020-06-07T17:13:06Z

JimL: /* Active shielding */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|Ix
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed ''(TBC)''
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the literature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man made electromagnetic field which deflects ionized particles in the same manner as the Earth's. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

=== Design concepts ===

==== Protection during transit to Mars ====
A straightforward approach to designing an active shield would be to surround the protected space with a spherical enclosure made of a conducting metal that is held at a positive electric charge. Cosmic radiation and solar radiation both consist of positively charged particles, which would be repelled by the positively charged shield.

One drawback to this concept is that the shield would attract free electrons and accelerate them, creating secondary radiation when they impact the shield. These electrons would also drain the shield's positive charge, increasing the power needed to maintain it.

This led to the idea of adding a negatively-charged outer shield to keep electrons away from the positively-charged inner shield. However, this introduces its own problems: the mass requirement increases substantially, and the two shields must be tightly fixed in precise concentric positions, because any asymmetry would result in a strong attractive force that would pull the two shields together.<ref>Smith JG, Smith T, Williams M, Youngquist R, and Mendell W. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield. NASA/TM—2006–214302. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20060013423</nowiki></ref>

Recently studied concepts have moved away from spherical enclosures to consider point-like or toroidal (doughnut-shaped) charge centers, which require less mass. The goal is to arrange these charges in a way that generates an electric field sufficient to deflect incoming particles approaching from any direction.

==Risk-mitigating behavior==
The possible sources of radiation on Mars are man-made sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occurring [[radioactive elements]] on Mars.

Possible behavioral choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or man-made objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events (SPE). These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in radon because it seems to be low in [[Thorium]] and, by analogy, Uranium as well. However, the habitats are totally enclosed spaces and radon generated by radioactive decay of naturally occurring uranium in the soil might accumulate. As 1 to 3 mSv on Earth comes from atmospheric radon<ref>http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm</ref>, this part of the yearly load might go away, just as it might need to be mitigated if radon accumulates in the enclosed habitats.
*Even just 1/2 to 1 inches of glass reduces radiation dosage significantly.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Radiation shielding

2020-05-12T22:14:25Z

JimL: /* Possible Shielding Materials */

[[Image:WaterShieldGreenhouse.png|thumb|right|300px|Water-shield Greenhouse Concept]]
Shielding against [[radiation]] is considered a very difficult task. For example, a proton or alpha particle cosmic ray of "medium" energy can pass through more than a meter of aluminium, not counting the effects of [[secondary radiation]]<ref name="Logan">''Operational medicine and health care delivery'' - J.S. Logan, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 154-156.</ref>. With this in mind, it is clear that any Martian colonists would have to take a holistic approach, reducing their radiation exposure at every possible opportunity through shielding and risk-mitigating behaviour.

==Passive shielding==
[[Image:Greenhouse_marsfoundation.jpg|thumb|left|300px|The [[Mars Foundation]] concept for a side-lit greenhouse.]]
In most cases, matter placed between a person (or radiation-sensitive equipment) and radiation source reduces the amount of radiation they absorb.

[[Mars One]]'s solution is a thick layer of [[regolith]] on top of the settlement modules. An effective shield will require at least several hundred grams of regolith per square centimeter, according to one study.<ref>Slaba, T. C., Mertens, C. J., & Blattnig, S. R. (2013). Radiation Shielding Optimization on Mars. ''NASA/TP–2013-217983.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456.pdf</ref> Using a regolith density estimate of 1.4 g/cm3<ref name=":1">Kim, M. Y., Thibeault, S. A., Simonsen, L. C., & Wilson, J. W. Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays. ''NASA TP-1998-208724.'' Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237030.pdf.</ref>, this means the regolith layer would need to be over 2 meters deep. For concrete with an average density of 2.4 g/cm3 the required thickness might be less.
 
 
 
===Protection from Electromagnetic Radiation===
The attenuation of radiation follows the Beer Lamberth law.<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref>

Ix=Io*e-ux
{| class="wikitable"
|Where:
|I
|=
|the intensity of photons transmitted across some distance x
|-
|
|I0
|=
|the initial intensity of photons (or radiation in general)
|-
|
|s
|=
|a proportionality constant that reflects the total probability of a photon being scattered or absorbed
|-
|
|µ
|=
|the linear attenuation coefficient
|-
|
|x
|=
|distance traveled (thickness of material)
|}
{| class="wikitable"
|+Linear Attenuation Coefficients (in cm-1) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0">https://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/Attenuation_of_Gamma-Rays</ref>
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|0.000195
|0.000159
|0.000112
|-
|'''Water'''
|0.167
|0.136
|0.097
|-
|'''Carbon'''
|0.335
|0.274
|0.196
|-
|'''Aluminium'''
|0.435
|0.324
|0.227
|-
|'''Iron'''
|2.72
|1.09
|0.655
|-
|'''Copper'''
|3.8
|1.309
|0.73
|-
|'''Lead'''
|59.7
|10.15
|1.64
|}

the linear attenuation coefficient µ is not commonly found in the litterature, the mass attenuation coefficient µm is usually used instead. The coefficient is also dependent on the type of radiation, so a complete solution for radiation protection requires multiple analysis of the type of radiation to be protected against.

Conversion is quite simple as:

µ=µm*density of the material

List of mass attenuation coefficients<ref>https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/attenuationCoef.htm</ref> can be found at the NIST website. https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html

Another common way of evaluating radiation shielding is to use the '''half value,''' that expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two, or Ix=Io / 2.

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:
{| class="wikitable"
|+Half Value Layers (in cm) for a range of materials at gamma-ray energies of 100, 200 and 500 keV.<ref name=":0" />
!Absorber
!100 keV
!200 keV
!500 keV
|-
|'''Air'''
|3555
|4359
|6189
|-
|'''Water'''
|4.15
|5.1
|7.15
|-
|'''Carbon'''
|2.07
|2.53
|3.54
|-
|'''Aluminium'''
|1.59
|2.14
|3.05
|-
|'''Iron'''
|0.26
|0.64
|1.06
|-
|'''Copper'''
|0.18
|0.53
|0.95
|-
|'''Lead'''
|0.012
|0.068
|0.42
|}
The first point to note is that the Half Value Layer decreases as the atomic number increases. For example, the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The Half Value Layer increases with increasing gamma-ray energy. For example, from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV.

===Protection from Particulate Radiation===
On Earth, particulate radiation is often easily addressed because the particles have low enough energies that they can be stopped by a thin shield. In space and on the surface of Mars, shielding needs to account for high-energy particles. When it comes to particulate radiation, the effectiveness of shielding increases with the mass of the shielding and decreases with the atomic mass of the elements used for the shielding. The reason that low-atomic-mass elements are advantageous is that they generate less secondary radiation when impacted by particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M, Shinn JL, Badavi FF. Radiation Shielding Design Issues. In *Shielding Strategies for Human Space Exploration* (Chapter 7). <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref> For example, 1kg of [[hydrogen]] offers more protection then 1kg of [[aluminium]], 2kg of aluminium offers more protection than 1kg of aluminium and 1kg of hydrogen offers more protection than 2kg of aluminium.<ref>''Radiation biology'' - J.R. Letaw, in S.E. Churchill ed. ''Fundamentals of space life sciences, Volume 1'' - 1997, ISBN 0-89464-051-8 pp. 16-17.</ref> Also, particles interact with atomic nuclei, while electromagnetic radiation interacts with electrons. So while for electromagnetic radiations the effectiveness of shielding increases with the number of electrons, and therefore with heavier atoms that have more electrons, for particles the effectiveness of radiation protection increases with the number of nuclei per volume, and lighter materials such as hydrogen have more nuclei per volume.

===Possible Shielding Materials===
{| class="wikitable"
|+Comparison of Material Options
!Material
!Advantages
!Disadvantages
|-
|Metal
|Efficiency of using structural material for incidental shielding benefit; some metals block EM radiation very well
|Secondary radiation<ref name=":2">Parker LJ. (2016). Human radiation exposure tolerance and expected exposure during colonization of the Moon and Mars. <nowiki>http://www.marspapers.org/paper/Parker_2016_1.pdf</nowiki></ref>
|-
|Plastic
|High hydrogen content<ref name=":2" />
|Less structural utility than metal
|-
|Water
|High hydrogen content<ref name=":2" />
|Liquid
|-
|Liquid hydrogen
|Pure hydrogen
|Cryogenic liquid
|-
|Regolith
|Obtainable through ISRU
|Large thickness required for thorough shielding<ref>James G, Chamitoff G, and Barker D. Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. <nowiki>http://hdl.handle.net/2060/19980147990</nowiki></ref>
|-
|Regolith plus epoxy
|Mostly obtainable through ISRU; greater hydrogen content than regolith alone; more durable and easier to shape than regolith alone<ref name=":1" />
|More complex to implement than regolith alone
|-
|Boron nitride nanotubes
|Low atomic numbers; boron absorbs secondary neutrons well compared to other elements; possible use as both shielding and structural material<ref>Tiano, Amanda L, et al. “Boron Nitride Nanotube: Synthesis and Applications.” NTRS Document ID 20140004051, 2014. <nowiki>http://hdl.handle.net/2060/20140004051</nowiki></ref>; hydrogen could be stored in or bonded to nanotubes to improve shielding<ref>Thibeault SA, Fay CC, Lowther SE, Earle KD, Sauti G, Kang JH, Park C, McMullen AM. (2012). ''Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I''. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20160010096</nowiki></ref>
|Difficult to manufacture
|}

==Active shielding==
Active shielding against radiation involves a man made magnetic field which deflects ionized particles in the same manner as the Earth's. Such fields might require infeasible amounts of energy to generate and could also pose a major risk to anyone approaching the craft or base, as it would create bands of trapped particles similar to the Van Allen belts.<ref name="Logan" /> However, the radiation exposure might be low, as traversing the magnetic shield should be a very brief event.

It might be possible to situate a base in such a location that one of the residual Martian magnetic fields offers a net benefit. Care should certainly be taken not to situate it where the fields concentrate radiation.

Also, it might be possible (assuming one could generate the required magnetic field in some way) to have the radiation belts of the habitat pass through some sort of physical barrier, which scrubs them of particles.

==Risk-mitigating behaviour==
The possible sources of radiation on Mars are manmade sources, such as nuclear reactors or medical equipment, [[solar radiation]], [[galactic cosmic radiation]] and naturally occuring [[radioactive elements]] on Mars.

Possible behavioural choices which minimize the risk from these include:

*Avoiding daytime [[EVA]] when there is a significant risk from solar radiation.
*Working preferentially close to natural or manmade objects, such as habitats, rovers or cliffs which provide additional (if not omni-directional) shielding.
*Entering a [[storm shelter]] when there is a high-radiation risk from [[solar particle event|solar particle events]].

==Example of using shielding and behavior to reduce radiation dosage==
We can combine passive shielding with risk mitigating behavior to achieve low radiation exposure but still allow for some views of the exterior through windows. For example:

*Martian background average radiation is 240-300 mSv per year<ref>NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig ''Radiation Shielding Optimization on Mars'' , <nowiki>https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf</nowiki>, Apr 2013.</ref>.
*If you sleep in a radiation shielded space such as underground rooms with a thick regolith cover, 8/24 hours, then the dose would go down by 1/3, to 160-200 mSv per year.
*If you spend most of your living (work, study) time in a radiation shielded space, then your dose becomes another 1/3 less, or 80 to 100 mSv.
*With overhangs and a radiation proof roof, 70% of the incident radiation to a space close to windows can be stopped by geometries, then the dose is down to 20 to 25 mSv. this is about the 20 mSv per year for a 5 year period that is recommended for radiation workers.
*Part of the surface dose on Mars is solar proton events. These are predictable and detectable, and a large settlement will mostly be built of shielded areas. So during Solar Proton Events you should stay away from the windows. This behavior might reduce the yearly radiation load another 25%, down to 15-18 mSv per year.
*What is the portion of the dosage from SPE? I have a weak reference that puts this at 30%. If correct, then the radiation load from large windows under a radiation proof ceiling is acceptable.
*Mars should be low in Radon because it is low in Thorium, and any thorium in the atmosphere can be separated out when the habitat atmosphere is produced. As 2 mSv on Earth comes from atmospheric radon, then this part of the yearly dose goes away.
*Even just 1/2 to 1 inches of glass reduces radiation dosage.

If the above is correct, then large windows are not really an issue. Geodesic glass domes over public spaces might be a poor choice, unless there is an understanding that you don't spend more than 2 to 4 hours per day under them.

==References==

<references />

[[Category:Radiation Protection]]

Geological processes that have shaped Mars: Why Mars looks like it does

2020-05-07T19:40:30Z

JimL: Made a few minor format changes which I think improve alignment of images.

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:Mars, Earth size comparison.jpg|left|thumb|px|Earth and Mars Earth is much bigger, but both have the same land area. Mars has about one third the gravity of the Earth.]]

Mars looks like it does because of certain geological processes. Some of them are common to both the Earth and Mars. However, others are rare or nonexistent on the Earth. Mars shows an extremely old record of the past that is lacking on the Earth. Plate tectonics and vigorous air and water erosion has wiped out nearly all of the past geology of the Earth. In contrast, much of the Martian surface is billions of years old. Another factor that has affected the appearance of Mars is its extreme cold. The coldness of the planet makes carbon dioxide significant. It has influenced Mars both as a gas and as a solid. As a greenhouse gas, early in the history of the planet, it may have been thick enough in the atmosphere to help raise the temperature enough to permit water to flow, to carve rivers, to form lakes and an ocean. Indeed, it may have been warm enough from carbon dioxide for life to first originate on Mars and then travel to the Earth on meteorites. Today, as a solid, carbon dioxide (dry ice) produces the ubiquitous gullies found in numerous areas of the planet.

==Erosion Related==

As on the Earth material was laid down and then later eroded. Many spectacular scenes are present with places that were mostly eroded, but with remnants remaining in the form of buttes and mesas. Sometimes, sediments were put down in layers. As a result beautiful places were created. On the Earth we admire such layers in Monument Valley and many beautiful canyons. The same types of landscapes show up on Mars.
The top layer of buttes and mesas is hard and resistant to erosion. It protects the lower layers from being eroded away. On Mars that hard, cap rock could be made from a lava flow. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area.

<gallery class="center" widths="380px" heights="360px">

File:16 21 2117 monument valley.jpg|Spearhead Mesa in Monument Valley Note the flat top and steep walls that are characteristic of mesas.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it.

File:58563 2225mesa.jpg|Mesa

File:45016 2080mesas.jpg|Mesas, as seen by HiRISE under HiWish program These are like the ones in Monument Valley

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte: Buttes have a much smaller area than mesas, but both have a hard cap rock on the top. Box shows the size of a football field.

</gallery>

As on the Earth, there are landslides. However, they could be a little different since Mars has only about a third of Earth’s gravity.

<gallery class="center" widths="380px" heights="360px">

File:ESP 043963 1550landslide.jpg|Landslide

</gallery>

Common features in certain areas of the Earth’s surface are “Yardangs.” They are found in desert areas which contain much sand. The wind blows sand and shapes the relatively soft grained deposits into the long, boat shapes of yardangs. On Mars it is thought that these forms are the result of the weathering of huge ash deposits from volcanoes. Mars has the biggest known volcanoes in the solar system. Many probably threw out much fine-grained material which was easily eroded to make vast fields of yardangs. Regions called the “Medusa Fossae Formation and Electris deposits contain thousands of yardangs.

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs.jpg|Yardangs
</gallery>

Unlike the Earth, Mars shows landscapes that are billions of years old. In that time material has been deposited and then eroded and/or greatly changed. Some features have been “inverted.” Low areas turned into high areas. Low areas like stream beds were filled with erosion-resistant materials like lava and large rocks. Later, the surrounding, softer ground became eroded. As a result, the old stream bed now appears raised. We can tell it was originally a stream bed since the overall shape from above still looks like a stream with curves and branches.

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Inverted streams Here a branched stream became filled with hard material and then the surrounding ground was eroded.]]

Another structure made with erosion is a “pedestal crater.” They are abundant in regions far from the equator. These craters seem to sit on little circular shelves or pedestals. In the impacting process, ejecta fell about the crater and protected the underlying ground from erosion. These craters occur where we think there was a great deal of ice in the ground. So, much of the material that disappeared was just ice. With that being said, pedestal craters give us an indication of how much ice was in the region. In some places hundreds of meters of ice-rich ground were removed to make pedestal craters.<ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

[[File:ESP 037528 2350pedestal.jpg |thumb|left|px||Pedestal crater Surface close to crater was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

[[Image:Pedestal crater3.jpg |thumb|right|px||Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings]]

[[File:Pedestaldrawingcolor2.jpg|thumb|600px|center|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

Some structures on Mars are being “exhumed.” Craters are observed that are being uncovered. In the past, impacts produced craters. Later, they were buried. Now they are in the process of being uncovered by erosion. When an asteroid strikes the surface it generates a hole and throws out ejecta all around it. A circular hole is the result. If we see a half of a crater, we know that that it is being exposed by erosion. Impacts do not produce half holes!

<gallery class="center" widths="380px" heights="360px">

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]
</gallery>

==Craters==

Impact craters occur on both the Earth and Mars. However, due to the extreme age of the Martian surface, most of Mars shows a high density of impact craters especially in the southern hemisphere. Craters do not last long on the Earth. Remember, the Earth experiences a great deal more erosion due to its thick atmosphere and abundant water. And, at intervals, the crust is taken into the Earth at plate boundaries. We know a fair amount about impact craters because the Earth has impact craters like Meteor Crater in Arizona that we can study easily.

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File:Barringer Crater USGS.jpg|Meteor Crater in Arizona
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We know that a new crater will have a rim and ejecta around it. Large ones may have a central uplift and maybe a ring around the middle of the floor. We know that the impact brings up material from deep underground.<ref>https://www.uahirise.org/hipod/PSP_007464_1985</ref> If we study the rocks in the central mound and in the ejecta, we can learn about what is deep underground.

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterejectarim.jpg|Young crater showing layers, rim, and ejecta. Ejecta was thrown out by the force of impact.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.
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The heat from an impact into ice-rich ground may produce channels emanating from the edge of the ejecta. These have been seen around a number of craters.

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File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

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Mars shows some interesting variations to the usual appearance of craters. At times the force of an impact reaches down to a different type of layer. The lower layer may be of a different color; therefore the ejecta that is spread on the landscape may be a different color.

<gallery class="center" widths="380px" heights="360px">
File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta Impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:29565 2075newcratercomposite.jpg|New, small crater Meteorite that hit here throw up dark material that was under a layer of bright, surface dust. We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref>

File:ESP 011425 1775newcrater.jpg|Dark ejecta of a new crater covers the bright surroundings.
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Sometimes it looks as if an impact caused rocks to melt and when the molted rocks landed on the crater floor steam explosions occurred with ice-rich ground. What results is ground with a high density of pits.

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File:ESP 012531 1435pits.jpg|Floor of Hale Crater showing pits from steam explosions when hot, melt from an impact landed.

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On occasion, an impact may go down to ice-rich ground or maybe to a layer of ice. Indeed, a number of craters expose ice on their floors which after a period of time disappears into the thin Martian atmosphere.

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File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
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Then there is a type of crater which is common in locations we think contain much ice. Called “ring-mold” craters, they may be caused by a rebound of an ice layer. Experiments in labs confirm that this behavior can occur. Ring-mold craters are called that because they resemble ring-molds used in baking.

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File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.

26055ringmoldcrater.jpg|Close view of ring mold crater.
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[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Now, during the impact process much material is sent flying in the air. Some of it will come down and create new craters. These are called secondary craters. They can be identified by all being of the same age. In addition, sometimes molted rock is produced by the impact. If molten rock lands on ice-rich ground, an area with a high density of pits will form. The hot molten rocks cause ice in the ground to burst into steam and cause pits to form.

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File:ESP 030244 2040secondarycraters.jpg|Secondary craters These are formed from material that is blasted way up in the air from the impact. Evidence that they are secondary craters is that they are all of the same age.
</gallery>

==Glaciers==

Mars may have had much water in past ages. Much of that water is now frozen in the ground and locked up in glacier-like forms. Many features have been found that are like glaciers—in that they are mostly made of ice and flow like glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> That means they move slowly and in a downhill direction. For ice to exist under today’s climate conditions, it must be covered with a layer of debris—dust, rocks, etc. A layer several meters or a few tens of meters thick will preserve ice for millions of years. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> Under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>
Martian glaciers show evidence of movement on their surfaces and in their shapes. The actual existence of water ice in some of them has been proven with radar studies from orbit. <ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> Some of them look just like alpine glaciers on the Earth. Most show piles of debris called moraine. This was material that was removed from one place and moved along to another by ice. Also, shapes looking just like eskers of terrestrial glaciers are common in places. Eskers form from streams moving under glaciers. These streams deposit rocks in tunnels in the ice at the bottom of glaciers. When the ice goes away, curved ridges stay behind.

<gallery class="center" widths="380px" heights="360px">

File:R0502109dorsaargentea.jpg|Possible eskers indicated by arrows. Eskers form under glaciers.

Wikilau.jpg|Lau Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Curved ridges are probably eskers which formed under glaciers.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.

File: Wikielephantglacier.jpg|Glacier in Greenland Glacier spreads out when it leaves valley.
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For Mars, a number of names have been applied to these glacier-like forms. Some of them are tongue-shaped glaciers, lobate debris aprons (LDA’s), lineated valley fill (LVF), and concentric crater fill (CCF).<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 035327 2255tongues.jpg|Tongue-shaped glaciers These were made when a flow encountered an obstacle that made it split into two.
File:ESP 036619 2275ldalabeled.jpg|Lobate debris apron LDA) around a mound <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust . <ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref>

File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are now almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed. <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>
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[[File:ESP 052138 1435lvf.jpg|thumb|600px|center|Lineated valley fill, as seen by HiRISE under [[HiWish program]]]]

==Ice in the ground==

Mars has some unique landscapes and features that are common just to it. Since so much water is frozen in the ground and since the thin atmosphere of Mars allows ground ice to disappear when it became exposed, unreal scenes can develop. Under current conditions on Mars, ice sublimates when exposed to the air. In that process, ice goes directly to a gas instead of first melting. It often starts with small, narrow cracks that get larger and larger. Once ice leaves the ground there is not much left except dust. And winds will eventually carry the dust away. The end result is various shaped holes, pits, canyons, and hollows. Some of these forms are called brain terrain, ribbed terrain, hollows, scalloped terrain, and exposed ice sheets. <ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> All of these may be of use to future colonists who need to find supplies of water.

[[File:45917 2220brainsopenclosed.jpg|Open and closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>]]

Open and closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollow

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain <ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> <ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref>
PIA22078 hireswideview.jpg|Wide view of triangular depression The colored strip shows the part of the image that can be seen in color. The wall at the top of the depression contains pure ice. This wall faces the south pole. <ref>Supplementary Materials Exposed subsurface ice sheets in the Martian mid-latitudes Colin M. Dundas, Ali M. Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, Nathaniel E. Putzig, Donna Viola, Sarah Sutton, Erin Clark, John W. Holt</ref>

PIA22077 hirescloseblue.jpg|Close, color view of wall containing ice from previous image <ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> <ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref>
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[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of hollowed terrain caused by ice leaving the ground Box shows size of football field.]]

Close view of terrain caused by ice leaving the ground Box shows size of football field.

Other signs of water ice in the ground are: lobed (rampart craters), patterned ground, and possible pingos. Pattered ground or polygonal ground is common in ice-rich areas on Earth.

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File:56942 1075icepolygonslabeled2.jpg|Polygons Ice is in the low troughs that lie between the polygons.

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Pingos are mounds that contain a core of ice.<ref>http://www.uahirise.org/ESP_046359_1250</ref> <ref>Soare, E., et al. 2019.</ref> <ref> Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref> They often have cracks on their surfaces. Cracks form when water freezes and expands. Pingos would be useful as sources of water for future colonies on the planet.

<gallery class="center" widths="380px" heights="360px">
51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.
ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program
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Craters with ejecta that look like they were made by an impact into mud are called lobed or rampart craters. They were discovered by early, orbital missions to Mars. They are most common where we expect ice in the ground.

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File:Mars rampart crater.jpg|Yuty Crater showing lobe and rampart morphology; it looks like mud was formed during the impact.

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Channels are sometimes found in a crater's ejecta or along the edges of the ejecta. Heat from the ejecta probably melted ice in the ground. Much heat is produced with an impact.

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File:ESP 055530 2180channels.jpg

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==Liquid water==

Mars used to have lots of water and maybe a much thicker atmosphere billions of years ago. With liquid water, life is possible. Indeed, life may have first appeared on Mars before it occurred on Earth. Martian organisms could have been knocked off Mars by low angle asteroid impacts and found their way to Earth. Perhaps, the DNA of all Earthly organisms, included us, still contains genes from early Martian life. When we have samples of Mars brought back to Earth, we may find traces of DNA that are like ours.
Data are still being gathered and ideas debated, but scientists think that once Mars cooled down and lost its magnetic field, the solar wind may have carried away much of its atmosphere. In addition, some researchers have suggested that some of the atmosphere was splashed out by impacts. After the planet cooled, water became frozen in the polar ice caps and in the ground. But, for some period there was liquid water.

[[File:Mars vs Earth Solar Wind-1024x576.png|Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field]]

Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field

[[File:Mavenargoninfographic2.jpg|This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.]]

This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.

Huge amounts of water had to be present to carve the many outflow channels and produce the valley networks. Many of the outflow channels begin in "Chaos Terrain." Such a landscape often is where the ground seems to have just collapsed into giant blocks.<ref>https://marsed.asu.edu/mep/ice/chaos-terrain</ref> <ref>https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-9213-9_46-2</ref> It is believed that a shell of ice was created when the planet's climate cooled. Perhaps, at times the shell was broken by asteroid impacts, movements of magma, or faults. Such events would allow pressurized water to rapidly escape from under the shell of ice (shell has been called a cryosphere). Evidence is accumulating for the existence of an ocean. Lakes existed in low spots, especially craters.

[[File:ESP 056689 2210channelslowspotcropped.jpg |thumb|right|px||Channels that empty into a low area that could have been a lake Arrows show channels that lead to a low area that could have hosted a lake.]]

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel

These forms were shaped by running water.

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File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.

File:Ravi Vallis.jpg|Ravi Vallis was formed when the ground released a great flood of water from Aromatum Chaos. Maybe it started when hot magma moved under the ground.

File:Ister Chaos.jpg|Ister Chaos Water may have come out of this landscape when the ground broke up into blocks.<ref>https://www.uahirise.org/hipod/PSP_008311_1835</ref>

File:Branched Channels from Viking.jpg|These valley networks look like they were made from precipitation.
</gallery>

At present, it is hotly debated just how long water stayed around. The sun was not as strong billions of years ago. Greenhouse gases like carbon dioxide, methane, and hydrogen may have made Mars warm enough for liquid water. Massive volcanoes would have given up many of these gases, along with water vapor.

[[File: Olympus Mons Side View.svg.png|thumb|left|300px|Height of Olympus Mons compared to tall mountains on Earth]]

Maybe the water just existed for short periods. Some studies have showed that large impacts into icy ground could release water and change the local climate for thousands of years. Also, impacts may have punctured an ice shell and allowed pressurized water to flow out for a time. Any water moving on the surface would quickly freeze at the top. But, it would continue to flow under the ice for a long time and make many of the channels we see today. Heat to allow water to flow may have been from underground flows of magma. On the other hand, many of the features created by liquid water could have formed under massive ice sheets where water was insulated from the Martian atmosphere.
 
==Layers==

Many locations display layered formations. Some are mostly just made of ice and dust. These types of layers are common in the polar ice caps, especially the northern ice cap.<ref>https://www.uahirise.org/hipod/PSP_008244_2645</ref> Other, rockier layers, are visible in the walls of impact craters and canyon walls.

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File:PSP 008244 2645northicecaplabeled.jpg|Layers in northern ice cap that are exposed along a cliff

File:ESP 054515 2595icecaplayers.jpg|Close view of many layers exposed in northern ice cap
File: 57080 1380layerscratercolor.jpg|Layers in crater wall in Phaethontis quadrangle, as seen by HiRISE under HiWish program
48980 1725layersclose2.jpg|Close view of layers in Louros Valles
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And then there are layers that may be more recent, they may be connected to repeated climate changes. Some have regularity to them. The climate of Mars changes drastically due to changes in the tilt of its rotational axis. At times, like now, it is close to the Earth’s 23.5 degrees. But, at times it may be as much as 70 degrees.<ref> Schorghofer, Norbert (2008). "Temperature response of Mars to Milankovitch cycles". Geophysical Research Letters. 35 (18): doi:10.1029/2008GL034954.</ref> <ref>ouma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref>Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Tilt governs the seasons and where ice is distributed. Currently, the largest deposit of ice is at the poles. At other times could have been at mid-latitudes. Imagine how it would be to have Pittsburgh under an ice cap. Mars may have had ice caps at the latitude of Pittsburgh.

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File:Mars Ice Age PIA04933 modest.jpg|How Mars may have looked with a greater tilt of Mars' rotational axis caused increased solar heating at the poles. This larger tilt would make a surface deposit of ice and dust down to about 30 degrees latitude in both hemispheres.
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There is an ice-rich material that falls from the sky. It is called latitude dependent mantle.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It is thought to come from snow and ice-coated dust. At times, there is a lot of dust in the air. When that happens, moisture will freeze onto dust grains. When the ice-coated dust particle gets heavy enough, it will fall. Recent accumulations of this mantle look smooth. In some places the mantle is layered. Some formations, particularly in protected spots in craters and against mounds, suggest that these layered formations had many more layers. The wind sometimes shapes them into layered mounds.

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.
[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

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File:ESP 035801 2210dipping.jpg|Layers leaning against a mound The mound protected them from erosion.
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The older layers visible on crater and canyon walls may have different sources. Some are from lava flows or ash from volcanoes. Some may have formed under water like most layered sedimentary rocks on the Earth.<ref>https://www.uahirise.org/PSP_008391_1790</ref> Curiosity, our robotic explorer, has found that layers in Gale Crater were made from sediments at the bottom of a lake. Some may be just from dust and debris settling in low areas and then being cemented by rising groundwater carrying minerals like sulfates and silica.<ref> Rates and mechanisms of chemical weathering of ferromagnesian silicate minerals on Mars | date = 1993 | last1 = Burns | first1 = Roger G | journal = Geochimica et Cosmochimica Acta | volume = 57 | issue = 19 | pages = 4555–4574 |</ref> <ref>{{cite journal | doi = 10.1029/92JE02055 | title = Rates of Oxidative Weathering on the Surface of Mars | date = 1993 | last1 = Burns | first1 = Roger G. | last2 = Fisher | first2 = Duncan S. | journal = Journal of Geophysical Research | volume = 98 | issue = E2 | pages = 3365–3372 |</ref> <ref>Hurowitz | first1 = J. A. | last2 = Fischer | first2 = W. W. | last3 = Tosca | first3 = N. J. | last4 = Milliken | first4 = R. E. | year = 2010 | title = Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars | url = https://authors.library.caltech.edu/18444/2/ngeo831-s1.pdf| journal = Nat. Geosci. | volume = 3 | issue = 5| pages = 323–326 | doi = 10.1038/ngeo831 | </ref> Sometimes a crater may have been filled up with layered rocks and then the rocks may have been eroded by the wind in such a way to just leave a layered mound in the center of the crater. Gale crater, where Curiosity is exploring, was like that.

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Image:Topographic Map of Gale Crater.jpg|Gale Crater with Aeolis Mons rising from the center. The noted [[Curiosity]] landing area is near Peace Vallis in Aeolis Palus. Curiosity landed in the northern part of the crater. Colors indicate elevation.

File:Marscratermounds.jpg|Some layers form mounds in the center of craters. They could have been made by the erosion of layers that were deposited after the impact.

</gallery>

[[File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|600pxr|Rock layers in the Murray Buttes area in lower Mount Sharp They look like rocks formed at the bottom of lakes and their chemistry proves it.]]

Rock layers in the Murray Buttes area in lower Mount Sharp

==Igneous effects==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

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File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons

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Igneous refers to rock that is heated to a molten condition. On Mars, this is a major shaper of landscapes. Lava comes out of the ground at holes called vents. Flows of lava can be about as fluid as water and move long distances. Sometimes the top cools to a solid, but the liquid rock continues to flow underneath a hard crust. Giant pieces of this stiff crust can move around as “lava rafts.”

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File:ESP 054891 2040lavarafts.jpg|Lava rafts
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In other places, lava travels in channels. When they make a hard crust, lave tunnels are created. A picture below shows lava tunnels.<ref> https://www.uahirise.org/PSP_009501_1755</ref> After the liquid lava moves away, an empty tunnel can be formed. These are significant for future colonists as they may be where our first colonies will be built. There people would be protected from surface radiation. We have already found spots that might be openings to these tunnels in HiRISE images.

[[File:PSP 009501 1755lavatube.jpg |Lava tubes and lava tunnels Future colonists may live in lava tunnels.]]

[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|left|Possible cave entrance to a lava tunnel Future colonies may live in caves for protection from weather and radiation.]]

[[File:Tharsis mons Viking.jpg |right|thumb|px|Some of the Martian volcanoes, as seen by Viking 1]]

There are huge volcanoes that were noticed by our first spacecraft to orbit the planet. The first satellite to orbit the planet was only able to see a few volcanoes peeking above a massive global dust storm. Since Mars has not had plate tectonics for nearly all of its history, volcanoes can grow very large.<ref>https://www.jpl.nasa.gov/edu/learn/video/mars-in-a-minute-how-did-mars-get-such-enormous-mountains/</ref> Lava and ash can erupt from the same spot for long periods of time. On the Earth, the plates move so volcanoes can only grow so big.

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File:Olympus Mons alt.jpg|Olympus Mons, tallest volcano in solar system The mass of volcanoes on mars stretches and cracks the crust causing faults.

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Volcanoes are only the surface manifestations of liquid rock. There is more molted rock moving under the surface than what we see above ground in volcanoes. Molted rock is called magma when underground. Stretching out around volcanoes underground are various structures. Vast linear walls, called dikes radiate out from volcanoes. On Mars they can be many miles in length. Many form by moving along cracks or weak parts of rocks. Some scientists have suggested that they from long troughs when they melt ground ice. Troughs are some of the longest features on Mars.

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File:ESP 045981 2100dike2.jpg|Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

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Besides the direct action of lava and magma, volcanoes affect Mars with just their weight. The mass of a volcano stretches the crust and makes cracks form. The large canyon system of Valles Marineris may have been started with some sort of stretching of the crust. But, its stretching may have been caused by rising mantle plumes or maybe the rise of Tharsis where so many volcanoes are located.<ref>https://astronomy.com/magazine/ask-astro/2013/08/valles-marineris</ref> Cracks in the crust are called faults. Faults on Mars are often double faults. A center section is lower than the sides. This arrangement is called a graben. On the Earth they can turn into lakes like Lake George in New York State. Graben on Mars can be thousands of miles long.

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File:Troughs in Elysium Planitia.jpg|Troughs showing layers Hard cap rock is at the surface. The center section of the picture is in color. With HiRISE only a strip in the middle is in color.

ESP 046251 2165graben.jpg|Straight trough is a fossa that would be classified as a graben. Curved channels may have carried lava/water from the fossa. Picture taken with HiRISE under [[HiWish program]].

File:ESP 057834 2005troughmesa.jpg|Trough or graben cutting through mesa
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Sometimes lava moves over frozen ground. That results in steam explosions. Large fields of small cones can be produced when this happens. Those cones are called “rootless cones” since they do not go down very far.

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File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones
File:45384 2065cones2.jpg|Close view of rootless cones
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Volcanoes sometimes explode with great amounts of ash that travels long distances, covering everything. Some of the layers seen on Mars are probably from these ash deposits. These deposits do not contain boulders and are easily eroded by just the wind. Two areas on Mars have widespread and thick deposits made in this way; they are called the Medusae Fossae Formation and the Electris deposits. These relatively soft deposits often form shapes called yardangs. They are sort of boat shaped and show the direction of the prevailing wind when they were created.

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File:61167 1735yardangs3.jpg|Yardangs
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Much of the atmosphere of Mars came from volcanoes. Volcanoes give off large amounts of carbon dioxide and water, along with other chemicals. Some of these chemical compounds are “greenhouse gases” that served to heat up early Mars.
A few places are thought to be where volcanoes erupted under ice. The shapes that resulted look like those made on Earth when a volcano erupted under the ice.

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

==Bright dust==

A thin coating of bright-toned dust covers almost all parts of Mars. It has a rust brown color. It is not too noticeable until it is not here. Some things remove the dust and then reveal the dark underlying surface. The contrast between this thin coating and the underlying dark rock is striking. Much of the difference derives from how NASA pictures are processed.<ref> Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> To bring out more detail, the brightest tone is considered white, while the darkest black. It only takes a very thin layer of dust to make a difference in the over-all appearance of a picture. Experiments on Earth found that the layer may be only as thick as the diameter of a human hair.<ref> https://en.wikipedia.org/wiki/Micrometre
</ref> Incidentally, the dust has the color of rust because it is rust—it is oxidized iron.

Dark slope streaks occur when bright dust avalanches down steep slopes like crater walls. They can be very long and elaborate. These movements are affected by obstacles like boulders. A streak may split into two when encountering a boulder. They may be initiated when an impact happens nearby.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars" ''Icarus'' 2012; 217 (1) 194 </ref><ref>http://redplanet.asu.edu/</ref>
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>

[[File:ESP 043128 2005mesastreaks.jpg|600pxr|Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]]]

Dark slope streaks on layered mesa

[[File:55107 1930streaksboulders2.jpg|thumb|500px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

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Another thing that causes light and dark patterns is a dust devil. These miniature tornadoes remove the bright dust and make straight and/or curved tracks. They are common especially in areas with much dust cover and at certain times of the day. They have been observed both from orbit and from the ground. We even have movies of them in action. They can form beautiful scenes. And, the arrangement of the tracks can be different in just a few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

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The atmosphere of Mars contains a great deal of fine dust. Large dust storms happen just about every Martian year. A year on Mars is about 23 of our months. Dust storms typically occur when it is spring or summer in the southern hemisphere. At that time, Mars is at its closest to the sun. Unlike the Earth, Mars has a very elliptical orbit which brings it much closer to the sun than at other times. This makes for differences in season both in intensity and length. For example the southern summer is much shorter than that of the north. However, the summer season in the southern hemisphere is much more intense.

[[File:Marsorbitsolarsystem.gif|Comparrsion of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle.<ref> https://www.compadre.org/osp/items/detail.cfm?ID=9757</ref> <ref> https://www.compadre.org/osp/items/detail.cfm?ID=7305</ref>]]

Comparison of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle. Mars changes its distances to sun a great deal--this changes makes drastic seasonal changes.

==Dry Ice==

Some of the strangest things on Mars involve dry ice—solid carbon dioxide. The cold conditions on Mars cause much of the carbon dioxide to freeze out of the atmosphere. Both ice caps contain some dry ice. Each year about 25% of the atmosphere freezes out onto the poles. This is so much that the gravity of the planet shifts. <ref>NASA/Goddard Space Flight Center. "New gravity map gives best view yet inside Mars." ScienceDaily. ScienceDaily, 21 March 2016. https://www.sciencedaily.com/releases/2016/03/160321154013.htm.</ref> <ref>Antonio Genova, Sander Goossens, Frank G. Lemoine, Erwan Mazarico, Gregory A. Neumann, David E. Smith, Maria T. Zuber. Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science. Icarus, 2016; 272: 228 DOI: 10.1016/j.icarus.2016.02.05</ref> Winds and weather systems that almost look like the Earth’s are produced by so much dry ice changing to a gas at these times.

[[File:PIA00190-MC-30-MareAustraleRegion-19980605.jpg |right|thumb|px| Region of South Pole with ice cap Southern ice cap is much smaller than the North’s.]]

[[File:Mars NPArea-PIA00161.jpg |left|thumb|px| Spiral troughs in the northern ice cap]]

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File:Marscyclone hst.jpg|Cyclone on Mars, as seen by HST
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In the winter dry ice accumulates. So, large areas appear white. When things warm up in the spring, the landscape gets many dark spots and areas. <ref>https://mars.jpl.nasa.gov/mgs/msss/camera/images/dune_defrost_6_2001/</ref><ref>SPRING DEFROSTING OF MARTIAN POLAR REGIONS: MARS GLOBAL SURVEYOR MOC AND TES MONITORING OF THE RICHARDSON CRATER DUNE FIELD, 1999–2000. K. S. Edgett, K. D. Supulver, and M. C. Malin, Malin Space Science Systems, P.O. Box 910148, San Diego, CA 92191-0148, USA.</ref> <ref>K.-Michael Aye, K., et al. PROBING THE MARTIAN SOUTH POLAR WINDS BY MAPPING CO2 JET DEPOSITS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2841.pdf</ref> In the past, observers thought that Mars was full of life. They saw the northern ice cap get smaller and smaller. At the same time, they watched the area get darker. They concluded that the darkening was vegetation growing from the water coming out of the ice caps. What was happening was the dry ice was disappearing. Today, we can watch this darkening occur in great detail. <ref>http://www.jpl.nasa.gov/news/news.php?release=2013-034</ref>

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43821 2555defrostingdune2.jpg|Defrosting surface Frost is disappearing in patches from a dune and from the surrounding surface. Note: the north side (side near top) has not defrosted because the sun is coming from the other side.

File:ESP 011605 1170defrosting.jpg|Defrosting The dark spots are where the ice has gone. We now can see the underlying dark surface.

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In some places, there are many geyser-like eruptions of gas and dark dust. High pressure gas and dust explode out of the ground. Winds often blow these eruptions into dark plumes. After many observations, scientists concluded that what happens is that a transparent-translucent dry ice slab forms in the winter. With increased sun in the spring, pressure builds up under this slab as light heats cavities under the slab and causes dry ice to turn into a gas. At weak areas in the slab, the gas comes out along with dark dust.<ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> The channels may get dark from the dust and make a pattern that looks like a spider. These patterns are called “spiders.” <ref>http://mars.jpl.nasa.gov/multimedia/images/2016/possible-development-stages-of-martian-spiders</ref> <ref>http://spaceref.com/mars/growth-of-a-martian-trough-network.html</ref> <ref>Benson, M. 2012. Planetfall: New Solar System Visions</ref> <ref>http://www.astrobio.net/topic/solar-system/mars/spiders-invade-mars/</ref> <ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>Portyankina, G., et al. 2017. Present-day erosion of Martian polar terrain by the seasonal CO2 jets. Icarus: 282, 93-103.</ref> The official name for spiders is "araneiforms."<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

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ESP 048845 1010spiders.jpg|Wide view of crater that contains examples of spiders
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
</gallery>

Around the southern cap, dry ice makes round, low areas that look like Swiss cheese. <ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data
Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> So, it is called “Swiss cheese terrain.” The roundness of the pits is believed to be related to the low angle of the sun.<ref>Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

[[File:South Pole Terrain.jpg|600pxr|HiRISE view of South Pole Terrain.]]
HiRISE view of South Pole Terrain.

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The ice caps contain a great deal of water ice. The northern cap has a covering of dry ice only 1 meter thick in the winter, but the southern cap always has a coating of dry ice up to 8 meters thick. Large deposits of dry ice are also buried in the water ice of the cap at some locations.

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==Gullies==

Since 2000, researchers have been studying gullies that are common in the mid-latitudes on steep slopes. They look like they were carved by liquid water. After many years of observations, it has been concluded that today they are being made by chunks of dry ice sliding down slopes.<ref>Vincendon, M. 2015. JGR:120, 1859–1879.</ref> <ref> Pilorget | first1 = C. | last2 = Forget | first2 = F. | year = 2016 | title = Formation of gullies on Mars by debris flows triggered by CO2 sublimation | url = | journal = Nature Geoscience | volume = 9 | issue = | pages = 65–69 | doi = 10.1038/ngeo2619 | </ref> <ref>Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.</ref> However, some scientists concede that water may have been involved in their formation in the past.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm</ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>

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ESP 047956 1420gullies.jpg|Crater with gullies, as seen by HiRISE under HiWish program
File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
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[[File:Gullies near Newton Crater.jpg|600pxr|Gullies near Newton Crater]]
Gullies near Newton Crater

==Other features==

The surface of Mars is very old—billions of years. This is plenty of time for rocks to have broken down into sand. In low places, like crater floors, sand accumulates and makes dunes. Some are quite pretty. And the colors used by NASA make them even more pretty—they can appear blue, purple, green, or turquoise.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

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File:61974 1710dunesrgb2.jpg|Dunes
File:ESP 046378 1415dunefield.jpg|Black and white, wide view of dunes
File:ESP 55095 2170dunes.jpg|Dunes near Sklodowski Crater in North Arabia Terra
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Related to dunes are something called transverse aeolian ridges (TAR’s). They look like small dunes. They are often parallel to each other. They generally are in low areas and one of the most common landforms on Mars.<ref>http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1598.pdf|format=PDF|type=conference paper|title=Investigations of transverse aeolian ridges on Mars|first1=Daniel C.|last1=Berman|first2=Matthew R.|last2=Balme|year=2012|publisher=Lunar and Planetary Science Conference</ref> They are mid-way in height between dunes and ripples; they are not well understood.<ref>http://www.uahirise.org/ESP_042625_1655</ref> <ref>Berman, D., et al. 2018. High-resolution investigations of Transverse Aeolian Ridges on Mars: Icarus: 312, 247-266.</ref>

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File:ESP 039563 1730tars.jpg|Transverse Aeolian Ridges (TAR’s) between yardangs We do not totally understand these.
File:ESP 042625 1655tars.jpg|Wide view of Transverse Aeolian Ridges (TAR’s) near a channel
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Some landscape expressions are mysteries. There are different ideas for what caused them.
In rocks of certain ages, often at the bottom of low spots are complex arrangements of ridges. These are walls of rock.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>

[[File:ESP 036745 1905top.jpg|600pxr|Linear ridge networks]]

Linear ridge networks

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File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
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Of eerie beauty are odd arrangements visible on the bottom of the Hellas Impact basin. We are not sure exactly what caused them. They have been called honeycomb terrain or banded terrain.

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Honeycomb terrain on floor of Hellas Basin The exact origin of these shapes is unknown at present.

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Mars is one planet that we can see the surface clearly. Its super thin atmosphere (about 1% of the Earth’s) makes it easy to observe. Early telescopes revealed many markings and patterns. As we sent better and better cameras to examine it, more mysteries and more beautiful scenes emerged. We were able to answer many questions, but always more questions arose concerning what we were seeing.

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==References==

{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]

*[https://www.youtube.com/watch?v=jcaawA7d0ro Sublimation of Dry Ice]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

Gravity

2020-05-03T19:27:39Z

JimL: Added to Impact on Humans

[[Mars]] has a mass of 6,419 · 1023 kg. Compared with [[Earth]] this is only a little bit more than a tenth. This results in a lower Gravity as the planet is also less dense than Earth.

The gravitational acceleration is 3,71 m/s², compared to 9,81 m/s2 on Earth. The resulting weight of any body on the surface of Mars is only a bit more than a third, compared with the same body on Earth. Mass and inertia remain the same, however.

==Impact on physics and nature==

*[[Dust storms]] on Mars reach high altitude. Scientists found the cause in the low gravity, allowing the [[sand]] grains to bounce much higher.
*The low gravity and lack of continental drift has allowed the growth of the highest mountain in the [[solar system]], e.g. [[Olympus Mons]].
*A rock thrown on Mars will fly much further than on Earth.

==Impact on humans==
The development of [[children|human embryos]] might be different. Also, the long term consequences for the health of human beings is unclear. Constant [[physical exercise]] has proven to be beneficial on the ISS to reduce calcium loss and maintain muscle mass. However the difference between no gravity and low gravity is still unknown.

The absence of gravity during interplanetary travel could also undermine the fitness of explorers or settlers to perform their jobs upon their arrival at Mars.

=== Potential methods of preventing calcium loss ===
Daily exercise appears to reduce, but not eliminate, calcium loss in a zero-gravity environment. Two hours/day has limited calcium loss to 12%, and 4 hours/day limited it to 5%, during stays on Mir and the International Space Station.

The stress placed on bones by normal gravity causes a certain amount of interstitial fluid flow within bones, which may be important in preserving bone calcium. It might be possible to stimulate this effect using, as a medication, a signaling protein called a growth factor that allows fluid to leak out of blood vessels.

If research identifies a specific gene as the regulator of low-gravity calcium loss, then a more refined version of this approach might be possible. Scientists could attempt to design a medication that targets this specific gene and holds its expression at the same level as it would be in Earth gravity.<ref>McCormack PD. (2005). Chronic health hazards in human space exploration. <nowiki>http://www.marspapers.org/paper/McCormack_2005.pdf</nowiki></ref>

==Impact on technology==

*The pressure on bearings for the same service is lower, causing less friction and abrasion. Or lighter bearings can be used.
*A [[space elevator]] is easier to build.

==Impact on plants==

*Plants have grown normally on the ISS and should grow on Mars. The effect on their internal structure of the low gravity is unknown.

==Impact on Settlement design==
[[File:Icedome Scene 6.jpg|thumb|600x600px]]
For the 2019 Mars Society settlement design contest, Kent Nebergall proposed the [https://macroinvent.com/wp-content/uploads/2019/03/Eureka-Mars-Settlement-Concept.pdf Eureka] base design. This design addresses most of the potential problems that might arise from lower gravity by building the settlement about a pair of rotating ring structures capable of simulating Earth gravity by centripetal force. Usually planned for spaceships, artificial gravity using centripetal force could be implemented on Mars.

The design<ref>https://macroinvent.com/wp-content/uploads/2019/03/Eureka-Mars-Settlement-Concept.pdf</ref> addresses a number of social and technological issues, as well as artificial gravity.
[[File:Icedome gardens.jpg|left|thumb|Cutaway view through the gravity rings]]
[[Category:Gravimetry]]

 
 
 
 
 
 
 
 
 
 
==References==
<references />

Radiation

2020-03-15T18:10:44Z

JimL:

[[Image:nuclear_warning_sign.png|right|Nuclear Danger Icon]]
Natural '''Radiation''' on [[Mars]] is much higher compared with [[Earth]]. The thin [[atmosphere]] provides only a small shielding effect against harmful [[solar radiation]] and [[cosmic radiation]]. Mars also lacks the [[magnetosphere]] that protects Earth.

The average natural radiation level on Mars is 24-30 rads or 240-300 mSv per year(needs checking and reference). This is about 40-50 times the average on Earth.

1 millisievert [mSv] = 0.1 rad [rd]

==Types of Radiation==
Radiation comes in a variety of forms:<ref>http://www.nas.nasa.gov/About/Education/SpaceSettlement/designer/needs.html#SHIELDING</ref>
{| border="1"
|-
!Name
!Relative Biological Effectiveness (RBE)
!Source
|-
|'''[[X-ray|X-Rays]] and [[gamma ray|Gamma Rays]]'''
|1
|[[Radiation belts]], [[solar radiation]], and bremsstrahlung electrons
|-
|'''[[electron|Electrons]]'''
1.0 MeV 
0.1 MeV
| 
1 
1.08
|Radiation belts
|-
|'''[[proton|Protons]]''' 
100 MeV 
1.5 MeV 
0.1 MeV
| 
1-2 
8.5 
10
|[[Cosmic radiation]], inner-radiation belts, and [[solar radiation]]
|-
|'''[[neutron|Neutrons]]''' 
0.05 ev (thermal) 
1.0 MeV 
10 MeV
| 
2.8 
10.5 
6.4
|Nuclear interactions in the [[sun]]; on Mars, produced when [[cosmic radiation]] interacts with [[regolith]]
|-
|'''[[alpha particles|Alpha Particles]]''' 
5.0 MeV 
1.0 MeV
| 
15 
20
|[[Cosmic radiation]]
|-
|[[Heavy Ions|'''Heavy Ions''']]
|Varies widely
|[[Cosmic radiation]]
|}
(RBE is a measure of the damage done to living tissue, relative to gamma rays)

Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref> Solar radiation includes the same radiation types, but it a higher proportion of protons and its heavy primaries have lower energy levels. The high-energy heavy primaries in cosmic radiation can penetrate materials that effectively block lower-energy radiation<ref name=":1">Rapp D. (2006). Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars. Mars 2:46-71. <nowiki>https://doi.org/10.1555/mars.2006.0004</nowiki></ref>.

==Exposure limits==

===Limits for humans===
Exposure to dangerous levels of radiation causes [[radiation sickness]] and cancer. Any exposure to radiation, no matter how slight, poses some risk. Small dose - small risk of cancer. High dose - high risk of cancer. The average exposure to radiation on Earth due to natural sources is 6.2 mSv per year<ref name=":3">http://www.ans.org/pi/resources/dosechart/msv.php</ref>

Nevertheless, there are defined legal limits for exposure during work for several professional activities, such as for X-ray assistants, airplane personnel, etc. The International Commission on Radiation Protection recommends that occupational (work-related) radiation exposure be limited to 50 millisieverts (mSv) per year, and limited to 100 mSv over any 5-year period<ref>http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103</ref>. NASA's radiation dose limits for astronauts are established in NASA-STD-3001<ref>NASA. (2015). NASA Space Flight Human-System Standard Volume 1, Revision A: Crew Health. Retrieved from https://standards.nasa.gov/standard/nasa/nasa-std-3001-vol-1</ref>.

There is scientific uncertainty surrounding the health hazard from cosmic and solar radiation, because most past research on the health effects of radiation studied only x-rays and gamma rays<ref name=":1" />.

===Limits for plants===
"In general, plants are relatively radiation resistant when growing and extremely resistant as dormant seeds." Radiation would not interfere with raising plants as food sources, at least not on the time scales of exploration missions.<ref>National Research Council 1996. Radiation Hazards to Crews of Interplanetary Missions: Biological Issues and Research Strategies. Washington, DC: The National Academies Press. <nowiki>https://doi.org/10.17226/5540</nowiki>.</ref>

==Martian Environment==

===Effects of the Martian atmosphere===
Most SPE particles will be stopped by the atmosphere before they reach the surface. However, interactions with atmospheric particles can produce neutrons; those neutrons can reach the surface, so the health hazard is not eliminated.

Cosmic radiation protons are likely to penetrate the atmosphere. Cosmic ray heavy ions may fragment in the atmosphere, producing lower-mass ions that can still harm astronauts on the surface.

Mars' thin atmosphere allows more ultraviolet light to reach the surface, compared to Earth. However, habitat structural materials and standard space suits should be sufficient to protect humans from UV radiation.<ref name=":4">Beaty DW, Snook K, Carlton A, Eppler D, Farrell B, Heldmann J,...Zeitlin C, on behalf of the Mars Human Precursor Science Steering Group. (2005). An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Mission to Mars. Available at <nowiki>https://mepag.jpl.nasa.gov/reports/MHP_SSG_(06-02-05).pdf</nowiki></ref>

===Effects of regolith===
When cosmic radiation strikes regolith, it can cause the impacted atoms to emit their own radiation. Surrounding regolith particles absorb much of this radiation, with the exception of neutrons.

Neutrons generated in this way are called albedo neutrons. These neutrons have the potential to add substantially to the radiation dose for astronauts on the surface.<ref name=":4" />

===Dose received by an unprotected human on Mars===

====Cosmic radiation====
The equivalent dose rate from cosmic radiation on Earth's surface at sea level is 0.26 mSv per year<ref name=":3" />. Based on measurements made by the Curiosity rover, the corresponding figure for the surface of Mars is approximately 230 mSv/year<ref name=":0">Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, Ehresmann B, Rafkin S, Eigenbrode JL,...MSL Science Team. (2014). Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover. Science 343(6169). <nowiki>https://doi.org/10.1126/science.1244797</nowiki></ref>. More generally, one model estimated that the dose equivalent rate on the surface of Mars ranges from 156.4 mSv/year (at solar maximum) to 273.8 mSv/year (at solar minimum)<ref name=":2" /><ref>McKenna-Lawlor S, Goncalves P, Keating A, Reitz G, Matthia D. (2012). Overview of Energetic Particle Hazards During Prospective Manned Missions to Mars. Planetary and Space Science. 63: 123-132.</ref>. A 2005 report by the Mars Human Precursor Science Steering Group estimated that (at solar minimum) the dose from cosmic radiation would be 1.2 +/- 0.5 mSv/day; this includes 0.4 +/- 0.4 mSv/day from albedo neutrons.<ref name=":4" />

====Solar Proton Events====
Curiosity also measured the temporary increase in radiation during a single SPE. The results indicate an increase in equivalent dose rate of approximately 25% over a 1-day interval<ref name=":0" />. This figure will vary depending on the intensity of a particular SPE.

==Effect on material==
Radiation can change the properties of [[plastics]] and metals, making them brittle after a period of time.

==Protection==
[[Habitat|Habitats]] should be equipped with a [[radiation shielding]], thick enough to reduce the radiation to a level equal to Earth, that is, almost zero. Best protection may be achieved with houses built in natural [[caves]] or set into cliffs or hillsides.

[[Space suit]]s must be designed with radiation in mind. The suit should provide adequate shielding for the occupant. It may be necessary to design suits with several grades of protection. Suits designed for short-term use can carry lighter shielding which would reduce weight and improve maneuverability.

During severe radiation events, such as [[solar flare|solar flares]], surface [[settlement|settlements]] may use [[storm shelter|storm shelters]] with heavier than normal shielding.

"In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars." <ref name=":2">NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig '' Radiation Shielding Optimization on Mars '', https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf, Apr 2013.</ref>

"An in-situ shielding strategy will also be of little help unless several hundred g/cm2 of regolith is utilized. Such a strategy would probably require large scale excavation making it an unlikely candidate. Instead, the shielding strategy would rely primarily on material optimization. Options, such as replacing aluminum structures with high hydrogen content carbon composites, could be pursued." <ref name=":2" /> This opinion is open to argument as in-situ resources utilization for any type of settlement should make large amounts of regolith available for construction. It mainly is true for the very first level of habitats.

The use of g/cm2 can be translated into an equivalent thickness that depends on the material density. For martian regolith at 2000 kg/m3, a thickness of 1m of regolith is 200 g/cm2. Water (or ice) is 100 g/cm2. So the minimum covering for a long term settlement would be 5m or more. For water, although the radiation absorption is better the density is lower, so about the same thickness would be required for protection (to be discussed)

==References==
<references />

==External links==

*[http://www.ips.gov.au/ IPS:] [http://www.ips.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/guide-to-space-radiation.pdf A Guide to Space Radiation]
*[http://www.niauk.org/radiation-and-safety.html Nuclear Industry Association: Radiation, health and nuclear safety]
*[https://hesperia.gsfc.nasa.gov/sspvse/posters/DF_Smart/poster.pdf The frequency distribution of solar proton events: 5 solar cycles and 45 solar cycles]

[[Category:Radiation Protection]]

Solar radiation

2020-03-15T18:10:19Z

JimL: Moved information specific to solar radiation protection from the main Radiation page.

==Sources of solar radiation==
'''Solar [[radiation]]''' can be split into two varieties: ''electromagnetic'' and ''ionized particles''.

*The electromagnetic spectrum is radiated from a near-"Black Body" at 5800K.
*High energy ions can be excited by [[solar wind]] interactions and/or emitted directly from [[solar flares]] or subsequent [[Coronal Mass Ejections]]. A solar proton event (SPE) occurs when the intensity of this radiation temporarily spikes after a solar flare or CME. In an SPE, the intensity of particulate radiation can increase by up to 5 orders of magnitude over the normal level, with radiation returning to the baseline level after several days.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>

== Protection ==
Occasional [[Solar flares|solar flares]] produce particularly high doses. Some SPEs were observed by [[MARIE]] that were not seen by sensors near Earth due to the fact that SPEs are directional. Astronauts on Mars could be warned of SPEs by sensors closer to the Sun and presumably take shelter during these events. This would imply that an [[Early warning system (solar radiation)|Early Warning System]] (possibly a network of sensors in orbit around the sun or a single sensor in [[Lagrangian point]] L1) might be needed to ensure all SPEs threatening Mars were detected early enough.
{{SettlementIndex}}

{{stub}}

[[category:Radiation Protection]]
<references />

Radiation

2020-03-15T18:07:01Z

JimL:

[[Image:nuclear_warning_sign.png|right|Nuclear Danger Icon]]
Natural '''Radiation''' on [[Mars]] is much higher compared with [[Earth]]. The thin [[atmosphere]] provides only a small shielding effect against harmful [[solar radiation]] and [[cosmic radiation]]. Mars also lacks the [[magnetosphere]] that protects Earth.

The average natural radiation level on Mars is 24-30 rads or 240-300 mSv per year(needs checking and reference). This is about 40-50 times the average on Earth.

Occasional [[solar flares]] produce particularly high doses. Some Solar Proton Events (SPEs) were observed by [[MARIE]] that were not seen by sensors near Earth due to the fact that SPEs are directional. Astronauts on Mars could be warned of SPEs by sensors closer to the Sun and presumably take shelter during these events. This would imply an [[Early warning system (solar radiation)|Early Warning System]] (possibly a network of sensors in orbit around the sun or a single sensor in [[Lagrangian point]] L1) might be needed to ensure all SPEs threatening Mars were detected early enough.

1 millisievert [mSv] = 0.1 rad [rd]

==Types of Radiation==
Radiation comes in a variety of forms:<ref>http://www.nas.nasa.gov/About/Education/SpaceSettlement/designer/needs.html#SHIELDING</ref>
{| border="1"
|-
!Name
!Relative Biological Effectiveness (RBE)
!Source
|-
|'''[[X-ray|X-Rays]] and [[gamma ray|Gamma Rays]]'''
|1
|[[Radiation belts]], [[solar radiation]], and bremsstrahlung electrons
|-
|'''[[electron|Electrons]]'''
1.0 MeV 
0.1 MeV
| 
1 
1.08
|Radiation belts
|-
|'''[[proton|Protons]]''' 
100 MeV 
1.5 MeV 
0.1 MeV
| 
1-2 
8.5 
10
|[[Cosmic radiation]], inner-radiation belts, and [[solar radiation]]
|-
|'''[[neutron|Neutrons]]''' 
0.05 ev (thermal) 
1.0 MeV 
10 MeV
| 
2.8 
10.5 
6.4
|Nuclear interactions in the [[sun]]; on Mars, produced when [[cosmic radiation]] interacts with [[regolith]]
|-
|'''[[alpha particles|Alpha Particles]]''' 
5.0 MeV 
1.0 MeV
| 
15 
20
|[[Cosmic radiation]]
|-
|[[Heavy Ions|'''Heavy Ions''']]
|Varies widely
|[[Cosmic radiation]]
|}
(RBE is a measure of the damage done to living tissue, relative to gamma rays)

Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref> Solar radiation includes the same radiation types, but it a higher proportion of protons and its heavy primaries have lower energy levels. The high-energy heavy primaries in cosmic radiation can penetrate materials that effectively block lower-energy radiation<ref name=":1">Rapp D. (2006). Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars. Mars 2:46-71. <nowiki>https://doi.org/10.1555/mars.2006.0004</nowiki></ref>.

==Exposure limits==

===Limits for humans===
Exposure to dangerous levels of radiation causes [[radiation sickness]] and cancer. Any exposure to radiation, no matter how slight, poses some risk. Small dose - small risk of cancer. High dose - high risk of cancer. The average exposure to radiation on Earth due to natural sources is 6.2 mSv per year<ref name=":3">http://www.ans.org/pi/resources/dosechart/msv.php</ref>

Nevertheless, there are defined legal limits for exposure during work for several professional activities, such as for X-ray assistants, airplane personnel, etc. The International Commission on Radiation Protection recommends that occupational (work-related) radiation exposure be limited to 50 millisieverts (mSv) per year, and limited to 100 mSv over any 5-year period<ref>http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103</ref>. NASA's radiation dose limits for astronauts are established in NASA-STD-3001<ref>NASA. (2015). NASA Space Flight Human-System Standard Volume 1, Revision A: Crew Health. Retrieved from https://standards.nasa.gov/standard/nasa/nasa-std-3001-vol-1</ref>.

There is scientific uncertainty surrounding the health hazard from cosmic and solar radiation, because most past research on the health effects of radiation studied only x-rays and gamma rays<ref name=":1" />.

===Limits for plants===
"In general, plants are relatively radiation resistant when growing and extremely resistant as dormant seeds." Radiation would not interfere with raising plants as food sources, at least not on the time scales of exploration missions.<ref>National Research Council 1996. Radiation Hazards to Crews of Interplanetary Missions: Biological Issues and Research Strategies. Washington, DC: The National Academies Press. <nowiki>https://doi.org/10.17226/5540</nowiki>.</ref>

==Martian Environment==

===Effects of the Martian atmosphere===
Most SPE particles will be stopped by the atmosphere before they reach the surface. However, interactions with atmospheric particles can produce neutrons; those neutrons can reach the surface, so the health hazard is not eliminated.

Cosmic radiation protons are likely to penetrate the atmosphere. Cosmic ray heavy ions may fragment in the atmosphere, producing lower-mass ions that can still harm astronauts on the surface.

Mars' thin atmosphere allows more ultraviolet light to reach the surface, compared to Earth. However, habitat structural materials and standard space suits should be sufficient to protect humans from UV radiation.<ref name=":4">Beaty DW, Snook K, Carlton A, Eppler D, Farrell B, Heldmann J,...Zeitlin C, on behalf of the Mars Human Precursor Science Steering Group. (2005). An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Mission to Mars. Available at <nowiki>https://mepag.jpl.nasa.gov/reports/MHP_SSG_(06-02-05).pdf</nowiki></ref>

===Effects of regolith===
When cosmic radiation strikes regolith, it can cause the impacted atoms to emit their own radiation. Surrounding regolith particles absorb much of this radiation, with the exception of neutrons.

Neutrons generated in this way are called albedo neutrons. These neutrons have the potential to add substantially to the radiation dose for astronauts on the surface.<ref name=":4" />

===Dose received by an unprotected human on Mars===

====Cosmic radiation====
The equivalent dose rate from cosmic radiation on Earth's surface at sea level is 0.26 mSv per year<ref name=":3" />. Based on measurements made by the Curiosity rover, the corresponding figure for the surface of Mars is approximately 230 mSv/year<ref name=":0">Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, Ehresmann B, Rafkin S, Eigenbrode JL,...MSL Science Team. (2014). Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover. Science 343(6169). <nowiki>https://doi.org/10.1126/science.1244797</nowiki></ref>. More generally, one model estimated that the dose equivalent rate on the surface of Mars ranges from 156.4 mSv/year (at solar maximum) to 273.8 mSv/year (at solar minimum)<ref name=":2" /><ref>McKenna-Lawlor S, Goncalves P, Keating A, Reitz G, Matthia D. (2012). Overview of Energetic Particle Hazards During Prospective Manned Missions to Mars. Planetary and Space Science. 63: 123-132.</ref>. A 2005 report by the Mars Human Precursor Science Steering Group estimated that (at solar minimum) the dose from cosmic radiation would be 1.2 +/- 0.5 mSv/day; this includes 0.4 +/- 0.4 mSv/day from albedo neutrons.<ref name=":4" />

====Solar Proton Events====
Curiosity also measured the temporary increase in radiation during a single SPE. The results indicate an increase in equivalent dose rate of approximately 25% over a 1-day interval<ref name=":0" />. This figure will vary depending on the intensity of a particular SPE.

==Effect on material==
Radiation can change the properties of [[plastics]] and metals, making them brittle after a period of time.

==Protection==
[[Habitat|Habitats]] should be equipped with a [[radiation shielding]], thick enough to reduce the radiation to a level equal to Earth, that is, almost zero. Best protection may be achieved with houses built in natural [[caves]] or set into cliffs or hillsides.

[[Space suit]]s must be designed with radiation in mind. The suit should provide adequate shielding for the occupant. It may be necessary to design suits with several grades of protection. Suits designed for short-term use can carry lighter shielding which would reduce weight and improve maneuverability.

During severe radiation events, such as [[solar flare|solar flares]], surface [[settlement|settlements]] may use [[storm shelter|storm shelters]] with heavier than normal shielding.

"In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars." <ref name=":2">NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig '' Radiation Shielding Optimization on Mars '', https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf, Apr 2013.</ref>

"An in-situ shielding strategy will also be of little help unless several hundred g/cm2 of regolith is utilized. Such a strategy would probably require large scale excavation making it an unlikely candidate. Instead, the shielding strategy would rely primarily on material optimization. Options, such as replacing aluminum structures with high hydrogen content carbon composites, could be pursued." <ref name=":2" /> This opinion is open to argument as in-situ resources utilization for any type of settlement should make large amounts of regolith available for construction. It mainly is true for the very first level of habitats.

The use of g/cm2 can be translated into an equivalent thickness that depends on the material density. For martian regolith at 2000 kg/m3, a thickness of 1m of regolith is 200 g/cm2. Water (or ice) is 100 g/cm2. So the minimum covering for a long term settlement would be 5m or more. For water, although the radiation absorption is better the density is lower, so about the same thickness would be required for protection (to be discussed)

==References==
<references />

==External links==

*[http://www.ips.gov.au/ IPS:] [http://www.ips.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/guide-to-space-radiation.pdf A Guide to Space Radiation]
*[http://www.niauk.org/radiation-and-safety.html Nuclear Industry Association: Radiation, health and nuclear safety]
*[https://hesperia.gsfc.nasa.gov/sspvse/posters/DF_Smart/poster.pdf The frequency distribution of solar proton events: 5 solar cycles and 45 solar cycles]

[[Category:Radiation Protection]]

Radiation shielding

2020-03-01T18:55:44Z

JimL: /* Possible Shielding Materials */

What Mars Actually Looks Like!

2020-02-17T21:36:31Z

JimL: More formatting changes to improve alignment of photos and prevent headings from displaying alongside photos.

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Almost all of the sites that we have landed on Mars with spacecraft have been to the most drab and boring places on the planet. This was done to ensure a safe landing. This article will display many of the more exciting landscapes using HiRISE images. HiRISE images can show detail down to the size of a small kitchen table. With HiRISE we frequently even see spacecraft that have landed on the surface. Many of the scenes shown here are about one would see at the height of a helicopter.
Most of the HiRISE images here were obtained through the HiWish program, a program where anyone could suggest places to be imaged with HiRISE. To obtain the images, I studied wide angle CTX images to find sites that could contain interesting features. I was lucky that many of my suggestions were photographed, and I was able to gather them together for this article.

==Viking 1==

[[File:Mars Viking 11d128.png |thumb|300px|right|Rocks and dunes, as seen from Viking 1 Holes were dug by the digging tool. Part of the meteorology boom is visible. ]]
Viking 1 was the first successful spacecraft to land on Mars. It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E). July 20th was also the date when we first landed on the moon in 1969. 

==Viking 2==

[[File:Viking2lander1.jpg |thumb|300px|left| View from Viking 2 ]]
Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E). 

==Mars Pathfinder==

[[File:Mars pathfinder panorama large.jpg |thumb|300px|right|Wide view from Mars pathfinder, showing Sojourner Rover ]]
The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in [[Ares Vallis]]. 

==Spirit Rover==

The Spirit Rover landed on January 4, 2004 at 14.5684 S and 175.472636 E (184.527364 W).

<gallery class="center" widths="190px" heights="180px" >
File:Bonneville crater.jpg|Bonneville crater from Spirit Rover Columbia Hills are in the right in the distance. Spirit eventually drove to the Columbia Hills.
File:Free Spirit.jpg|Wide view with Husband Hill in the distance to which Spirit eventually drove to. Solar panels are visible.
File:MER A Spirit Everest L257atc-A622R1 br2.jpg|Wide view from Spirit Rover Solar panels are visible.
</gallery>

==Opportunity Rover==

The Opportunity Rover landed on January 25, 2004 at 1.9462 S and 354.4734 E (5.5268 W).

<gallery class="center" widths="190px" heights="180px" >

File:Opportunity Heat Shield.jpg|Wide view from Opportunity showing heat shield to the left and circular impact crater on the right
File:PIA21723-MarsOpportunityRover-PerserveranceValley-20170619.jpg|Wide view of Perserverance Valley taken with Opportunity Rover High points visible on the rim of Endeavour Crater include "Winnemucca" on the left and "Cape Tribulation" on the right. Winnemucca is part of the "Cape Byron" portion of the crater rim. The horizon at far right extends across the floor of Endeavour Crater, which is about 14 miles (22 kilometers) in diameter.
File:PIA19109-MarsOpportunityRover-EndeavourCrater-CapeTribulation-20150122.jpg|Wide view from top of the "Cape Tribulation" segment of the rim of Endeavour Crater.
</gallery>

==Phoenix==

[[File:PIA13804-MarsPhoenixLander-Panorama-20080525b.jpg |thumb|300px|left|Wide view from Phoenix lander Solar panels are visible.]]
Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis. 

==Curiosity Rover==
[[File:673885main PIA15986-full full.jpg |thumb|300px|right|Early view from Curiosity Mount Sharp is in the distance. The shadow of Rover is visible. Mount Sharp at a height of about 3.4 miles is taller than Mt. Whitney in California.]]
The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W). By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting. 

<gallery class="center" widths="190px" heights="180px" >

File:7623 mars-slip-face-downwind-sand-dune-namib-sol1196-pia20281-full2.jpg|Slip Face on Downwind Side of 'Namib' Sand Dune on Mars, as seen by Curiosity Dune stands about 13 feet (4 meters) high. Picture taken with Navcam.

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg|View from the "Kimberley" formation on Mars taken by NASA's Curiosity rover.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp Location is within the "Murray Buttes" region on lower Mount Sharp.

File:PIA23346 hireslayerscuriosity.jpg|360-degree panorama of a location called "Teal Ridge"

File:PIA23347 hireslayersclose.jpg|Close view of layers of ancient sediment on a boulder-sized rock called "Strathdon," as seen by the Mars Hand Lens Imager (MAHLI) camera on the end of the robotic arm on NASA's Curiosity rover.
</gallery>

What follows are a few pictures of the many different scenes that we have studied with powerful cameras on board the Mars Reconnaissance Orbiter that has been going around Mars for over 10 years.

==Dunes==

The Martian surface displays many beautiful dark dunes. For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds
How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

<gallery class="center" widths="190px" heights="180px" >

File:61974 1710dunesrgb2.jpg|Dunes processed in the rgb color system
File:ESP 044861 2225dunes.jpg|Wide view of dune field in Ismenius Lacus quadrangle
File:ESP 043821 2555dryice.jpg|Defrosting dunes in Mare Boreum quadrangle
File:ESP 043821 2555dryicecolor.jpg|Color view of dunes defrosting Ice is in the toughs of the polygons.
File:ESP 046378 1415dunefield.jpg|Wide view of dune field
File:46378 1415dunesirb.jpg|Close view of dunes
File:46378 1415dunesirb2.jpg|Close view of dunes

</gallery>

==Layers==

Many places on Mars show rocks arranged in layers. Volcanoes, wind, or water can produce layers.<ref>url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 </ref> Layers can be hardened by the action of groundwater.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater in Oxia Palus quadrangle, as seen by HiRISE under HiWish program

<gallery class="center" widths="300px">

File:Wikiesp 035896 1845crommelinbutte.jpg|thumb|300px|left|Layers in Crommelin Crater
File:544858 1885topcloselayers5.jpg|thumb|300px|center|Layers in Danielson Crater in Oxia Palus quadrangle
File:60331 1880layersclosecolor.jpg|thumb|right|300px|Color image of layers on the floor of Danielson Crater taken under the HiWish program
</gallery>
[[File:60331 1880widelayersdark.jpg|600pxr|Layers on the floor of Danielson Crater taken under the HiWish program Box shows size of a football field.]]

==Glaciers==

There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. A few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>

Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.<ref>Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127</ref> <ref>Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128</ref> <ref>Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671</ref> <ref>Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33</ref> Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> Lineated valley fill (LVF)are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines may have developed as other glaciers moved down valleys. Some of these glaciers seem to come from material sitting around mesas and buttes.<ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> Lobate debris aprons (LDA) is the name given to these glaciers. All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.<ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="190px" heights="180px" >
File:ESP 050176 2245glacier.jpg|Glacier leaving a valley in the Ismenius Lacus quadrangle
File:Hollows as seen by hirise under hiwish program.jpg|Concentric crater fill The concentric lines are formed from ice moving away from the crater walls. This crater is mostly full of ice.

Concentric Crater Fill Wide-view.jpg|Wide view of concentric crater fill in crater in Casius quadrangle
</gallery>

[[File:Wikildaf03 036777 2287.jpg|thumb|300px|center|Mesa with Lobate Debris Aprons (LDA) Orbiting radars have detected ice in LDA’s under a thin cover of debris.]]

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

[[File:ESP 045085 2205flowlabeled.jpg|thumb|300px|center|Labeled view of Lineated Valley Flow and glacier]]

<gallery class="center" widths="190px" heights="180px" >
File:ESP 046840 2130lvf.jpg|Lineated Valley Flow in valley
File:53630 2195lvf.jpg|Lineated Valley Flow, as seen by HiRISE under the HiWish program

</gallery>

==Gullies==

[[Martian gullies]] are networks of narrow channels and their associated downslope deposits, found on steep slopes. A high concentration occurs near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref name="Malin, M. 2000">Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. They were believed to be caused by recent running water, but with more observations it was shown that pieces of dry ice moving down slopes could cause them.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 039621 1315gullies.jpg|Gullies with alcove, channel, and apron labeled
File:47395 1415gullycurvedchannels.jpg|Gullies in Argyre quadrangle Curved channels were thought to need running water to form.

File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program
File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>
</gallery>

==Channels==

There are thousands of channels that were probably caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref>

<gallery class="center" widths="190px" heights="180px" >
WikiESP 033729 1410stream.jpg|Small branched channel
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel These were shaped by running water.
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.
</gallery>

==Troughs==

The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Troughs in Elysium Planitia.jpg|Troughs in the Elysium Planitia
File:ESP 051781 2035troughs.jpg|Troughs in Amenthes quadrangle
File:WikiESP 034541 2065pitstroughstharsis.jpg|Pits and troughs Troughs seem to start with lines of pits. Layers and dark slope streaks are also visible.

File:56910 2100trough.jpg|Troughs in the Cebrenia quadrangle, as seen by HiRISE under HiWish program
</gallery>

==Craters==

Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. So, impact craters are a major surface feature. There is a rich variety of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>

[[File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
|600pxr|Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.]]

Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.
File:26079secondaries.jpg|Group of secondary craters These are formed from material that is blasted way up in the air from the impact.
File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.
File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.
File:48131 2055pitsforming.jpg|Close view of pits on floor of crater A box shows the size of a football field. Note: This is an enlargement of the previous image of a crater.
File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>
File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.
File:ESP 052260 2165ringmold.jpg|Wide view of ring-mold crater on the floor of a larger crater
File:52260 2165ringmoldclose.jpg|Close view of ring-mold craters (indicated with arrows) Surface between the ring-mold craters is covered with brain terrain.
File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet.
File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
File:ESP 037528 2350pedestal.jpg|Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.
File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.

File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

</gallery>

==Scalloped Terrain==

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region of Utopia Planitia.<ref name=ref1>{{cite journal | last1 = Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 | bibcode=2009JGRE..114.4005L}}</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>http://www.uahirise.org/ESP_038821_1235</ref> Scalloped topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.<ref name="Dundas, C. 2015">{{cite journal | last1 = Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

<gallery class="center" widths="300px">
File:46916 2270scallopsmerging.jpg|Scalloped terrain in Casius quadrangle
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle
File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia
</gallery>
 
==Brain Terrain==

Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ribbed terrain==

Ribbed terrain forms as ice leaves the ground along cracks in a process called "
[[sublimation]]." Much of the ground is ice so that when the ice disappears the ground collapses.<ref>https://en.wikipedia.org/wiki/Upper_Plains_Unit</ref>

[[File:ESP 047499 2245ribswide.jpg |Wide view of ribbed terrain in Ismenius Lacus quadrangle
|600pxr|Wide view of ribbed terrain in Ismenius Lacus quadrangle]]

[[File:62002 1470ribbed.jpg|thumb|300px|left|Ribbed terrain]]

[[File:62002 1470ribbedclose2.jpg|thumb|300px|center|Ribbed terrain The box is the size of a football field]]

==Linear Ridge Networks==

[[File:46269 1770ridgesmesa.jpg|Close view of ridge network, as seen by HiRISE under HiWish program
|600pxr|Close view of ridge network, as seen by HiRISE under HiWish program]]

Close view of ridge network, as seen by HiRISE under HiWish program

This terrain appears over much of the planet. However, there is a heavy concentration of these features, also called irregular polygonal ridge networks, in the Nili Fossae region.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868.</ref> These networks consist of groups of narrow ridges that often meet at close to right angles. We are not sure of how it originated. It may have been caused by fluids moving into cracks that were created by impacts. The fluids then became hard and erosion resistant.<ref>Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref> <ref>Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276.</ref> <ref>Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.</ref> <ref>Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus: 281, 200-219.</ref> <ref>E. K. Ebinger E., J. Mustard. 2015. LINEAR RIDGES IN THE NILOSYRTIS REGION OF MARS: IMPLICATIONS FOR SUBSURFACE FLUID FLOW. 46th Lunar and Planetary Science Conference (2015) 2034.pdf</ref> <ref>Saper, L., J. Mustard. 2013. Extensive linear ridge networks in Nili Fossae and Nilosyrtis, Mars: implications for fluid flow in the ancient crust. Geophysical Research letters: 40, 245-249.</ref> <ref>Kerber L., Schwamb M., Portyankina G. Hansen C. J. Aye K.-M. Global Polygonal Ridge Networks: Evidence for Pervasive Noachian Crustal Groundwater Circulation [#2972]. pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2972.pdf49th</ref>

<gallery class="center" widths="190px" heights="180px" >
File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle
File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

File:46269 1770ridges2.jpg|Close view of ridge network
</gallery>

==Yardangs==

Yardangs form from fine-grained material. They are shaped by the wind and show the direction of the prevailing winds. Much of this fine-grained material probably has its origin in the many large volcanoes on the planet. Yardangs are especially common in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because they exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>

<gallery class="center" widths="190px" heights="180px" >
File:61167 1735yardangs3.jpg|Yardangs
File:35558 1830yardangs.jpg|Yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs in Amazonis quadrangle

</gallery>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface; consequently exposing a dark layer.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> The dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>
[[Image:dust_devils.gif|thumb|right|300px|Dust devils photographed by Mars Rover Spirit]]

<gallery class="center" widths="190px" heights="180px" >
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.

File:ESP 061787 2140devilcropped.jpg
</gallery>

==Dark Slope Streaks==

Dark slope streaks are avalanche-like features common on dust-covered slopes, especially in the equatorial regions.<ref name=Chuang10>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

<gallery class="center" widths="190px" heights="180px" >
File: ESP 045435 2055troughlayers.jpg | Dark slope streaks in trough Layers are also visible in the image.
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks
File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact
</gallery>

==Lava==

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Lava flows can also move around an create what appear to be layers, especially if it fluid like water. Basalt flows can often be that way.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="190px" heights="180px" >
File:ESP 044840 1620lavaflow.jpg|Lava flows in Phoenicis Lacus quadrangle
File:45133 1970lvarafts.jpg|Rafts of lava in Amazonis quadrangle
File:45384 2065cones.jpg|”Rootless cones” caused by lava flowing over ice-rich ground in Elysium quadrangle
</gallery>

==Mud Volcanoes==

Mud volcanoes are very common in the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold sources of evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Being underground the mud was protected from radiation on the surface. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

[[File:52050 2200mudvolcanoes.jpg |thumb|300px|left| Mud volcanoes in Mare Acidalium quadrangle]]

[[File:61584 2300mudvolcano.jpg|thumb|300px|right|Close view of mud volcano, as seen by HiRISE]]

[[File:53381 2265mud.jpg|thumb|300px|center|Mud volcanoes]]

==Rootless cones==

Rootless Cones are believed to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam which blows out a ring or cone. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form.

[[File:Wikiesp37643 2060cones.jpg|thumb|300px|right|Rootless cones formed when lava flowed over ice or ice-rich ground. The sharp bend in the line of cones may have been caused by the lava changing direction.]]

[[File:58610 2100cones.jpg|thumb|300px|left|Close view of rootless cones, as seen by HiRISE under the HiWish program]]

[[File:58610 2100coneswakeslabeled.jpg|300px|center|Close view of rootless cones showing wakes caused by lava moving]]

[[File:ESP 045384 2065lavaice.jpg|thumb|300px|center|Wide view of field of rootless cones in Elysium quadrangle]]

==Honeycomb Terrain==

[[File: ESP_049330_1425honeycomb.jpg|thumb|300px|right|Honeycomb terrain in Hellas quadrangle]]

Honeycomb terrain is found on parts of the floor of Hellas Planitia. It may be due to rising bodies of ice followed by erosion.<ref>Bernhardt, H.; et al. (2016). "The honeycomb terrain on the Hellas basin floor, mars: a case for salt or ice diapirism: hellas honeycombs as salt/ice diapirs". J. Geophys. Res. 121: 714–738.</ref> <ref>Weiss, D., J. Head. 2017. HYDROLOGY OF THE HELLAS BASIN AND THE EARLY MARS CLIMATE: WAS THE HONEYCOMB TERRAIN FORMED BY SALT OR ICE DIAPIRISM? Lunar and Planetary Science XLVIII. 1060.pdf</ref> <ref>Weiss, D.; Head, J. (2017). "Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate". Icarus. 284: 249–263.</ref>

 
==Fractured Surface and Blocks==

[[File:44757 2185closeleft.jpg |thumb|300px|left| Rock breaking up into cube-shaped blocks]]
In many places on Mars bedrock breaks up into large blocks. Sometimes the blocks form what look like perfect cubes. Although one may think these shapes had to be made by intelligent aliens, this is a natural process. The salt you put on your food also breaks up into cubes. Check your salt out with a magnifying glass.

 
==Fractured Ground==

Some places on Mars break up with large fractures that create a terrain with mesas and valleys. Some of these can be quite pretty.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 048878 2095fractures.jpg|Wide view of fractured ground
File:48878 2095fractures.jpg|Close view of fractured ground
</gallery>

==Dipping layers==

Groups of layers that are tilted are common in some areas of Mars. They represent material that once covered a wide area.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288</ref> The layers may be related to changes in the climate in the past. They may have been shaped by the wind.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 050793 1365pyramids.jpg| Wide view of layered features in Hellas quadrangle
File:50793 1365layers2.jpg|Close view of layered features in Hellas quadrangle Each layer may represent a change in the climate.
File:ESP 035801 2210pyramidsismenius.jpg|Tilted layers in Ismenius Lacus These sets of layers can often be seen leaning against slopes.
</gallery>

==Boulders==

Much of the surface of Mars is covered with hard, basalt volcanic rock. When the rock breaks down it often forms large boulders the size of houses.

<gallery class="center" widths="190px" heights="180px" >
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas in Elysium quadrangle Box shows size of football field.
File:ESP 045415 2220boulders.jpg|Color view of boulders
File:45575 2535dunebouldertracks.jpg| Close view of dunes showing boulders with arrows If you click on image to enlarge, you can see the tracks left by the boulders as they traveled down the dune.
</gallery>

==Hollows==

Some places on Mars have surfaces that are covered with hollows. Sometimes they form large holes, sometimes curved canyons. They can be pretty and would be fun to explore on foot in the future. This terrain may have developed from what has been called ribbed terrain. Either way, these scenes were caused as ice left the ground.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 043688 2245hollows.jpg|Wide view of hollows in ground, probably from ice leaving the ground
File:ESP 043688 2245closecolor.jpg|Close color view of hollows in ground, probably from ice leaving the ground
File:ESP 026042 1470hollows.jpg| Hollows in ground, probably from ice leaving the ground Location is Hellas Montes Region.
</gallery>

==Mesas==

Many, large areas of Mars have eroded such that there are many mesas. Some show layers. Mesas show how the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="190px" heights="180px" >
File:47441 1800mesaclose.jpg|Mesa with box showing size of football field
File:47421 1890bigbutte.jpg|Layered mesa with box showing size of football field
File:46050 1775race.jpg|Mesa that is 14 km or 8.7 miles around the outside
</gallery>

==Landslides==

Mars shows various mass movements like landslides. There are many steep slopes for material to move down, especially in craters and canyons.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 043963 1550landslide.jpg|Landslide
File:ESP 045981 1585landslide.jpg|Landslide

File:ESP 057191 2150landslidecropped.jpg|Landslide
</gallery>

==Latitude Dependent Mantle==

Latitude Dependent Mantle is very common in certain latitudes.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It often appears as a smooth covering. A certain percentage of it consists of ice. It may be a major source of water for future colonists because it has a widespread distribution. Sometimes mantle displays layers because it was deposited at different times.
<gallery class="center" widths="190px" heights="180px" >
File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program
File:2509mantlelayers.jpg|Mantle layers with layers
</gallery>

==Exhumed craters==

Exhumed craters seem to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

<gallery class="center" widths="190px" heights="180px">

File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters, as seen by HiRISE under HiWish program

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
</gallery>

==Swiss Cheese Terrain==

Parts of Mare Australe show pits that make the surface look like Swiss cheese.<ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap. These circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.<ref> Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

<gallery class="center" widths="300px">
File:South Pole Terrain.jpg|Swiss Cheese Terrain near South Pole, as seen by HiRISE
File:ESP 058515 0955closechanges.jpg|Changes in Swiss Cheese Terrain from August 2009 to January 2019
</gallery>

<gallery class="center" widths="500px">
File:ESP 014274 0955southpole3.jpg|wiss Cheese Terrain August 2009
File:ESP 058515 0955southpole2.jpg|Swiss Cheese Terrain January 2019
</gallery>

==Ice Cap Layers==

The northern ice cap of Mars displays many layers of ice that accumulated when the climate changed. These are visible when there is a canyon in the ice. The climate of Mars changes greatly due to the large changes in the tilt of Mars. Mars does not have a large moon to stabilize its' tilt.

<gallery class="center" widths="190px" heights="180px" >

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019.
</gallery>

==Spiders==

The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> This results in the appearance of dark plumes that are often blown in one direction by local winds. This dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>

<gallery class="center" widths="300px">
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
File:Spidersmarspedia.jpg|Close view of spiders
</gallery>

==Polygonal Patterned Ground==
Many surfaces on Mars display “polygonal patterned ground.” The polygons can be of different shapes and sizes. They are believed to be caused by ice in the ground. These may still be another marker for underground ice that could be used by future colonists. Before we land crews on Mars, we may very well have detailed maps for where the colonists can obtain water.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 049660 1200polygonswide.jpg|Wide view of large and small polygons

File:ESP 049660 1200polygonsclosecolor.jpg|Close, color view of polygons Note: this is an enlargement of the previous wide view image.
File:45070 1440polygonscloseshadows.jpg|High center polygons
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:56148 1145polygonswide.jpg|Wide view of crater floor that is covered with polygons Low places still contain frost. Image taken with HiRISE under HiWish program.

File:56148 1145polygonsclose.jpg|Enlarged view of polygons from previous image. Dark line is a defect in processing.
File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons from a previous image that shows polygons of varying sizes. Dark lines are defects in processing.
</gallery>

==Notes about pictures==

Most pictures from spacecraft have some sort of enhancement. For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red. Displaying colors in this way allows us to better identify rocks and minerals.
HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

[[File:60331 1880widecolorband.jpg|Wide view of layers in Danielson Crater The center band is in color|600pxr|Wide view of layers in Danielson Crater The center band is in color.]]
Wide view of layers in Danielson Crater The center band is in color.

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Dust devils]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[How living on Mars will be different than living on Earth]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Sublimation]]

* [[Sublimation landscapes on Mars]]

*[[Water]]

== External links ==

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]
* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground
* [https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

* [https://www.youtube.com/user/MARS3DdotCOM Flying around Candor Chasma at an altitude of 100 meters]

* [https://www.youtube.com/watch?v=Q-2B8J2OU8o Flight over Mars using HiRISE images--very beautiful]

* [https://www.youtube.com/watch?v=mBuvVM_e4G0 HiRISE images of polar regions with narriation]

* [https://www.youtube.com/watch?v=uZ5Y8Qc_dZU&index=2&list=PL2gLpWRK0QlAqGDSlMKS4BaJVbwzEl_0g HiRISE images of beautiful scenes]

* [https://www.youtube.com/watch?v=YIoVtsVsx0Y Flyover of many parts of Mars using HiRISE images--Very nice]

* [https://www.youtube.com/watch?v=siIoqdPG3U4 Pictures from HiRISE and from Curiosity ]

[[category:Areomorphology]]

What Mars Actually Looks Like!

2020-02-10T17:32:14Z

JimL: Adjusted formatting to improve alignment of images and headings.

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Almost all of the sites that we have landed on Mars with spacecraft have been to the most drab and boring places on the planet. This was done to ensure a safe landing. This article will display many of the more exciting landscapes using HiRISE images. HiRISE images can show detail down to the size of a small kitchen table. With HiRISE we frequently even see spacecraft that have landed on the surface. Many of the scenes shown here are about one would see at the height of a helicopter.
Most of the HiRISE images here were obtained through the HiWish program, a program where anyone could suggest places to be imaged with HiRISE. To obtain the images, I studied wide angle CTX images to find sites that could contain interesting features. I was lucky that many of my suggestions were photographed, and I was able to gather them together for this article.

==Viking 1==

[[File:Mars Viking 11d128.png |thumb|300px|right|Rocks and dunes, as seen from Viking 1 Holes were dug by the digging tool. Part of the meteorology boom is visible. ]]
Viking 1 was the first successful spacecraft to land on Mars. It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E). July 20th was also the date when we first landed on the moon in 1969. 

==Viking 2==

[[File:Viking2lander1.jpg |thumb|300px|left| View from Viking 2 ]]
Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E). 

==Mars Pathfinder==

[[File:Mars pathfinder panorama large.jpg |thumb|300px|right|Wide view from Mars pathfinder, showing Sojourner Rover ]]
The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in [[Ares Vallis]]. 

==Spirit Rover==

The Spirit Rover landed on January 4, 2004 at 14.5684 S and 175.472636 E (184.527364 W).

<gallery class="center" widths="190px" heights="180px" >
File:Bonneville crater.jpg|Bonneville crater from Spirit Rover Columbia Hills are in the right in the distance. Spirit eventually drove to the Columbia Hills.
File:Free Spirit.jpg|Wide view with Husband Hill in the distance to which Spirit eventually drove to. Solar panels are visible.
File:MER A Spirit Everest L257atc-A622R1 br2.jpg|Wide view from Spirit Rover Solar panels are visible.
</gallery>

==Opportunity Rover==

The Opportunity Rover landed on January 25, 2004 at 1.9462 S and 354.4734 E (5.5268 W).

<gallery class="center" widths="190px" heights="180px" >

File:Opportunity Heat Shield.jpg|Wide view from Opportunity showing heat shield to the left and circular impact crater on the right
File:PIA21723-MarsOpportunityRover-PerserveranceValley-20170619.jpg|Wide view of Perserverance Valley taken with Opportunity Rover High points visible on the rim of Endeavour Crater include "Winnemucca" on the left and "Cape Tribulation" on the right. Winnemucca is part of the "Cape Byron" portion of the crater rim. The horizon at far right extends across the floor of Endeavour Crater, which is about 14 miles (22 kilometers) in diameter.
File:PIA19109-MarsOpportunityRover-EndeavourCrater-CapeTribulation-20150122.jpg|Wide view from top of the "Cape Tribulation" segment of the rim of Endeavour Crater.
</gallery>

==Phoenix==

[[File:PIA13804-MarsPhoenixLander-Panorama-20080525b.jpg |thumb|300px|left|Wide view from Phoenix lander Solar panels are visible.]]
Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis. 

==Curiosity Rover==
[[File:673885main PIA15986-full full.jpg |thumb|300px|right|Early view from Curiosity Mount Sharp is in the distance. The shadow of Rover is visible. Mount Sharp at a height of about 3.4 miles is taller than Mt. Whitney in California.]]
The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W). By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting. 

<gallery class="center" widths="190px" heights="180px" >

File:7623 mars-slip-face-downwind-sand-dune-namib-sol1196-pia20281-full2.jpg|Slip Face on Downwind Side of 'Namib' Sand Dune on Mars, as seen by Curiosity Dune stands about 13 feet (4 meters) high. Picture taken with Navcam.

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg|View from the "Kimberley" formation on Mars taken by NASA's Curiosity rover.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp Location is within the "Murray Buttes" region on lower Mount Sharp.

File:PIA23346 hireslayerscuriosity.jpg|360-degree panorama of a location called "Teal Ridge"

File:PIA23347 hireslayersclose.jpg|Close view of layers of ancient sediment on a boulder-sized rock called "Strathdon," as seen by the Mars Hand Lens Imager (MAHLI) camera on the end of the robotic arm on NASA's Curiosity rover.
</gallery>

What follows are a few pictures of the many different scenes that we have studied with powerful cameras on board the Mars Reconnaissance Orbiter that has been going around Mars for over 10 years.

==Dunes==

The Martian surface displays many beautiful dark dunes. For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds
How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

<gallery class="center" widths="190px" heights="180px" >

File:61974 1710dunesrgb2.jpg|Dunes processed in the rgb color system
File:ESP 044861 2225dunes.jpg|Wide view of dune field in Ismenius Lacus quadrangle
File:ESP 043821 2555dryice.jpg|Defrosting dunes in Mare Boreum quadrangle
File:ESP 043821 2555dryicecolor.jpg|Color view of dunes defrosting Ice is in the toughs of the polygons.
File:ESP 046378 1415dunefield.jpg|Wide view of dune field
File:46378 1415dunesirb.jpg|Close view of dunes
File:46378 1415dunesirb2.jpg|Close view of dunes

</gallery>

==Layers==

Many places on Mars show rocks arranged in layers. Volcanoes, wind, or water can produce layers.<ref>url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 </ref> Layers can be hardened by the action of groundwater.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater in Oxia Palus quadrangle, as seen by HiRISE under HiWish program

<gallery class="center" widths="300px">

File:Wikiesp 035896 1845crommelinbutte.jpg|thumb|300px|left|Layers in Crommelin Crater
File:544858 1885topcloselayers5.jpg|thumb|300px|center|Layers in Danielson Crater in Oxia Palus quadrangle
File:60331 1880layersclosecolor.jpg|thumb|right|300px|Color image of layers on the floor of Danielson Crater taken under the HiWish program
</gallery>
[[File:60331 1880widelayersdark.jpg|600pxr|Layers on the floor of Danielson Crater taken under the HiWish program Box shows size of a football field.]]

==Glaciers==

There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. A few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>

Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.<ref>Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127</ref> <ref>Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128</ref> <ref>Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671</ref> <ref>Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33</ref> Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> Lineated valley fill (LVF)are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines may have developed as other glaciers moved down valleys. Some of these glaciers seem to come from material sitting around mesas and buttes.<ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> Lobate debris aprons (LDA) is the name given to these glaciers. All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.<ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="190px" heights="180px" >
File:ESP 050176 2245glacier.jpg|Glacier leaving a valley in the Ismenius Lacus quadrangle
File:Hollows as seen by hirise under hiwish program.jpg|Concentric crater fill The concentric lines are formed from ice moving away from the crater walls. This crater is mostly full of ice.

Concentric Crater Fill Wide-view.jpg|Wide view of concentric crater fill in crater in Casius quadrangle
</gallery>

[[File:Wikildaf03 036777 2287.jpg|thumb|300px|center|Mesa with Lobate Debris Aprons (LDA) Orbiting radars have detected ice in LDA’s under a thin cover of debris.]]

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

[[File:ESP 045085 2205flowlabeled.jpg|thumb|300px|center|Labeled view of Lineated Valley Flow and glacier]]

<gallery class="center" widths="190px" heights="180px" >
File:ESP 046840 2130lvf.jpg|Lineated Valley Flow in valley
File:53630 2195lvf.jpg|Lineated Valley Flow, as seen by HiRISE under the HiWish program

</gallery>

==Gullies==

[[Martian gullies]] are networks of narrow channels and their associated downslope deposits, found on steep slopes. A high concentration occurs near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref name="Malin, M. 2000">Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. They were believed to be caused by recent running water, but with more observations it was shown that pieces of dry ice moving down slopes could cause them.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 039621 1315gullies.jpg|Gullies with alcove, channel, and apron labeled
File:47395 1415gullycurvedchannels.jpg|Gullies in Argyre quadrangle Curved channels were thought to need running water to form.

File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program
File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>
</gallery>

==Channels==

There are thousands of channels that were probably caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref>

<gallery class="center" widths="190px" heights="180px" >
WikiESP 033729 1410stream.jpg|Small branched channel
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel These were shaped by running water.
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.
</gallery>

==Troughs==

The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Troughs in Elysium Planitia.jpg|Troughs in the Elysium Planitia
File:ESP 051781 2035troughs.jpg|Troughs in Amenthes quadrangle
File:WikiESP 034541 2065pitstroughstharsis.jpg|Pits and troughs Troughs seem to start with lines of pits. Layers and dark slope streaks are also visible.

File:56910 2100trough.jpg|Troughs in the Cebrenia quadrangle, as seen by HiRISE under HiWish program
</gallery>

==Craters==

Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. So, impact craters are a major surface feature. There is a rich variety of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>

[[File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
|600pxr|Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.]]

Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.
File:26079secondaries.jpg|Group of secondary craters These are formed from material that is blasted way up in the air from the impact.
File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.
File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.
File:48131 2055pitsforming.jpg|Close view of pits on floor of crater A box shows the size of a football field. Note: This is an enlargement of the previous image of a crater.
File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>
File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.
File:ESP 052260 2165ringmold.jpg|Wide view of ring-mold crater on the floor of a larger crater
File:52260 2165ringmoldclose.jpg|Close view of ring-mold craters (indicated with arrows) Surface between the ring-mold craters is covered with brain terrain.
File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet.
File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
File:ESP 037528 2350pedestal.jpg|Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.
File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.

File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

</gallery>

==Scalloped Terrain==

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region of Utopia Planitia.<ref name=ref1>{{cite journal | last1 = Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 | bibcode=2009JGRE..114.4005L}}</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>http://www.uahirise.org/ESP_038821_1235</ref> Scalloped topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.<ref name="Dundas, C. 2015">{{cite journal | last1 = Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

[[File:46916 2270scallopsmerging.jpg| |thumb|300px|left|Scalloped terrain in Casius quadrangle ]]

[[File:37461 2255scallopedscale.jpg| thumb|300px|center|Scalloped terrain in Utopia Planitia in the Casius quadrangle]]

[[File:37461 2255scallopedclose.jpg| thumb|300px|right|Scalloped terrain in Utopia Planitia]]

==Brain Terrain==

Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ribbed terrain==

Ribbed terrain forms as ice leaves the ground along cracks in a process called "
[[sublimation]]." Much of the ground is ice so that when the ice disappears the ground collapses.<ref>https://en.wikipedia.org/wiki/Upper_Plains_Unit</ref>

[[File:ESP 047499 2245ribswide.jpg |Wide view of ribbed terrain in Ismenius Lacus quadrangle
|600pxr|Wide view of ribbed terrain in Ismenius Lacus quadrangle]]

[[File:62002 1470ribbed.jpg|thumb|300px|left|Ribbed terrain]]

[[File:62002 1470ribbedclose2.jpg|thumb|300px|center|Ribbed terrain The box is the size of a football field]]

==Linear Ridge Networks==

[[File:46269 1770ridgesmesa.jpg|Close view of ridge network, as seen by HiRISE under HiWish program
|600pxr|Close view of ridge network, as seen by HiRISE under HiWish program]]

Close view of ridge network, as seen by HiRISE under HiWish program

This terrain appears over much of the planet. However, there is a heavy concentration of these features, also called irregular polygonal ridge networks, in the Nili Fossae region.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868.</ref> These networks consist of groups of narrow ridges that often meet at close to right angles. We are not sure of how it originated. It may have been caused by fluids moving into cracks that were created by impacts. The fluids then became hard and erosion resistant.<ref>Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref> <ref>Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276.</ref> <ref>Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.</ref> <ref>Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus: 281, 200-219.</ref> <ref>E. K. Ebinger E., J. Mustard. 2015. LINEAR RIDGES IN THE NILOSYRTIS REGION OF MARS: IMPLICATIONS FOR SUBSURFACE FLUID FLOW. 46th Lunar and Planetary Science Conference (2015) 2034.pdf</ref> <ref>Saper, L., J. Mustard. 2013. Extensive linear ridge networks in Nili Fossae and Nilosyrtis, Mars: implications for fluid flow in the ancient crust. Geophysical Research letters: 40, 245-249.</ref> <ref>Kerber L., Schwamb M., Portyankina G. Hansen C. J. Aye K.-M. Global Polygonal Ridge Networks: Evidence for Pervasive Noachian Crustal Groundwater Circulation [#2972]. pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2972.pdf49th</ref>

<gallery class="center" widths="190px" heights="180px" >
File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle
File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

File:46269 1770ridges2.jpg|Close view of ridge network
</gallery>

==Yardangs==

Yardangs form from fine-grained material. They are shaped by the wind and show the direction of the prevailing winds. Much of this fine-grained material probably has its origin in the many large volcanoes on the planet. Yardangs are especially common in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because they exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>

<gallery class="center" widths="190px" heights="180px" >
File:61167 1735yardangs3.jpg|Yardangs
File:35558 1830yardangs.jpg|Yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs in Amazonis quadrangle

</gallery>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface; consequently exposing a dark layer.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>
[[Image:dust_devils.gif|thumb|right|300px|Dust devils photographed by Mars Rover Spirit]]

<gallery class="center" widths="190px" heights="180px" >
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.
</gallery>

==Dark Slope Streaks==

Dark slope streaks are avalanche-like features common on dust-covered slopes, especially in the equatorial regions.<ref name=Chuang10>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

<gallery class="center" widths="190px" heights="180px" >
File: ESP 045435 2055troughlayers.jpg | Dark slope streaks in trough Layers are also visible in the image.
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks
File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact
</gallery>

==Lava==

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Lava flows can also move around an create what appear to be layers, especially if it fluid like water. Basalt flows can often be that way.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="190px" heights="180px" >
File:ESP 044840 1620lavaflow.jpg|Lava flows in Phoenicis Lacus quadrangle
File:45133 1970lvarafts.jpg|Rafts of lava in Amazonis quadrangle
File:45384 2065cones.jpg|”Rootless cones” caused by lava flowing over ice-rich ground in Elysium quadrangle
</gallery>

==Mud Volcanoes==

Mud volcanoes are very common in the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold sources of evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Being underground the mud was protected from radiation on the surface. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

[[File:52050 2200mudvolcanoes.jpg |thumb|300px|left| Mud volcanoes in Mare Acidalium quadrangle]]

[[File:61584 2300mudvolcano.jpg|thumb|300px|right|Close view of mud volcano, as seen by HiRISE]]

[[File:53381 2265mud.jpg|thumb|300px|center|Mud volcanoes]]

==Rootless cones==

Rootless Cones are believed to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam which blows out a ring or cone. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form.

[[File:Wikiesp37643 2060cones.jpg|thumb|300px|right|Rootless cones formed when lava flowed over ice or ice-rich ground. The sharp bend in the line of cones may have been caused by the lava changing direction.]]

[[File:58610 2100cones.jpg|thumb|300px|left|Close view of rootless cones, as seen by HiRISE under the HiWish program]]

[[File:58610 2100coneswakeslabeled.jpg|300px|center|Close view of rootless cones showing wakes caused by lava moving]]

[[File:ESP 045384 2065lavaice.jpg|thumb|300px|center|Wide view of field of rootless cones in Elysium quadrangle]]

==Honeycomb Terrain==

Honeycomb terrain is found on parts of the floor of Hellas Planitia. It may be due to rising bodies of ice followed by erosion.<ref>Bernhardt, H.; et al. (2016). "The honeycomb terrain on the Hellas basin floor, mars: a case for salt or ice diapirism: hellas honeycombs as salt/ice diapirs". J. Geophys. Res. 121: 714–738.</ref> <ref>Weiss, D., J. Head. 2017. HYDROLOGY OF THE HELLAS BASIN AND THE EARLY MARS CLIMATE: WAS THE HONEYCOMB TERRAIN FORMED BY SALT OR ICE DIAPIRISM? Lunar and Planetary Science XLVIII. 1060.pdf</ref> <ref>Weiss, D.; Head, J. (2017). "Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate". Icarus. 284: 249–263.</ref>

[[File: ESP_049330_1425honeycomb.jpg|thumb|300px|right|Honeycomb terrain in Hellas quadrangle]]

==Fractured Surface and Blocks==

In many places on Mars bedrock breaks up into large blocks. Sometimes the blocks form what look like perfect cubes. Although one may think these shapes had to be made by intelligent aliens, this is a natural process. The salt you put on your food also breaks up into cubes. Check your salt out with a magnifying glass.
[[File:44757 2185closeleft.jpg |thumb|300px|left| Rock breaking up into cube-shaped blocks]]

==Fractured Ground==

Some places on Mars break up with large fractures that create a terrain with mesas and valleys. Some of these can be quite pretty.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 048878 2095fractures.jpg|Wide view of fractured ground
File:48878 2095fractures.jpg|Close view of fractured ground
</gallery>

==Dipping layers==

Groups of layers that are tilted are common in some areas of Mars. They represent material that once covered a wide area.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288</ref> The layers may be related to changes in the climate in the past. They may have been shaped by the wind.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 050793 1365pyramids.jpg| Wide view of layered features in Hellas quadrangle
File:50793 1365layers2.jpg|Close view of layered features in Hellas quadrangle Each layer may represent a change in the climate.
File:ESP 035801 2210pyramidsismenius.jpg|Tilted layers in Ismenius Lacus These sets of layers can often be seen leaning against slopes.
</gallery>

==Boulders==

Much of the surface of Mars is covered with hard, basalt volcanic rock. When the rock breaks down it often forms large boulders the size of houses.

<gallery class="center" widths="190px" heights="180px" >
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas in Elysium quadrangle Box shows size of football field.
File:ESP 045415 2220boulders.jpg|Color view of boulders
File:45575 2535dunebouldertracks.jpg| Close view of dunes showing boulders with arrows If you click on image to enlarge, you can see the tracks left by the boulders as they traveled down the dune.
</gallery>

==Hollows==

Some places on Mars have surfaces that are covered with hollows. Sometimes they form large holes, sometimes curved canyons. They can be pretty and would be fun to explore on foot in the future. This terrain may have developed from what has been called ribbed terrain. Either way, these scenes were caused as ice left the ground.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 043688 2245hollows.jpg|Wide view of hollows in ground, probably from ice leaving the ground
File:ESP 043688 2245closecolor.jpg|Close color view of hollows in ground, probably from ice leaving the ground
File:ESP 026042 1470hollows.jpg| Hollows in ground, probably from ice leaving the ground Location is Hellas Montes Region.
</gallery>

==Mesas==

Many, large areas of Mars have eroded such that there are many mesas. Some show layers. Mesas show how the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="190px" heights="180px" >
File:47441 1800mesaclose.jpg|Mesa with box showing size of football field
File:47421 1890bigbutte.jpg|Layered mesa with box showing size of football field
File:46050 1775race.jpg|Mesa that is 14 km or 8.7 miles around the outside
</gallery>

==Landslides==

Mars shows various mass movements like landslides. There are many steep slopes for material to move down, especially in craters and canyons.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 043963 1550landslide.jpg|Landslide
File:ESP 045981 1585landslide.jpg|Landslide

File:ESP 057191 2150landslidecropped.jpg|Landslide
</gallery>

==Latitude Dependent Mantle==

Latitude Dependent Mantle is very common in certain latitudes.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It often appears as a smooth covering. A certain percentage of it consists of ice. It may be a major source of water for future colonists because it has a widespread distribution. Sometimes mantle displays layers because it was deposited at different times.
<gallery class="center" widths="190px" heights="180px" >
File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program
File:2509mantlelayers.jpg|Mantle layers with layers
</gallery>

==Exhumed craters==

Exhumed craters seem to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

<gallery class="center" widths="190px" heights="180px">

File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters, as seen by HiRISE under HiWish program

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
</gallery>

==Swiss Cheese Terrain==

Parts of Mare Australe show pits that make the surface look like Swiss cheese.<ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap. These circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.<ref> Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

[[File:South Pole Terrain.jpg|thumb|300px|center| Swiss Cheese Terrain near South Pole, as seen by HiRISE]]

[[File:ESP 058515 0955closechanges.jpg|thumb|300px|center|Changes in Swiss Cheese Terrain from August 2009 to January 2019]]

[[File:ESP 014274 0955southpole3.jpg|thumb|500px|left|Swiss Cheese Terrain August 2009]]

[[File:ESP 058515 0955southpole2.jpg|thumb|500px|center|Swiss Cheese Terrain January 2019]]

==Ice Cap Layers==

The northern ice cap of Mars displays many layers of ice that accumulated when the climate changed. These are visible when there is a canyon in the ice. The climate of Mars changes greatly due to the large changes in the tilt of Mars. Mars does not have a large moon to stabilize its' tilt.

<gallery class="center" widths="190px" heights="180px" >

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019.
</gallery>

==Spiders==

The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> This results in the appearance of dark plumes that are often blown in one direction by local winds. This dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>

[[File:47609 0985spiders.jpg|thumb|300px|right| Spiders and plumes, as seen by HiRISE under HiWish program ]]

[[File:Spidersmarspedia.jpg|thumb|300px|center|Close view of spiders]]

==Polygonal Patterned Ground==
Many surfaces on Mars display “polygonal patterned ground.” The polygons can be of different shapes and sizes. They are believed to be caused by ice in the ground. These may still be another marker for underground ice that could be used by future colonists. Before we land crews on Mars, we may very well have detailed maps for where the colonists can obtain water.

<gallery class="center" widths="190px" heights="180px" >
File:ESP 049660 1200polygonswide.jpg|Wide view of large and small polygons

File:ESP 049660 1200polygonsclosecolor.jpg|Close, color view of polygons Note: this is an enlargement of the previous wide view image.
File:45070 1440polygonscloseshadows.jpg|High center polygons
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:56148 1145polygonswide.jpg|Wide view of crater floor that is covered with polygons Low places still contain frost. Image taken with HiRISE under HiWish program.

File:56148 1145polygonsclose.jpg|Enlarged view of polygons from previous image. Dark line is a defect in processing.
File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons from a previous image that shows polygons of varying sizes. Dark lines are defects in processing.
</gallery>

==Notes about pictures==

Most pictures from spacecraft have some sort of enhancement. For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red. Displaying colors in this way allows us to better identify rocks and minerals.
HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

[[File:60331 1880widecolorband.jpg|Wide view of layers in Danielson Crater The center band is in color|600pxr|Wide view of layers in Danielson Crater The center band is in color.]]
Wide view of layers in Danielson Crater The center band is in color.

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Dust devils]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[How living on Mars will be different than living on Earth]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Sublimation]]

* [[Sublimation landscapes on Mars]]

*[[Water]]

== External links ==

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]
* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground
* [https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

* [https://www.youtube.com/user/MARS3DdotCOM Flying around Candor Chasma at an altitude of 100 meters]

* [https://www.youtube.com/watch?v=Q-2B8J2OU8o Flight over Mars using HiRISE images--very beautiful]

* [https://www.youtube.com/watch?v=mBuvVM_e4G0 HiRISE images of polar regions with narriation]

* [https://www.youtube.com/watch?v=uZ5Y8Qc_dZU&index=2&list=PL2gLpWRK0QlAqGDSlMKS4BaJVbwzEl_0g HiRISE images of beautiful scenes]

* [https://www.youtube.com/watch?v=YIoVtsVsx0Y Flyover of many parts of Mars using HiRISE images--Very nice]

* [https://www.youtube.com/watch?v=siIoqdPG3U4 Pictures from HiRISE and from Curiosity ]

[[category:Areomorphology]]

Radiation shielding

2020-02-02T20:08:23Z

JimL: Added table of candidate passive shielding materials.

Areomorphology

2020-01-27T16:36:45Z

JimL: Added an external link to a USGS map with morphology information.

[[Category:Areology]]
'''Areomorphology''', or '''geomorphology of Mars''', is the study of physical surface features on Mars.

The scientific study of the origin and evolution of topographic features on [[Mars]] created by physical, chemical, or potential biological processes operating at or near the planet's surface.

*Plate tectonics
*Wind erosion
*[[Water|Water erosion]]

==Etymology==
The Greek root of the term is Ares, the greek name for the god of war. ''Morphḗ'' means "form" and λόγος, ''lógos'', means "study."

== External Links ==
[https://pubs.usgs.gov/sim/3292/ USGS Geologic Map of Mars]

Heavy Ions

2020-01-08T20:42:47Z

JimL: Tried to improve explanation of RBE.

Heavy ions are charged particles heavier than alpha particles.<ref>Heavy ion. (1998, Jul 20). In ''Encyclopaedia Britannica. <nowiki>https://www.britannica.com/science/heavy-ion</nowiki>''</ref> They constitute 1% of [[cosmic radiation]].<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>

==Exposures==
[[File:Heavy ions in GCR.png|thumb|<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>Abundances and energies of heavy ions in cosmic radiation.|470x470px|alt=]]The left-hand graph shows which elements make up the heavy ions in cosmic radiation. The right-hand graph shows the distribution of energy levels for 4 ions. For example, carbon is one of the more abundant ions in cosmic radiation, and the most likely kinetic energy level for a carbon ion falls between 100 and 1000 MeV.
 
 
 
 
 
 
 

==Health Effects==
[[File:Cucinotta 2009 Fig. 4-3.png|thumb|412x412px|<ref name=":0">Cucinotta FA, Durante M. (2009). Risk of Radiation Carcinogenesis. In ''Human Health and Performance Risks of Space Exploration Missions''. NASA-SP-2009-3405. <nowiki>https://humanresearchroadmap.nasa.gov/Evidence/reports/EvidenceBook.pdf</nowiki></ref>Comparison of the ionization effects on nearby molecules produced by ions with different masses.]]

The effects of high doses of x-rays and gamma rays have been studied thoroughly by analyzing the health of exposed groups.<ref name=":1">Goodhead DT. (2018, Jun 8). Track Structure and the Quality Factor for Space Radiation Cancer Risk. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20180006105</nowiki></ref> However, in the case of alpha particles and especially heavy ion radiation, exposures on earth are very rare, and estimates of the risk to astronauts are derived solely from animal model and cell culture studies and application of biophysics principles.<ref name=":0" />

Heavy ions passing through cells transfer more energy into a small volume, compared to other components of cosmic radiation. This concentrated effect can produce qualitatively different types of cell damage.<ref name=":0" />

Linear energy transfer (LET) is a measure of the amount of energy deposited in tissue per unit length of a particle's trajectory.<ref>Wagenaar JD. (1995, Oct 6). Linear Energy Transfer. In ''Radiation Physics Principles'' (Section 7.2.3). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.2/7_2.3.html</nowiki></ref> LET increases as a function of ion charge, and decreases as a function of velocity.<ref>Wagenaar JD. (1995, Oct 6). Stopping Power. In Radiation Physics Principles (Section 7.1.2). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.1/7_1.2.html</nowiki></ref> Experimental irradiation of mouse cell cultures has indicated that heavy ions with an LET greater than 10 keV/μm are more likely to cause irreparable cell damage, compared to protons or alpha particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M-H, Shinn JL, & Badavi FF. (1997, Dec). In JW Wilson, J Miller, A Konradi, & FA Cucinotta, (Eds.), ''Shielding Strategies for Human Space Exploration'' (pp. 109-149). NASA Conference Publication 3360. <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref>

=== Relative Biological Effectiveness ===
Relative biological effectiveness (RBE) is a number that indicates how harmful a type of radiation is, compared to the same dose of gamma rays.

The RBE of heavy ion radiation is not fully understood. RBE for heavy ions appears to increase with LET, up to around 100-200 KeV/um. For LET levels above 100-200 KeV/um, the relationship between LET and RBE depends on the effect studied. If cell mutation or death is measured, RBE peaks at a factor of 2 to 3, and actually decreases as LET increases above 200 KeV/um. However, one study of tumor formation found that RBE peaked at a factor of 30, and plateaued as LET increased beyond 200 KeV/um.<ref>National Research Council 1996. Radiation Hazards to Crews of Interplanetary Missions: Biological Issues and Research Strategies. Washington, DC: The National Academies Press. <nowiki>https://doi.org/10.17226/5540</nowiki>.</ref> The LET of cosmic radiation ranges up to around 5,000 KeV/um, so it is important to accurately estimate RBE values up to that level.

NASA has developed an RBE estimate, the "NASA quality factor," which is based on a revised math formula that is designed to better account for the properties of heavy ion radiation that are normally ignored because they are not relevant on the Earth's surface.<ref name=":1" />

==Shielding Considerations==
Heavy ions generate secondary radiation due to the very high energy of the particles. This means the thickness of radiation shielding needs to be increased over the requirements of solar storm shelters. This is particularly a consideration for long term settlements, where the accumulation of radiation damage from inadequate shielding might lead to increased cancer rates, neurological, and tissue damage over time.

==References==
<references />

Radiation

2020-01-08T20:24:57Z

JimL: Information on UV radiation added.

[[Image:nuclear_warning_sign.png|right|Nuclear Danger Icon]]
Natural '''Radiation''' on [[Mars]] is much higher compared with [[Earth]]. The thin [[atmosphere]] provides only a small shielding effect against harmful [[solar radiation]] and [[cosmic radiation]]. Mars also lacks the [[magnetosphere]] that protects Earth.

The average natural radiation level on Mars is 24-30 rads or 240-300 mSv per year(needs checking and reference). This is about 40-50 times the average on Earth.

Occasional [[solar flares]] produce particularly high doses. Some Solar Proton Events (SPEs) were observed by [[MARIE]] that were not seen by sensors near Earth due to the fact that SPEs are directional. Astronauts on Mars could be warned of SPEs by sensors closer to the Sun and presumably take shelter during these events. This would imply an [[Early warning system (solar radiation)|Early Warning System]] (possibly a network of sensors in orbit around the sun or a single sensor in [[Lagrangian point]] L1) might be needed to ensure all SPEs threatening Mars were detected early enough.

1 millisievert [mSv] = 0.1 rad [rd]

==Types of Radiation==
Radiation comes in a variety of forms:<ref>http://www.nas.nasa.gov/About/Education/SpaceSettlement/designer/needs.html#SHIELDING</ref>
{| border="1"
|-
!Name
!Relative Biological Effectiveness (RBE)
!Source
|-
|'''[[X-ray|X-Rays]] and [[gamma ray|Gamma Rays]]'''
|1
|[[Radiation belts]], [[solar radiation]], and bremsstrahlung electrons
|-
|'''[[electron|Electrons]]'''
1.0 MeV 
0.1 MeV
| 
1 
1.08
|Radiation belts
|-
|'''[[proton|Protons]]''' 
100 MeV 
1.5 MeV 
0.1 MeV
| 
1-2 
8.5 
10
|[[Cosmic radiation]], inner-radiation belts, and [[solar radiation]]
|-
|'''[[neutron|Neutrons]]''' 
0.05 ev (thermal) 
1.0 MeV 
10 MeV
| 
2.8 
10.5 
6.4
|Nuclear interactions in the [[sun]]; on Mars, produced when [[cosmic radiation]] interacts with [[regolith]]
|-
|'''[[alpha particles|Alpha Particles]]''' 
5.0 MeV 
1.0 MeV
| 
15 
20
|[[Cosmic radiation]]
|-
|[[Heavy Ions|'''Heavy Ions''']]
|Varies widely
|[[Cosmic radiation]]
|}
(RBE is a measure of the damage done to living tissue, relative to gamma rays)

Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref> Solar radiation includes the same radiation types, but it a higher proportion of protons and its heavy primaries have lower energy levels. The high-energy heavy primaries in cosmic radiation can penetrate materials that effectively block lower-energy radiation<ref name=":1">Rapp D. (2006). Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars. Mars 2:46-71. <nowiki>https://doi.org/10.1555/mars.2006.0004</nowiki></ref>.

==Exposure limits==

===Limits for humans===
Exposure to dangerous levels of radiation causes [[radiation sickness]] and cancer. Any exposure to radiation, no matter how slight, poses some risk. Small dose - small risk of cancer. High dose - high risk of cancer. The average exposure to radiation on Earth due to natural sources is 6.2 mSv per year<ref name=":3">http://www.ans.org/pi/resources/dosechart/msv.php</ref>

Nevertheless, there are defined legal limits for exposure during work for several professional activities, such as for X-ray assistants, airplane personnel, etc. The International Commission on Radiation Protection recommends that occupational (work-related) radiation exposure be limited to 50 millisieverts (mSv) per year, and limited to 100 mSv over any 5-year period<ref>http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103</ref>. NASA's radiation dose limits for astronauts are established in NASA-STD-3001<ref>NASA. (2015). NASA Space Flight Human-System Standard Volume 1, Revision A: Crew Health. Retrieved from https://standards.nasa.gov/standard/nasa/nasa-std-3001-vol-1</ref>.

There is scientific uncertainty surrounding the health hazard from cosmic and solar radiation, because most past research on the health effects of radiation studied only x-rays and gamma rays<ref name=":1" />.

===Limits for plants===

==Martian Environment==

===Effects of the Martian atmosphere===
Most SPE particles will be stopped by the atmosphere before they reach the surface. However, interactions with atmospheric particles can produce neutrons; those neutrons can reach the surface, so the health hazard is not eliminated.

Cosmic radiation protons are likely to penetrate the atmosphere. Cosmic ray heavy ions may fragment in the atmosphere, producing lower-mass ions that can still harm astronauts on the surface.

Mars' thin atmosphere allows more ultraviolet light to reach the surface, compared to Earth. However, habitat structural materials and standard space suits should be sufficient to protect humans from UV radiation.<ref name=":4">Beaty DW, Snook K, Carlton A, Eppler D, Farrell B, Heldmann J,...Zeitlin C, on behalf of the Mars Human Precursor Science Steering Group. (2005). An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Mission to Mars. Available at <nowiki>https://mepag.jpl.nasa.gov/reports/MHP_SSG_(06-02-05).pdf</nowiki></ref>

===Effects of regolith===
When cosmic radiation strikes regolith, it can cause the impacted atoms to emit their own radiation. Surrounding regolith particles absorb much of this radiation, with the exception of neutrons.

Neutrons generated in this way are called albedo neutrons. These neutrons have the potential to add substantially to the radiation dose for astronauts on the surface.<ref name=":4" />

===Dose received by an unprotected human on Mars===

====Cosmic radiation====
The equivalent dose rate from cosmic radiation on Earth's surface at sea level is 0.26 mSv per year<ref name=":3" />. Based on measurements made by the Curiosity rover, the corresponding figure for the surface of Mars is approximately 230 mSv/year<ref name=":0">Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, Ehresmann B, Rafkin S, Eigenbrode JL,...MSL Science Team. (2014). Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover. Science 343(6169). <nowiki>https://doi.org/10.1126/science.1244797</nowiki></ref>. More generally, one model estimated that the dose equivalent rate on the surface of Mars ranges from 156.4 mSv/year (at solar maximum) to 273.8 mSv/year (at solar minimum)<ref name=":2" /><ref>McKenna-Lawlor S, Goncalves P, Keating A, Reitz G, Matthia D. (2012). Overview of Energetic Particle Hazards During Prospective Manned Missions to Mars. Planetary and Space Science. 63: 123-132.</ref>. A 2005 report by the Mars Human Precursor Science Steering Group estimated that (at solar minimum) the dose from cosmic radiation would be 1.2 +/- 0.5 mSv/day; this includes 0.4 +/- 0.4 mSv/day from albedo neutrons.<ref name=":4" />

====Solar Proton Events====
Curiosity also measured the temporary increase in radiation during a single SPE. The results indicate an increase in equivalent dose rate of approximately 25% over a 1-day interval<ref name=":0" />. This figure will vary depending on the intensity of a particular SPE.

==Effect on material==
Radiation can change the properties of [[plastics]] and metals, making them brittle after a period of time.

==Protection==
[[Habitat|Habitats]] should be equipped with a [[radiation shielding]], thick enough to reduce the radiation to a level equal to Earth, that is, almost zero. Best protection may be achieved with houses built in natural [[caves]] or set into cliffs or hillsides.

[[Space suit]]s must be designed with radiation in mind. The suit should provide adequate shielding for the occupant. It may be necessary to design suits with several grades of protection. Suits designed for short-term use can carry lighter shielding which would reduce weight and improve maneuverability.

During severe radiation events, such as [[solar flare|solar flares]], surface [[settlement|settlements]] may use [[storm shelter|storm shelters]] with heavier than normal shielding.

"In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars." <ref name=":2">NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig '' Radiation Shielding Optimization on Mars '', https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf, Apr 2013.</ref>

"An in-situ shielding strategy will also be of little help unless several hundred g/cm2 of regolith is utilized. Such a strategy would probably require large scale excavation making it an unlikely candidate. Instead, the shielding strategy would rely primarily on material optimization. Options, such as replacing aluminum structures with high hydrogen content carbon composites, could be pursued." <ref name=":2" /> This opinion is open to argument as in-situ resources utilization for any type of settlement should make large amounts of regolith available for construction. It mainly is true for the very first level of habitats.

The use of g/cm2 can be translated into an equivalent thickness that depends on the material density. For martian regolith at 2000 kg/m3, a thickness of 1m of regolith is 200 g/cm2. Water (or ice) is 100 g/cm2. So the minimum covering for a long term settlement would be 5m or more. For water, although the radiation absorption is better the density is lower, so about the same thickness would be required for protection (to be discussed)

==References==
<references />

==External links==

*[http://www.ips.gov.au/ IPS:] [http://www.ips.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/guide-to-space-radiation.pdf A Guide to Space Radiation]
*[http://www.niauk.org/radiation-and-safety.html Nuclear Industry Association: Radiation, health and nuclear safety]
*[https://hesperia.gsfc.nasa.gov/sspvse/posters/DF_Smart/poster.pdf The frequency distribution of solar proton events: 5 solar cycles and 45 solar cycles]

[[Category:Radiation Protection]]

Radiation

2019-10-13T19:02:06Z

JimL: Added some information on the radiation environment on the surface of Mars.

[[Image:nuclear_warning_sign.png|right|Nuclear Danger Icon]]
Natural '''Radiation''' on [[Mars]] is much higher compared with [[Earth]]. The thin [[atmosphere]] provides only a small shielding effect against harmful [[solar radiation]] and [[cosmic radiation]]. Mars also lacks the [[magnetosphere]] that protects Earth.

The average natural radiation level on Mars is 24-30 rads or 240-300 mSv per year(needs checking and reference). This is about 40-50 times the average on Earth.

Occasional [[solar flares]] produce particularly high doses. Some Solar Proton Events (SPEs) were observed by [[MARIE]] that were not seen by sensors near Earth due to the fact that SPEs are directional. Astronauts on Mars could be warned of SPEs by sensors closer to the Sun and presumably take shelter during these events. This would imply an [[Early warning system (solar radiation)|Early Warning System]] (possibly a network of sensors in orbit around the sun or a single sensor in [[Lagrangian point]] L1) might be needed to ensure all SPEs threatening Mars were detected early enough.

1 millisievert [mSv] = 0.1 rad [rd]

==Types of Radiation==
Radiation comes in a variety of forms:<ref>http://www.nas.nasa.gov/About/Education/SpaceSettlement/designer/needs.html#SHIELDING</ref>
{| border="1"
|-
!Name
!Relative Biological Effectiveness (RBE)
!Source
|-
|'''[[X-ray|X-Rays]] and [[gamma ray|Gamma Rays]]'''
|1
|[[Radiation belts]], [[solar radiation]], and bremsstrahlung electrons
|-
|'''[[electron|Electrons]]'''
1.0 MeV 
0.1 MeV
| 
1 
1.08
|Radiation belts
|-
|'''[[proton|Protons]]''' 
100 MeV 
1.5 MeV 
0.1 MeV
| 
1-2 
8.5 
10
|[[Cosmic radiation]], inner-radiation belts, and [[solar radiation]]
|-
|'''[[neutron|Neutrons]]''' 
0.05 ev (thermal) 
1.0 MeV 
10 MeV
| 
2.8 
10.5 
6.4
|Nuclear interactions in the [[sun]]; on Mars, produced when [[cosmic radiation]] interacts with [[regolith]]
|-
|'''[[alpha particles|Alpha Particles]]''' 
5.0 MeV 
1.0 MeV
| 
15 
20
|[[Cosmic radiation]]
|-
|[[Heavy Ions|'''Heavy Ions''']]
|Varies widely
|[[Cosmic radiation]]
|}
(RBE is a measure of the damage done to living tissue, relative to gamma rays)

Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref> Solar radiation includes the same radiation types, but it a higher proportion of protons and its heavy primaries have lower energy levels. The high-energy heavy primaries in cosmic radiation can penetrate materials that effectively block lower-energy radiation<ref name=":1">Rapp D. (2006). Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars. Mars 2:46-71. <nowiki>https://doi.org/10.1555/mars.2006.0004</nowiki></ref>.

==Exposure limits==

===Limits for humans===
Exposure to dangerous levels of radiation causes [[radiation sickness]] and cancer. Any exposure to radiation, no matter how slight, poses some risk. Small dose - small risk of cancer. High dose - high risk of cancer. The average exposure to radiation on Earth due to natural sources is 6.2 mSv per year<ref name=":3">http://www.ans.org/pi/resources/dosechart/msv.php</ref>

Nevertheless, there are defined legal limits for exposure during work for several professional activities, such as for X-ray assistants, airplane personnel, etc. The International Commission on Radiation Protection recommends that occupational (work-related) radiation exposure be limited to 50 millisieverts (mSv) per year, and limited to 100 mSv over any 5-year period<ref>http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103</ref>. NASA's radiation dose limits for astronauts are established in NASA-STD-3001<ref>NASA. (2015). NASA Space Flight Human-System Standard Volume 1, Revision A: Crew Health. Retrieved from https://standards.nasa.gov/standard/nasa/nasa-std-3001-vol-1</ref>.

There is scientific uncertainty surrounding the health hazard from cosmic and solar radiation, because most past research on the health effects of radiation studied only x-rays and gamma rays<ref name=":1" />.

===Limits for plants===

==Martian Environment==

=== Effects of the Martian atmosphere ===
Most SPE particles will be stopped by the atmosphere before they reach the surface. However, interactions with atmospheric particles can produce neutrons; those neutrons can reach the surface, so the health hazard is not eliminated.

Cosmic radiation protons are likely to penetrate the atmosphere. Cosmic ray heavy ions may fragment in the atmosphere, producing lower-mass ions that can still harm astronauts on the surface.<ref name=":4">Beaty DW, Snook K, Carlton A, Eppler D, Farrell B, Heldmann J,...Zeitlin C, on behalf of the Mars Human Precursor Science Steering Group. (2005). An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Mission to Mars. Available at <nowiki>https://mepag.jpl.nasa.gov/reports/MHP_SSG_(06-02-05).pdf</nowiki></ref>

=== Effects of regolith ===
When cosmic radiation strikes regolith, it can cause the impacted atoms to emit their own radiation. Surrounding regolith particles absorb much of this radiation, with the exception of neutrons.

Neutrons generated in this way are called albedo neutrons. These neutrons have the potential to add substantially to the radiation dose for astronauts on the surface.<ref name=":4" />

=== Dose received by an unprotected human on Mars ===

==== Cosmic radiation ====
The equivalent dose rate from cosmic radiation on Earth's surface at sea level is 0.26 mSv per year<ref name=":3" />. Based on measurements made by the Curiosity rover, the corresponding figure for the surface of Mars is approximately 230 mSv/year<ref name=":0">Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, Ehresmann B, Rafkin S, Eigenbrode JL,...MSL Science Team. (2014). Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover. Science 343(6169). <nowiki>https://doi.org/10.1126/science.1244797</nowiki></ref>. More generally, one model estimated that the dose equivalent rate on the surface of Mars ranges from 156.4 mSv/year (at solar maximum) to 273.8 mSv/year (at solar minimum)<ref name=":2" /><ref>McKenna-Lawlor S, Goncalves P, Keating A, Reitz G, Matthia D. (2012). Overview of Energetic Particle Hazards During Prospective Manned Missions to Mars. Planetary and Space Science. 63: 123-132.</ref>. A 2005 report by the Mars Human Precursor Science Steering Group estimated that (at solar minimum) the dose from cosmic radiation would be 1.2 +/- 0.5 mSv/day; this includes 0.4 +/- 0.4 mSv/day from albedo neutrons.<ref name=":4" />

==== Solar Proton Events ====
Curiosity also measured the temporary increase in radiation during a single SPE. The results indicate an increase in equivalent dose rate of approximately 25% over a 1-day interval<ref name=":0" />. This figure will vary depending on the intensity of a particular SPE.

==Effect on material==
Radiation can change the properties of [[plastics]] and metals, making them brittle after a period of time.

==Protection==
[[Habitat|Habitats]] should be equipped with a [[radiation shielding]], thick enough to reduce the radiation to a level equal to Earth, that is, almost zero. Best protection may be achieved with houses built in natural [[caves]] or set into cliffs or hillsides.

[[Space suit]]s must be designed with radiation in mind. The suit should provide adequate shielding for the occupant. It may be necessary to design suits with several grades of protection. Suits designed for short-term use can carry lighter shielding which would reduce weight and improve maneuverability.

During severe radiation events, such as [[solar flare|solar flares]], surface [[settlement|settlements]] may use [[storm shelter|storm shelters]] with heavier than normal shielding.

"In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars." <ref name=":2">NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig '' Radiation Shielding Optimization on Mars '', https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf, Apr 2013.</ref>

"An in-situ shielding strategy will also be of little help unless several hundred g/cm2 of regolith is utilized. Such a strategy would probably require large scale excavation making it an unlikely candidate. Instead, the shielding strategy would rely primarily on material optimization. Options, such as replacing aluminum structures with high hydrogen content carbon composites, could be pursued." <ref name=":2" /> This opinion is open to argument as in-situ resources utilization for any type of settlement should make large amounts of regolith available for construction. It mainly is true for the very first level of habitats.

The use of g/cm2 can be translated into an equivalent thickness that depends on the material density. For martian regolith at 2000 kg/m3, a thickness of 1m of regolith is 200 g/cm2. Water (or ice) is 100 g/cm2. So the minimum covering for a long term settlement would be 5m or more. For water, although the radiation absorption is better the density is lower, so about the same thickness would be required for protection (to be discussed)

==References==
<references />

==External links==

*[http://www.ips.gov.au/ IPS:] [http://www.ips.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/guide-to-space-radiation.pdf A Guide to Space Radiation]
*[http://www.niauk.org/radiation-and-safety.html Nuclear Industry Association: Radiation, health and nuclear safety]
*[https://hesperia.gsfc.nasa.gov/sspvse/posters/DF_Smart/poster.pdf The frequency distribution of solar proton events: 5 solar cycles and 45 solar cycles]

[[Category:Radiation Protection]]

Environmental conditions

2019-09-29T17:50:13Z

JimL: Added an external link.

[[Image:126609main_image_feature_400a_ys_full.jpg|thumb|right|300px|The dry and cold surface]]
The '''Environmental conditions''' on [[Mars]] are different from those of [[Earth]]. [[Human]] beings can not live there without technical systems. Unless successful [[terraforming]] can be performed, Martian settlers are bound to artificial [[habitat]]s.

==Temperature==
The temperatures on the Martian surface is much lower than on Earth.

*Average atmosphere temperature: -63 °C
*Diurnal temperature range: -89 °C to -31 °C ([[Viking]] 1 Lander site)
*Minimum: −125 °C near the poles in winter
*Maximum: 20 °C near the equator

==Atmosphere pressure==
The Martian [[atmosphere]] has one hundredth of Earth's atmospheric density and seven thousandths of Earth's atmospheric pressure. The pressure varies considerably from day to day, from season to season, and from place to place on Mars. For practical purposes when designing pressure vessels to maintain life supporting conditions on Mars it is sufficient to estimate the Martian atmospheric pressure as zero.

==Wind==
High wind speeds can occur in large-scale [[Dust storms|storms]] or small [[dust devils]]. There is evidence that wind speeds can exceed 50 meters/second (111 miles/hour). However, the thin atmosphere means that the pressure created by wind is weaker by a factor of 9 than it would be at the same wind speed on Earth. Generally high winds will probably not be a threat to human explorers, with the possible exception of areas where the ground slopes steeply.<ref name=":0">National Research Council. 2002. ''Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface''. Washington, DC: The National Academies Press. <nowiki>https://doi.org/10.17226/10360</nowiki>.</ref>

===Wind speed (Viking Lander sites)===

*Summer: 2-7 m/s
*Fall: 5-10 m/s
*[[Dust storms]]: 17-30 m/s
*[[Dust devils]]: ?

==Dust==
Airborne dust presents potential problems for human explorers. Dust could wear on moving parts if it infiltrates machinery, or could wear away EVA suit seals. Dust that enters a habitat after an EVA could clog air filters. It could accumulate on solar panels, antennas, optical sensors, thermal radiators, or EVA suit visors. The electric charge generated by rover wheels could cause dust adherence that interferes with the drive train.<ref name=":0" />

==Electrostatic Charging==
Human explorers may need to deal with electrostatic shock hazards. On Earth, soil contains enough moisture to conduct electricity, which means electric charge will not build up in grounded objects. Not enough liquid water is present for this effect to occur on Mars. The discharge of built-up static electricity might damage electronics. Equipment and procedures will need to be designed to account for this hazard. Some methods to overcome this sort of problem have been devised at a research station in Antarctica, where the ground contains ice but not liquid (conductive) water.<ref name=":0" />

==Open issues==

*Is there a potential threat from dust devils?

==External Links==

*[http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html Nasa: Mars Fact Sheet]
*[http://www.nasa.gov/worldbook/mars_worldbook.html Nasa: World Book]
*[http://kids.earth.nasa.gov/archive/air_pressure/index.html Nasa: Atmospheric Pressure]
*Beaty, DW, et al. 2005. [https://mepag.jpl.nasa.gov/reports/MHP_SSG_(06-02-05).pdf An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Mission to Mars.]

== References ==
[[Category:Atmospheric Sciences]]
<references />

Radiation

2019-09-23T22:30:18Z

JimL:

[[Image:nuclear_warning_sign.png|right|Nuclear Danger Icon]]
Natural '''Radiation''' on [[Mars]] is much higher compared with [[Earth]]. The thin [[atmosphere]] provides only a small shielding effect against harmful [[solar radiation]] and [[cosmic radiation]]. Mars also lacks the [[magnetosphere]] that protects Earth.

The average natural radiation level on Mars is 24-30 rads or 240-300 mSv per year(needs checking and reference). This is about 40-50 times the average on Earth.

Occasional [[solar flares]] produce particularly high doses. Some Solar Proton Events (SPEs) were observed by [[MARIE]] that were not seen by sensors near Earth due to the fact that SPEs are directional. Astronauts on Mars could be warned of SPEs by sensors closer to the Sun and presumably take shelter during these events. This would imply an [[Early warning system (solar radiation)|Early Warning System]] (possibly a network of sensors in orbit around the sun or a single sensor in [[Lagrangian point]] L1) might be needed to ensure all SPEs threatening Mars were detected early enough.

1 millisievert [mSv] = 0.1 rad [rd]

==Types of Radiation==
Radiation comes in a variety of forms:<ref>http://www.nas.nasa.gov/About/Education/SpaceSettlement/designer/needs.html#SHIELDING</ref>
{| border="1"
|-
!Name
!Relative Biological Effectiveness (RBE)
!Source
|-
|'''[[X-ray|X-Rays]] and [[gamma ray|Gamma Rays]]'''
|1
|[[Radiation belts]], [[solar radiation]], and bremsstrahlung electrons
|-
|'''[[electron|Electrons]]'''
1.0 MeV 
0.1 MeV
| 
1 
1.08
|Radiation belts
|-
|'''[[proton|Protons]]''' 
100 MeV 
1.5 MeV 
0.1 MeV
| 
1-2 
8.5 
10
|[[Cosmic radiation]], inner-radiation belts, and [[solar radiation]]
|-
|'''[[neutron|Neutrons]]''' 
0.05 ev (thermal) 
1.0 MeV 
10 MeV
| 
2.8 
10.5 
6.4
|Nuclear interactions in the [[sun]]; on Mars, produced when [[cosmic radiation]] interacts with [[regolith]]
|-
|'''[[alpha particles|Alpha Particles]]''' 
5.0 MeV 
1.0 MeV
| 
15 
20
|[[Cosmic radiation]]
|-
|[[Heavy Ions|'''Heavy Ions''']]
|Varies widely
|[[Cosmic radiation]]
|}
(RBE is a measure of the damage done to living tissue, relative to gamma rays)

Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref> Solar radiation includes the same radiation types, but it a higher proportion of protons and its heavy primaries have lower energy levels. The high-energy heavy primaries in cosmic radiation can penetrate materials that effectively block lower-energy radiation<ref name=":1">Rapp D. (2006). Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars. Mars 2:46-71. <nowiki>https://doi.org/10.1555/mars.2006.0004</nowiki></ref>.

==Exposure limits==

===Limits for humans===
Exposure to dangerous levels of radiation causes [[radiation sickness]] and cancer. Any exposure to radiation, no matter how slight, poses some risk. Small dose - small risk of cancer. High dose - high risk of cancer. The average exposure to radiation on Earth due to natural sources is 6.2 mSv per year<ref name=":3">http://www.ans.org/pi/resources/dosechart/msv.php</ref>

Nevertheless, there are defined legal limits for exposure during work for several professional activities, such as for X-ray assistants, airplane personnel, etc. The International Commission on Radiation Protection recommends that occupational (work-related) radiation exposure be limited to 50 millisieverts (mSv) per year, and limited to 100 mSv over any 5-year period<ref>http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103</ref>. NASA's radiation dose limits for astronauts are established in NASA-STD-3001<ref>NASA. (2015). NASA Space Flight Human-System Standard Volume 1, Revision A: Crew Health. Retrieved from https://standards.nasa.gov/standard/nasa/nasa-std-3001-vol-1</ref>.

There is scientific uncertainty surrounding the health hazard from cosmic and solar radiation, because most past research on the health effects of radiation studied only x-rays and gamma rays<ref name=":1" />.

===Limits for plants===

==Martian Environment==
The equivalent dose rate from cosmic radiation on Earth's surface at sea level is 0.26 mSv per year<ref name=":3" />. Based on measurements made by the Curiosity rover, the corresponding figure for the surface of Mars is approximately 230 mSv/year<ref name=":0">Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, Ehresmann B, Rafkin S, Eigenbrode JL,...MSL Science Team. (2014). Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover. Science 343(6169). <nowiki>https://doi.org/10.1126/science.1244797</nowiki></ref>. More generally, one model estimated that the dose equivalent rate on the surface of Mars ranges from 156.4 mSv/year (at solar maximum) to 273.8 mSv/year (at solar minimum)<ref name=":2" /><ref>McKenna-Lawlor S, Goncalves P, Keating A, Reitz G, Matthia D. (2012). Overview of Energetic Particle Hazards During Prospective Manned Missions to Mars. Planetary and Space Science. 63: 123-132.</ref>. Curiosity also measured the temporary increase in radiation during a single SPE. The results indicate an increase in equivalent dose rate of approximately 25% over a 1-day interval<ref name=":0" />. This figure will vary depending on the intensity of a particular SPE.

==Effect on material==
Radiation can change the properties of [[plastics]] and metals, making them brittle after a period of time.

==Protection==
[[Habitat|Habitats]] should be equipped with a [[radiation shielding]], thick enough to reduce the radiation to a level equal to Earth, that is, almost zero. Best protection may be achieved with houses built in natural [[caves]] or set into cliffs or hillsides.

[[Space suit]]s must be designed with radiation in mind. The suit should provide adequate shielding for the occupant. It may be necessary to design suits with several grades of protection. Suits designed for short-term use can carry lighter shielding which would reduce weight and improve maneuverability.

During severe radiation events, such as [[solar flare|solar flares]], surface [[settlement|settlements]] may use [[storm shelter|storm shelters]] with heavier than normal shielding.

"In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars." <ref name=":2">NASA, Tony C. Slaba, Christopher J. Mertens, and Steve R. Blattnig '' Radiation Shielding Optimization on Mars '', https://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2013-217983.pdf, Apr 2013.</ref>

"An in-situ shielding strategy will also be of little help unless several hundred g/cm2 of regolith is utilized. Such a strategy would probably require large scale excavation making it an unlikely candidate. Instead, the shielding strategy would rely primarily on material optimization. Options, such as replacing aluminum structures with high hydrogen content carbon composites, could be pursued." <ref name=":2" /> This opinion is open to argument as in-situ resources utilization for any type of settlement should make large amounts of regolith available for construction. It mainly is true for the very first level of habitats.

The use of g/cm2 can be translated into an equivalent thickness that depends on the material density. For martian regolith at 2000 kg/m3, a thickness of 1m of regolith is 200 g/cm2. Water (or ice) is 100 g/cm2. So the minimum covering for a long term settlement would be 5m or more. For water, although the radiation absorption is better the density is lower, so about the same thickness would be required for protection (to be discussed)

==References==
<references />

==External links==

*[http://www.ips.gov.au/ IPS:] [http://www.ips.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/guide-to-space-radiation.pdf A Guide to Space Radiation]
*[http://www.niauk.org/radiation-and-safety.html Nuclear Industry Association: Radiation, health and nuclear safety]
*[https://hesperia.gsfc.nasa.gov/sspvse/posters/DF_Smart/poster.pdf The frequency distribution of solar proton events: 5 solar cycles and 45 solar cycles]

[[Category:Radiation Protection]]

Heavy Ions

2019-09-02T16:44:30Z

JimL:

Heavy ions are charged particles heavier than alpha particles.<ref>Heavy ion. (1998, Jul 20). In ''Encyclopaedia Britannica. <nowiki>https://www.britannica.com/science/heavy-ion</nowiki>''</ref> They constitute 1% of [[cosmic radiation]].<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>

==Exposures==
[[File:Heavy ions in GCR.png|thumb|<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>Abundances and energies of heavy ions in cosmic radiation.|470x470px|alt=]]The left-hand graph shows which elements make up the heavy ions in cosmic radiation. The right-hand graph shows the distribution of energy levels for 4 ions. For example, carbon is one of the more abundant ions in cosmic radiation, and the most likely kinetic energy level for a carbon ion falls between 100 and 1000 MeV.
 
 
 
 
 
 
 

==Health Effects==
[[File:Cucinotta 2009 Fig. 4-3.png|thumb|412x412px|<ref name=":0">Cucinotta FA, Durante M. (2009). Risk of Radiation Carcinogenesis. In ''Human Health and Performance Risks of Space Exploration Missions''. NASA-SP-2009-3405. <nowiki>https://humanresearchroadmap.nasa.gov/Evidence/reports/EvidenceBook.pdf</nowiki></ref>Comparison of the ionization effects on nearby molecules produced by ions with different masses.]]

The effects of high doses of x-rays and gamma rays have been studied thoroughly by analyzing the health of exposed groups.<ref name=":1" /> However, in the case of alpha particles and especially heavy ion radiation, exposures on earth are very rare, and estimates of the risk to astronauts are derived solely from animal model and cell culture studies and application of biophysics principles.<ref name=":0" />

Heavy ions passing through cells transfer more energy into a small volume, compared to other components of cosmic radiation. This concentrated effect can produce qualitatively different types of cell damage.<ref name=":0" />

Linear energy transfer (LET) is a measure of the amount of energy deposited in tissue per unit length of a particle's trajectory.<ref>Wagenaar JD. (1995, Oct 6). Linear Energy Transfer. In ''Radiation Physics Principles'' (Section 7.2.3). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.2/7_2.3.html</nowiki></ref> LET increases as a function of ion charge, and decreases as a function of velocity.<ref>Wagenaar JD. (1995, Oct 6). Stopping Power. In Radiation Physics Principles (Section 7.1.2). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.1/7_1.2.html</nowiki></ref> Experimental irradiation of mouse cell cultures has indicated that heavy ions with an LET greater than 10 keV/μm are more likely to cause irreparable cell damage, compared to protons or alpha particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M-H, Shinn JL, & Badavi FF. (1997, Dec). In JW Wilson, J Miller, A Konradi, & FA Cucinotta, (Eds.), ''Shielding Strategies for Human Space Exploration'' (pp. 109-149). NASA Conference Publication 3360. <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref>

LET has historically been used to estimate relative biological effectiveness (RBE), which is a measure of how harmful radiation is, as compared to the same dose of X-rays or gamma rays. While this estimate might work well for alpha particles (the most common type of high-LET radiation encountered on earth), it might not accurately characterize the damage done by heavy ions. The LET of [[cosmic radiation]] ranges up to around 5,000 KeV/um. RBE is considered to peak at around 100 KeV/um; above that it decreases on account of the smaller number of particles per dose. NASA has adopted a new version of the mathematical formula used to estimate RBE (called the "NASA quality factor"), which is designed to produce more accurate estimates for heavy ions.<ref name=":1">Goodhead DT. (2018, Jun 8). Track Structure and the Quality Factor for Space Radiation Cancer Risk. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20180006105</nowiki></ref>

==Shielding Considerations==
Heavy ions generate secondary radiation due to the very high energy of the particles. This means the thickness of radiation shielding needs to be increased over the requirements of solar storm shelters. This is particularly a consideration for long term settlements, where the accumulation of radiation damage from inadequate shielding might lead to increased cancer rates, neurological, and tissue damage over time.

==References==
<references />

Heavy Ions

2019-09-02T16:43:13Z

JimL:

Heavy ions are charged particles heavier than alpha particles.<ref>Heavy ion. (1998, Jul 20). In ''Encyclopaedia Britannica. <nowiki>https://www.britannica.com/science/heavy-ion</nowiki>''</ref> They constitute 1% of [[cosmic radiation]].<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>

==Exposures==
[[File:Heavy ions in GCR.png|thumb|<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>Abundances and energies of heavy ions in cosmic radiation.|470x470px|alt=]]The left-hand graph shows which elements make up the heavy ions in cosmic radiation. The right-hand graph shows the distribution of energy levels for 4 ions. For example, carbon is one of the more abundant ions in cosmic radiation, and the most likely kinetic energy level for a carbon ion falls between 100 and 1000 MeV.

==Health Effects==
[[File:Cucinotta 2009 Fig. 4-3.png|thumb|412x412px|<ref name=":0">Cucinotta FA, Durante M. (2009). Risk of Radiation Carcinogenesis. In ''Human Health and Performance Risks of Space Exploration Missions''. NASA-SP-2009-3405. <nowiki>https://humanresearchroadmap.nasa.gov/Evidence/reports/EvidenceBook.pdf</nowiki></ref>Comparison of the ionization effects on nearby molecules produced by ions with different masses.]]

The effects of high doses of x-rays and gamma rays have been studied thoroughly by analyzing the health of exposed groups.<ref name=":1" /> However, in the case of alpha particles and especially heavy ion radiation, exposures on earth are very rare, and estimates of the risk to astronauts are derived solely from animal model and cell culture studies and application of biophysics principles.<ref name=":0" />

Heavy ions passing through cells transfer more energy into a small volume, compared to other components of cosmic radiation. This concentrated effect can produce qualitatively different types of cell damage.<ref name=":0" />

Linear energy transfer (LET) is a measure of the amount of energy deposited in tissue per unit length of a particle's trajectory.<ref>Wagenaar JD. (1995, Oct 6). Linear Energy Transfer. In ''Radiation Physics Principles'' (Section 7.2.3). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.2/7_2.3.html</nowiki></ref> LET increases as a function of ion charge, and decreases as a function of velocity.<ref>Wagenaar JD. (1995, Oct 6). Stopping Power. In Radiation Physics Principles (Section 7.1.2). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.1/7_1.2.html</nowiki></ref> Experimental irradiation of mouse cell cultures has indicated that heavy ions with an LET greater than 10 keV/μm are more likely to cause irreparable cell damage, compared to protons or alpha particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M-H, Shinn JL, & Badavi FF. (1997, Dec). In JW Wilson, J Miller, A Konradi, & FA Cucinotta, (Eds.), ''Shielding Strategies for Human Space Exploration'' (pp. 109-149). NASA Conference Publication 3360. <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref>

LET has historically been used to estimate relative biological effectiveness (RBE), which is a measure of how harmful radiation is, as compared to the same dose of X-rays or gamma rays. While this estimate might work well for alpha particles (the most common type of high-LET radiation encountered on earth), it might not accurately characterize the damage done by heavy ions. The LET of [[cosmic radiation]] ranges up to around 5,000 KeV/um. RBE is considered to peak at around 100 KeV/um; above that it decreases on account of the smaller number of particles per dose. NASA has adopted a new version of the mathematical formula used to estimate RBE (called the "NASA quality factor"), which is designed to produce more accurate estimates for heavy ions.<ref name=":1">Goodhead DT. (2018, Jun 8). Track Structure and the Quality Factor for Space Radiation Cancer Risk. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20180006105</nowiki></ref>

==Shielding Considerations==
Heavy ions generate secondary radiation due to the very high energy of the particles. This means the thickness of radiation shielding needs to be increased over the requirements of solar storm shelters. This is particularly a consideration for long term settlements, where the accumulation of radiation damage from inadequate shielding might lead to increased cancer rates, neurological, and tissue damage over time.

==References==
<references />

Heavy Ions

2019-08-26T21:48:47Z

JimL:

Heavy ions are charged particles heavier than alpha particles.<ref>Heavy ion. (1998, Jul 20). In ''Encyclopaedia Britannica. <nowiki>https://www.britannica.com/science/heavy-ion</nowiki>''</ref> They constitute 1% of [[cosmic radiation]].<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>

==Exposures==
[[File:Heavy ions in GCR.png|thumb|<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>Abundances and energies of heavy ions in cosmic radiation.|none|470x470px]]

==Health Effects==
[[File:Cucinotta 2009 Fig. 4-3.png|thumb|412x412px|<ref name=":0">Cucinotta FA, Durante M. (2009). Risk of Radiation Carcinogenesis. In ''Human Health and Performance Risks of Space Exploration Missions''. NASA-SP-2009-3405. <nowiki>https://humanresearchroadmap.nasa.gov/Evidence/reports/EvidenceBook.pdf</nowiki></ref>Comparison of the ionization effects on nearby molecules produced by ions with different masses.]]

The effects of high doses of x-rays and gamma rays have been studied thoroughly by analyzing the health of exposed groups.<ref name=":1" /> However, in the case of alpha particles and especially heavy ion radiation, exposures on earth are very rare, and estimates of the risk to astronauts are derived solely from animal model studies and application of biophysics principles.<ref name=":0" />

Heavy ions passing through cells transfer more energy into a small volume, compared to other components of cosmic radiation. This concentrated effect can produce qualitatively different types of cell damage.<ref name=":0" />

Linear energy transfer (LET) is a measure of the amount of energy deposited in tissue per unit length of a particle's trajectory.<ref>Wagenaar JD. (1995, Oct 6). Linear Energy Transfer. In ''Radiation Physics Principles'' (Section 7.2.3). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.2/7_2.3.html</nowiki></ref> LET increases as a function of ion charge, and decreases as a function of velocity.<ref>Wagenaar JD. (1995, Oct 6). Stopping Power. In Radiation Physics Principles (Section 7.1.2). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.1/7_1.2.html</nowiki></ref> Experimental irradiation of mouse cell cultures has indicated that heavy ions with an LET greater than 10 keV/μm are more likely to cause irreparable cell damage, compared to protons or alpha particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M-H, Shinn JL, & Badavi FF. (1997, Dec). In JW Wilson, J Miller, A Konradi, & FA Cucinotta, (Eds.), ''Shielding Strategies for Human Space Exploration'' (pp. 109-149). NASA Conference Publication 3360. <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref>

LET has historically been used to estimate relative biological effectiveness (RBE), which is a measure of how harmful radiation is, as compared to the same dose of X-rays or gamma rays. While this estimate might work well for alpha particles (the most common type of high-LET radiation encountered on earth), it might not accurately characterize the damage done by heavy ions. The LET of [[cosmic radiation]] ranges up to around 5,000 KeV/um. RBE is considered to peak at around 100 KeV/um; above that it decreases on account of the smaller number of particles per dose. NASA has adopted a new version of the mathematical formula used to estimate RBE (called the "NASA quality factor"), which is designed to produce more accurate estimates for heavy ions.<ref name=":1">Goodhead DT. (2018, Jun 8). Track Structure and the Quality Factor for Space Radiation Cancer Risk. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20180006105</nowiki></ref>

==Shielding Considerations==
Heavy ions generate secondary radiation due to the very high energy of the particles. This means the thickness of radiation shielding needs to be increased over the requirements of solar storm shelters. This is particularly a consideration for long term settlements, where the accumulation of radiation damage from inadequate shielding might lead to increased cancer rates, neurological, and tissue damage over time.

==References==
<references />

Needed Articles

2019-07-08T22:36:56Z

JimL: /* Mars Planetary Science */ Removed Martian Meteorites

This is the global collection of articles that are needed by [[Marspedia]] and shall be a guide for authors, who want to start new articles without knowing which direction to go. Articles with existing links may need expansion.

==Mars Planetary Science==

*List of Mars Calendars
*Observing Mars with a Telescope
*Mars' Orbital Position
*The Goldilocks Zone
*Martian "Geomorphology". What processes have shaped Mars?
*Martian geomorphology: What processes have shaped Mars?
*What are the different topologies on Mars?
*[[Dust storms|Global dust storms]]
*What is the date on Mars? What year/season/month is it?
*Upper atmosphere chemical processes
*[[Gravity|What do the differences in gravity show us?]]
*Reflectance and emission spectroscopy
*Mineral identification from satellite, balloon, and aircraft carried instruments
*Multispectral and thermal infrared imaging
*Geological processes that have shaped Mars
*What minerals could be mined on Mars?
*Mineral spatial distribution
*Subsurface water or ice deposits
*Surface ice at poles
*Surface elevation profiles and maps

==Mars Spacecraft/Robotic Missions==

*Utility of unmanned missions
*Scientific data (collection/transmission/interpretation)
*Follow the water strategy
*Subsurface search strategy
*On-site organic compound detection
*DNA/RNA analysis chips
*Spectrographic imagery
*Multispectral mineral identification
*Multimission timelines
*Mission sequences
*Current and planned instruments
*Orbital vs. lander vs. robotic exploration
*[[Hohmann transfer]] orbits
*[[Aerobraking|Aerocapture orbits]]
*Earth-Mars cyclers
*Chemical propellants
*Nuclear thermal rockets
*[[Ion thruster|Ion propulsion]]
*[[Solar concentrator|Solar mirrors]]
*Solar photoelectric systems
*Wind power (surface and aloft)
*Mars to Earth communication systems
*Equatorial stationary satellites (for communication)
*Aeropositioning satellites (analagous to GPS)
*Miniaturized chemical/molecular identification systems
*Laser communication systems
*Advanced sensing
*AI autonomy
*[[3D Printer|3D printing of complex geometries]]
*Self-replicating machines
*Hybrid machine enhanced biologics
*Exploration missions (list including chronology and instruments)
*Imagery
*Spectroscopy
*Communications
*Lander mission atmospheric seasonal measurements
*Subsurface drilling and chemical analysis
*Degrees of autonomy
*[[Radioisotope Thermoelectric Generator|Solar vs. RTG electrical power sources]]
*Regolith sampling and mineral identification

==Mars Human Exploration==

*[[Transport from Earth to Mars|Transport options]]
*Helicopters
*Mars Direct rockets
*Reverse thrust rockets
*Parachute-assisted descent vehicles
*Methane-oxygen rockets
*Aerology and minerology mapping
*[[EVA Suit|Hybrid hard shell EVA suits]]
*[[EVA Suit|Skin-tight mechanical counterpressure suits]]
*[[Funding]]: International, national, and commercial
*Human factors in crew selection
*[[Radiation|Radiation protection: in transit and for exploration missions]]
*Physical fitness for exploration missions
*Cross training in skill sets
*[[Gravity|Health effects of microgravity]]
*Psychological stressors in transit
*Medical training for exploration teams
*Medical equipment for exploration teams
*Search for life
*Oxygen from CO2 atmosphere
*Organic chemicals and fuel from atmosphere
*Exploration and science in simulated marssuits
*Long-duration missions
*Human factors studies

==Mars Human Settlement==

*[[Settlement facilities]]
*[[Transportation|Inter-settlement transportation]]
*Exploration rovers and rover assistants
*Falcon Heavy for nonhuman payloads
*Big Falcon Rocket for human/nonhuman payloads
*CO2 scrubbers (chemical or biological)
*Biosystems to maintain 02/CO2 ratio
*[[Water Infrastructure|Distribution of water (liquid and ice) on Mars]]
*Impurities in water on Mars
*[[Settlement|Size and specialization of settlements]]
*Manufactured products
*Architecture of buildings
*Wheeled vs. railed surface transportation
*Will Martians eat meat?
*How will the Martians communicate across the planet?
*Total thermal energy need per capita
*Total electrical need per capita
*100% Mars-sourced food production
*Crop choices influenced by ability to thrive in Mars environments
*The listing and timing of materials produced from Mars resources
*Additive manufacture (incl. 3D printing)
*Will individual settlements establish their own societal rules?
*Who owns Mars?
*Mars, LEO, Moon trade triangle
*Increase in pressure needed to allow standing liquid pure water on surface
*Increase in surface temperature to partially melt polar ice caps

==Mars Outreach==

*Mars Society chapters
*Mars Society conferences
*MDRS crews
*Mars Society projects
*Mars Society goals
*[[Mars Foundation]]: About the organization
*[[Hillside Settlement]]
*[[Plains Settlement]]
*About Marspedia
*The Goals of Marspedia

==Mars Arts and Literature==

*chronology of Mars Science Fiction
*lists of Mars Science Fiction by plot-line focus
*list of book sources for Mars facts, history, etc.
*List of Plays
*[[List of Movies]]
*List of Documentaries
*List of TV Series
*List of Music
*List of Computer Games
*List of Board Games
*Accuracy of depiction of Mars in popular culture

Meteorites

2019-07-08T22:31:31Z

JimL: /* See also */ Added internal link

==Definition==

A '''meteorite''' is a body of space debris that enters the atmosphere of a planet and survives the friction with surrounding atmospheric gases to impact the surface energetically. Impact causes planetary [[crater|cratering]], ejecta and dust (forming a layer of [[regolith]] on planets with low geological activity such as Mars). This poses an obvious risk to a Martian [[settlement]], and due to the tenuous [[atmosphere]] of [[Mars]], smaller debris have the greater chance to impact the surface.

==Risk and Mitigations==

Small meteoroids are best handled by a thick layer or [[regolith]]. [[Mars One]] plans to cover the inflatable [[greenhouse]]s with at least 2 meters of it. Most meteoroids are small ones. Also, [[self-healing puncture protection]] for [[space suit]]s and [[house]]s should be installed.

Bigger meteoroids are not so frequent, but they can happen. Meteoroids of the size of a few centimeters are absolutely fatal. Nothings can be done to fend them off. The kinetic [[energy]] is way too much.

And yet, there are possible precautions. One is to modularize the settlement with [[fail-safe|redundant]] facilities on different places. In the case of a hit, the affected module may be destroyed, but the remaining parts allow the surviving settlers to continue the colonization.

For even bigger impacts the needed distances between the redundant modules must be larger. When the settlement reaches 20 persons, a second settlement may be built, dividing the colony in two parts, with a distance of a few hundred meters. Those two settlements should be equipped to work independently from each other, but cables and pipes between them help to support each other in emergency situations, e.g. to supply [[oxygen]] and [[electricity]]. A [[railroad]] between them allows material and person transport.

==Observations of Meteorite Impacts on Mars==

[[Image:Moc_impact.jpg|thumb|right|300px|[[Mars Global Surveyor]] images of the same site in 1999 and 2006 - Impact from meteorite is obvious.]]

On January 9, 2006 the [[Mars Global Surveyor]] MOC science operations team came to the realization that their camera (used primarily to map the Martian surface) may be able to locate and characterize fresh impact craters on the surface of Mars. Such a survey would provide useful information about the current meteorite impact rate. This survey would be the first of its kind ever carried out on a Solar System body (including the Earth-Moon system) due to the unprecedented number of high resolution cameras inserted into Mars orbit.<ref>Go to: [http://wayback.archive.org/ WayBackMachine]. Enter: <nowiki>[http://www.astroengine.net/article.php?id_art=36]</nowiki>. Chose the 9th day of June 2007.</ref>

In results gathered on January 6, 2006, the MOC had acquired a new feature on the Martian surface in [[Arabia Terra]] in one of its images. The feature was circular and very dark. At the time, the camera was capturing images at a resolution of 240 meters/pixel, so there were some ambiguities as to what the blurred feature was. The team began exploring the possible scenarios, but after proving shadows of the two moons, [[Phobos]] and [[Deimos]] were not to blame, they quickly realized that something in the area was new when compared with images taken by [[Mariner 9]] (in 1971) through to the [[Mars Express]] mission (in 2003). There was still the possibility that the dark circular object may have been caused by the removal of [[sand]] and [[dust storms|dust]] due to high winds in the region so better observations had to be carried out.

To increase the resolution in the images, a technique known as Roll-Only Targeted Observation (ROTO) was employed. This massively improved the images for analysis, the new resolution registered at 1.5 meters/pixel allowing the team to see the main impact crater and several smaller craters arcing away from the large dark spot. Another observational technique – compensated Pitch and Roll Observation (cPROTO) – was used to improve the images further until the evidence was indisputable. A fresh impact crater had been discovered.

[[Mars Odyssey]]'s THEMIS instrument and [[Mars Express]]' High Resolution Camera (HRSC) were able to provide supplementary observations of the area to constrain the impact date to some time between November 12, 2004 and January 6, 2006. Since this first discovery in January 6, 2006, another 20 new impact craters have been discovered by the MOC.

==Open issues==

*What is the size and frequency of meteorites on Mars?
*What is the probability for a [[human]] body to be hit by a meteorite on Mars in an hour?

==See also==

*[[Meteors]]
*[[Meteoric iron]]
*[[Martian Meteorite List]]

==References==
<references />

{{SettlementIndex}}

[[category:Mars Meteorites]]

Martian Meteorite List

2019-07-08T22:30:29Z

JimL: Added Date column to table

The below table<ref>Meyer, C., Righter, K. The Martian Meteorite Compendium. Accessed Jan 17, 2019. Available at <nowiki>https://www-curator.jsc.nasa.gov/antmet/mmc/index.cfm</nowiki></ref> lists all known meteorites of Martian origin that have landed on Earth.

{| class="wikitable"
|'''Name'''
|'''Date'''
|'''Mineralogy'''
|-
|Allan Hills 77005
|1977
|Poikilitic shergottite
|-
|Allan Hills 84001
|1984
|orthopyroxenite
|-
|Chassigny
|1815
|Chassignite
|-
|Dar al Gani 476/489/670/735/876/975/1037/1051
|1996-2000
|Olivine-phyric shergottite
|-
|Dhofar 019/1668/1674
|2000/2010
|Olivine-phyric shergottite
|-
|Dhofar 378
|2000
|Fine-grained shergottite
|-
|EET 79001 lithology B
|1980
|Fine-grained shergottite
|-
|Elephant Moraine 79001 lithology A
|1980
|Olivine-phyric shergottite
|-
|Governador Valadares
|1958
|Nakhlite
|-
|Grove Mountains 020090
|2002
|Poikilitic shergottite
|-
|Grove Mountains 99027
|2000
|Poikilitic shergottite
|-
|Jiddat al Harasis 479
|2008
|Diabasic shergottite
|-
|Ksar Ghilane 002
|2010
|Diabasic shergottite
|-
|Lafayette
|1931
|Nakhlite
|-
|Larkman Nunatak 06319/12011
|2007/2012
|Olivine-phyric shergottite
|-
|Larkman Nunatak 12095/12240
|2012
|Olivine-phyric shergottite
|-
|Lewis Cliff 88516
|1988
|Poikilitic shergottite
|-
|Los Angeles
|1980/1999
|Diabasic shergottite
|-
|Miller Range 03346/090030/090032/090136
|2003/2009
|Nakhlite
|-
|Nakhla
|1911
|Nakhlite
|-
|Northwest Africa 10153/10645/10659/10720/11013
|2014
|Nakhlite
|-
|Northwest Africa 1068/1110/1183/1775/2373/2969/
|2001-2004
|Olivine-phyric shergottite
|-
|Northwest Africa 1195
|2002
|Olivine-phyric shergottite
|-
|Northwest Africa 1669
|2001
|Fine-grained shergottite
|-
|Northwest Africa 1950/7721
|2001/2012
|Poikilitic shergottite
|-
|Northwest Africa 2046
|2003
|Olivine-phyric shergottite
|-
|Northwest Africa 2626
|2004
|Olivine-phyric shergottite
|-
|Northwest Africa 2646
|2004
|Poikilitic shergottite
|-
|Northwest Africa 2737
|2000
|Chassignite
|-
|Northwest Africa 2800
|2007
|Diabasic shergottite
|-
|Northwest Africa 2975/2986/2987/4864/4878/4880/4930/ 5214/5219/5313/7182/7890/8116/10068
|2005-2010
|Fine-grained shergottite
|-
|Northwest Africa 2990/5960/6234/6710
|2007-2009
|Olivine-phyric shergottite
|-
|Northwest Africa 3171
|2004
|Fine-grained shergottite
|-
|Northwest Africa 4222
|2006
|Olivine-phyric shergottite
|-
|Northwest Africa 4468
|2006
|Poikilitic shergottite
|-
|Northwest Africa 4480
|2006
|Fine-grained shergottite
|-
|Northwest Africa 4797
|2001
|Poikilitic shergottite
|-
|Northwest Africa 480/1460
|2000-2001
|Diabasic shergottite
|-
|Northwest Africa 4925/4527
|2006
|Olivine-phyric shergottite
|-
|Northwest Africa 5029
|2003
|Diabasic shergottite
|-
|Northwest Africa 5298
|2008
|Diabasic shergottite
|-
|Northwest Africa 5718
|2006
|Fine-grained shergottite
|-
|Northwest Africa 5789
|2009
|Olivine-phyric shergottite
|-
|Northwest Africa 5790/6148
|2008-2009
|Nakhlite
|-
|Northwest Africa 5990
|2009
|Diabasic shergottite
|-
|Northwest Africa 6162
|2010
|Olivine-phyric shergottite
|-
|Northwest Africa 6342
|2010
|Poikilitic shergottite
|-
|Northwest Africa 6963/7258
|2011
|Fine-grained shergottite
|-
|Northwest Africa 7032/7272
|2011
|Gabbroic shergottite
|-
|Northwest Africa 7034/7035/7475/7533/7906/7907/8114/8171/8674/10922/Rabt Sbayta 003
|2011-2016
|Brecciated shergottite
|-
|Northwest Africa 7042
|2011
|Fine-grained shergottite
|-
|Northwest Africa 7257
|2011
|Fine-grained shergottite
|-
|Northwest Africa 7635
|2012
|Diabasic shergottite
|-
|Northwest Africa 8159
|2013
|Fine-grained shergottite
|-
|Northwest Africa 817
|2000
|Nakhlite
|-
|Northwest Africa 856
|2001
|Fine-grained shergottite
|-
|Northwest Africa 8694
|2014
|chassignite
|-
|Northwest Africa 998
|2001
|Nakhlite
|-
|Queen Alexandra Range 94201
|1994
|Diabasic shergottite
|-
|Roberts Massif 04261/04262
|2004
|Poikilitic shergottite
|-
|Sayh al Uhaymir 005/094/008/051/060/090/120/125/130/150/587
|1999-2014
|Olivine-phyric shergottite
|-
|Shergotty
|1865
|Diabasic shergottite
|-
|Tissint
|2011
|Olivine-phyric shergottite
|-
|Yamato 000027/984028/000047/000097
|1998-2000
|Poikilitic shergottite
|-
|Yamato 000593/749/802
|2000
|Nakhlite
|-
|Yamato 793605
|1979
|Poikilitic shergottite
|-
|Yamato 980459/980497
|1998
|Olivine-phyric shergottite
|-
|Yamato 002192/2712
|2000
|Diabasic shergottite
|-
|Zagami
|1962
|Fine-grained shergottite
|-
|Northwest Africa 10134
|2014
|Fine-grained shergottite
|-
|Northwest Africa 10169/10344?
|2015
|Poikilitic shergottite
|-
|Northwest Africa 10171
|2015
|Fine-grained shergottite
|-
|Northwest Africa 10281/10299?
|2014
|Fine-grained shergottite
|-
|Northwest Africa 10414
|2015
|Gabbroic shergottite
|-
|Northwest Africa 10416
|2015
|Olivine-phyric shergottite
|-
|Northwest Africa 10558
|2015
|Diabasic shergottite
|-
|Northwest Africa 10567
|2015
|Gabbroic shergottite
|-
|Northwest Africa 10618
|2016
|Poikilitic shergottite
|-
|Northwest Africa 10693
|2016
|Olivine-phyric shergottite
|-
|Northwest Africa 10697 / 10818?
|2016
|Poikilitic shergottite
|-
|Northwest Africa 10761
|2016
|Gabbroic shergottite
|-
|Northwest Africa 10808
|2016
|Poikilitic shergottite
|-
|Northwest Africa 10961
|2016
|Poikilitic shergottite
|-
|Northwest Africa 11057
|2016
|Diabasic shergottite
|-
|Northwest Africa 11065
|2016
|Poikilitic shergottite
|-
|Northwest Africa 11073
|2016
|Fine-grained shergottite
|-
|Northwest Africa 11115
|2016
|Olivine-phyric shergottite
|-
|Northwest Africa 11251
|2015
|Diabasic shergottite
|-
|Northwest Africa 11255
|2017
|Fine-grained shergottite
|-
|Northwest Africa 11261
|2017
|Poikilitic shergottite
|-
|Northwest Africa 11300
|2017
|Gabbroic shergottite
|-
|Northwest Africa 11339
|2017
|Diabasic shergottite
|-
|Northwest Africa 7320
|2011
|Gabbroic shergottite
|-
|Northwest Africa 7397/7387/7755/7937/8161
|2012-2013
|Poikilitic shergottite
|-
|Northwest Africa 7500
|2012
|Fine-grained shergottite
|-
|Northwest Africa 7944
|2013
|Diabasic shergottite
|-
|Northwest Africa 8637
|2014
|Gabbroic shergottite
|-
|Northwest Africa 8653
|2014
|Fine-grained shergottite
|-
|Northwest Africa 8656/8657/10016/10375/10441/10593/10628/10703/10994/Tindouf 002
|2014
|Diabasic shergottite
|-
|Northwest Africa 8679
|2014
|Fine-grained shergottite
|-
|Northwest Africa 8686
|2014
|Olivine-phyric shergottite
|-
|Northwest Africa 8705
|2014
|Olivine-phyric shergottite
|-
|Northwest Africa 8716 “Jurifiya”
|2014
|Olivine-phyric shergottite
|-
|Northwest Africa 8770
|2014
|Diabasic shergottite
|}

==Additional Resources==
See also the [http://imca.cc/mars/martian-meteorites.htm Martian Meteorites] page on the International Meteorite Collectors Association web site. Their list includes additional entries that are not yet approved by the Meteorical Society.

==References==
<references />
[[Category:Mars Meteorites]]

Talk:Radiation shielding

2019-07-07T17:48:19Z

JimL:

^(M Lamontagne)

I changed the meaning of the magnetic shielding section as it excluded magnetic shielding without sufficient analysis. In particular it didn't refer to minimagnetospheres, and their existence ;on the moon.
The mechanism of a minimagnetosphere may be electric rather than simply magnetic, with particles being ionised by the shield and then deflected by the electrical field potential.
Cosmic :rays might be deflected by very large shields with low densities.

^(JimL)

Some material (the Beer Lamberth law, linear attenuation coefficients, and half value layers) appears to apply only to electromagnetic radiation, so I added a subheading to specify this and allow a comparison of these considerations with particle considerations. If I am wrong about this please correct me.

Radiation shielding

2019-07-07T17:45:46Z

JimL: /* Passive shielding */

Radiation shielding

2019-07-07T17:40:00Z

JimL:

Radiation shielding

2019-07-07T17:39:37Z

JimL: Created new subheadings to cover electromagnetic and particulate radiation separately. Added/moved information under the particulate subheading.

Heavy Ions

2019-06-30T16:40:33Z

JimL: Improved the explanation of linear energy transfer.

Heavy ions are charged particles heavier than alpha particles.<ref>Heavy ion. (1998, Jul 20). In ''Encyclopaedia Britannica. <nowiki>https://www.britannica.com/science/heavy-ion</nowiki>''</ref> They constitute 1% of cosmic radiation.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>

==Exposures==
[[File:Heavy ions in GCR.png|thumb|<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>Abundances and energies of heavy ions in cosmic radiation.|none|470x470px]]

==Health Effects==
[[File:Cucinotta 2009 Fig. 4-3.png|thumb|412x412px|<ref name=":0">Cucinotta FA, Durante M. (2009). Risk of Radiation Carcinogenesis. In ''Human Health and Performance Risks of Space Exploration Missions''. NASA-SP-2009-3405. <nowiki>https://humanresearchroadmap.nasa.gov/Evidence/reports/EvidenceBook.pdf</nowiki></ref>Comparison of the ionization effects on nearby molecules produced by ions with different masses.]]

The effects of high doses of x-rays and gamma rays have been studied thoroughly by analyzing the health of exposed groups.<ref name=":1" /> However, in the case of alpha particles and especially heavy ion radiation, exposures on earth are very rare, and estimates of the risk to astronauts are derived solely from animal model studies and application of biophysics principles.<ref name=":0" />

Heavy ions passing through cells transfer more energy into a small volume, compared to other components of cosmic radiation. This concentrated effect can produce qualitatively different types of cell damage.<ref name=":0" />

Linear energy transfer (LET) is a measure of the amount of energy deposited in tissue per unit length of a particle's trajectory.<ref>Wagenaar JD. (1995, Oct 6). Linear Energy Transfer. In ''Radiation Physics Principles'' (Section 7.2.3). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.2/7_2.3.html</nowiki></ref> LET increases as a function of ion charge, and decreases as a function of velocity.<ref>Wagenaar JD. (1995, Oct 6). Stopping Power. In Radiation Physics Principles (Section 7.1.2). <nowiki>http://www.med.harvard.edu/JPNM/physics/nmltd/radprin/sect7/7.1/7_1.2.html</nowiki></ref> Experimental irradiation of mouse cell cultures has indicated that heavy ions with an LET greater than 10 keV/μm are more likely to cause irreparable cell damage, compared to protons or alpha particles.<ref>Wilson JW, Cucinotta FA, Thibeault SA, Kim M-H, Shinn JL, & Badavi FF. (1997, Dec). In JW Wilson, J Miller, A Konradi, & FA Cucinotta, (Eds.), ''Shielding Strategies for Human Space Exploration'' (pp. 109-149). NASA Conference Publication 3360. <nowiki>http://hdl.handle.net/2060/19980137598</nowiki></ref>

LET has historically been used to estimate relative biological effectiveness (RBE), which is a measure of how harmful radiation is, as compared to the same dose of X-rays or gamma rays. The LET of GCR ranges up to around 5,000 KeV/um. RBE is considered to peak at around 100 KeV/um; above that it decreases on account of the smaller number of particles per dose. While this estimate might work well for alpha particles (the most common type of high-LET radiation encountered on earth), it might not accurately characterize the damage done by heavy ions with the same LET.<ref name=":1">Goodhead DT. (2018, Jun 8). Track Structure and the Quality Factor for Space Radiation Cancer Risk. <nowiki>https://ntrs.nasa.gov/search.jsp?R=20180006105</nowiki></ref>

==Shielding Considerations==
Heavy ions generate secondary radiation due to the very high energy of the particles. This means the thickness of radiation shielding needs to be increased over the requirements of solar storm shelters. This is particularly a consideration for long term settlements, where the accumulation of radiation damage from inadequate shielding might lead to increased cancer rates, neurological, and tissue damage over time.

==References==
<references />

Needed Articles

2019-06-30T15:03:02Z

JimL: Reformatted spacecraft/robotic section to use a flat structure with 1 page per line.

This is the global collection of articles that are needed by [[Marspedia]] and shall be a guide for authors, who want to start new articles without knowing which direction to go.

==Mars Planetary Science==

*List of Mars Calendars
*List of Mars Meteorites on Earth (including Age and Minerology Type)

*Observing Mars with a Telescope
*Mars' Orbital Position
*The Goldilocks Zone
*Phobos
*Deimos
*Telling Time on Mars
*What are the different topologies on Mars?
*Global dust storms
*Dust devils
*Upper atmosphere chemical processes
*What do the differences in gravity show us?
*Reflectance and emission spectroscopy
*Mineral identification from satellite, balloon, and aircraft carried instruments
*Multispectral and thermal infrared imaging
*Geological processes that have shaped Mars
*What minerals could be mined on Mars?
*Mineral spatial distribution
*Subsurface water or ice deposits
*Surface ice at poles
*Glaciers

==Mars Spacecraft/Robotic Missions==

*Utility of unmanned missions
*Scientific data (collection/transmission/interpretation)
*Follow the water strategy
*Subsurface search strategy
*On-site organic compound detection
*DNA/RNA analysis chips
*Spectrographic imagery
*Multispectral mineral identification
*Multimission timelines
*Mission sequences
*Current and planned instruments
*Orbital vs. lander vs. robotic exploration
*Hohmann transfer orbits
*Aerocapture orbits
*Earth-Mars cyclers
*Chemical propellants
*Nuclear thermal rockets
*Ion propulsion
*Nuclear power
*Solar mirrors
*Solar photoelectric systems
*Wind power (surface and aloft)
*Mars to Earth communication systems
*Equitorial stationary satellites (for communication)
*Aeropositioning satellites (analagous to GPS)
*Miniaturized chemical/molecural identification systems
*Advanced sensing
*AI autonomy
*3D printing of complex geometries
*Self-replicating machines
*Hybrid machine enhanced biologics
*Exploration missions (list including chronology and instruments)
*Imagery
*Spectroscopy
*Communications
*Lander mission atmospheric seasonal measurements
*Subsurface drilling and chemical analysis
*Degrees of autonomy
*Solar vs. RTG electrical power sources
*Regolith sampling and mineral identification

==Mars Human Exploration==

*Transport options
*Habitats
*Rovers
*Helicopters
*Mars Direct rockets
*Reverse thrust rockets
*Parachute-assisted descent vehicles
*Methane-oxygen rockets
*Aerology and minerology mapping
*Hybrid hard shell EVA suits
*Skin-tight mechanical counterpressure suits
*Funding: International, national, and commercial
*Human factors in crew selection
*Radiation protection: in transit and for exploration missions
*Physical fitness for exploration missions
*Health effects of microgravity
*Psychological stressors in transit
*Medical training for exploration teams
*Medical equipment for exploration teams
*Water
*Oxygen from CO2 atmosphere
*Organic chemicals and fuel from atmosphere
*Exploration and science in simulated marssuits
*Long-duration missions
*Human factors studies

==Mars Human Settlement==

[[Settlement facilities]]

*Inter-settlement transportation
*Exploration rovers and rover assistants
*Falcon Heavy for nonhuman payloads
*Big Falcon Rocket for human/nonhuman payloads
*CO2 scrubbers (chemical or biological)
*Biosystems to maintain 02/CO2 ratio
*Distribution of water (liquid and ice) on Mars
*Impurities in water on Mars
*Size and specialization of settlements
*Manufactured products
*Architecture of buildings
*Wheeled vs. railed surface transportation
*Will Martians eat meat?
*How will the Martians communicate across the planet?
*Total thermal energy need per capita
*Total electrical need per capita
*100% Mars-sourced food production
*Crop choices influenced by ability to thrive in Mars environments
*The listing and timing of materials produced from Mars resources
*Additive manufacture (incl. 3D printing)
*Will individual settlements establish their own societal rules?
*Who owns Mars?
*Mars, LEO, Moon trade triangle
*Increase in pressure needed to allow standing liquid pure water on surface
*Increase in surface temperature to partially melt polar ice caps

==Mars Outreach==

*Mars Society chapters
*Mars Society conferences
*MDRS crews
*Mars Society projects
*Mars Society goals
*Mars Foundation: About the organization
*Mars Homestead Project history
*Hillside Settlement
*Plains Settlement
*About Marspedia
*The Goals of Marspedia

==Mars Arts and Literature==

*chronology of Mars Science Fiction
*lists of Mars Science Fiction by plot-line focus
*list of book sources for Mars facts, history, etc.
*List of Plays
*List of Movies
*List of Documentaries
*List of TV Series
*List of Science Fiction Movies
*List of Music
*List of Computer Games
*List of Board Games
*Accuracy of depiction of Mars in popular culture

Needed Articles

2019-06-24T20:01:24Z

JimL: /* Mars Spacecraft/Robotic Missions */ Adjusted format for consistency with existing content.