Difference between revisions of "Martian gullies"

From Marspedia
Jump to: navigation, search
(30 intermediate revisions by the same user not shown)
Line 1: Line 1:
 
Martian gullies are narrow channels and their associated downslope sediment deposits, they are found on steep slopes on Mars. They were first discovered on Mars Global Surveyor images especially on the walls of craters. Usually, each gully has a ‘‘alcove’’ at its head, a fan-shaped ''apron'' at its base, and a single thread of incised ''channel'' connecting the two.  The whole gully resembles an hourglass.
 
Martian gullies are narrow channels and their associated downslope sediment deposits, they are found on steep slopes on Mars. They were first discovered on Mars Global Surveyor images especially on the walls of craters. Usually, each gully has a ‘‘alcove’’ at its head, a fan-shaped ''apron'' at its base, and a single thread of incised ''channel'' connecting the two.  The whole gully resembles an hourglass.
 
<ref name="Malin, M. 2000"> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910| </ref>
 
<ref name="Malin, M. 2000"> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910| </ref>
They are estimated to be relatively young because they have few, if any craters.  
+
They are estimated to be relatively young because they have few, if any, craters.  
 +
 
 
[[File:50858 1435gullies.jpg|600pxr|Image of gullies with main parts labeled.  The main parts of a Martian gully are alcove, channel, and apron.  Since there are no craters on this gully, it is thought to be rather young.  Picture was taken by HiRISE under HiWish program.]]
 
[[File:50858 1435gullies.jpg|600pxr|Image of gullies with main parts labeled.  The main parts of a Martian gully are alcove, channel, and apron.  Since there are no craters on this gully, it is thought to be rather young.  Picture was taken by HiRISE under HiWish program.]]
  
 
Most gullies appear 30 degrees poleward in each hemisphere, with greater numbers in the southern hemisphere. Some studies have found that gullies occur on slopes that face all directions.  
 
Most gullies appear 30 degrees poleward in each hemisphere, with greater numbers in the southern hemisphere. Some studies have found that gullies occur on slopes that face all directions.  
 +
 
<ref>cite journal|last1=Edgett|first1=K.|display-authors=etal|date=2003|title=Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit|journal=Lunar Planet. Sci.|volume=34|at=Abstract 1038|url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf|bibcode=2003LPI....34.1038E</ref>  
 
<ref>cite journal|last1=Edgett|first1=K.|display-authors=etal|date=2003|title=Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit|journal=Lunar Planet. Sci.|volume=34|at=Abstract 1038|url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf|bibcode=2003LPI....34.1038E</ref>  
 
Others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S.<ref>Dickson, J; Head, J; Kreslavsky, M (2007). "Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography" (PDF). Icarus. 188: 315–323.</ref>
 
Others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S.<ref>Dickson, J; Head, J; Kreslavsky, M (2007). "Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography" (PDF). Icarus. 188: 315–323.</ref>
 
Although thousands of gullies have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia.
 
Although thousands of gullies have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia.
<refname="2007Icar..188..324H">last1=Heldmann|first1=J|last2=Carlsson|first2=E|last3=Johansson|first3=H|last4=Mellon|first4=M|last5=Toon|first5=O|title=Observations of martian gullies and constraints on potential formation mechanisms. The northern hemisphere|journal=Icarus|volume=188|pages=324–344|date=2007|doi=10.1016/j.icarus.2006.</ref>
+
<ref>name="2007Icar..188..324H">last1=Heldmann|first1=J|last2=Carlsson|first2=E|last3=Johansson|first3=H|last4=Mellon|first4=M|last5=Toon|first5=O|title=Observations of martian gullies and constraints on potential formation mechanisms. The northern hemisphere|journal=Icarus|volume=188|pages=324–344|date=2007|doi=10.1016/j.icarus.2006.</ref>
In the south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra, and along the walls of the Hellas outflow channels.
+
In the south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra, and along the walls of the Hellas outflow channels.<ref>Heldmann, J; Carlsson, E; Johansson, H; Mellon, M; Toon, O (2007). "Observations of martian gullies and constraints on potential formation mechanismsII. The northern hemisphere". Icarus. 188: 324–344.</ref>
<ref>Heldmann, J; Carlsson, E; Johansson, H; Mellon, M; Toon, O (2007). "Observations of martian gullies and constraints on potential formation mechanismsII. The northern hemisphere". Icarus. 188: 324–344.</ref>
 
 
A recent study examined 54,040 CTX images that covered 85% of the Martian surface found 4861 separate gullied landforms (e.g., individual craters, mounds, valleys, etc.), which totaled tens of thousands of individual gullies. This number may represent a fairly accurate census of gullies since it is estimated that CTX can resolve 95% of gullies.
 
A recent study examined 54,040 CTX images that covered 85% of the Martian surface found 4861 separate gullied landforms (e.g., individual craters, mounds, valleys, etc.), which totaled tens of thousands of individual gullies. This number may represent a fairly accurate census of gullies since it is estimated that CTX can resolve 95% of gullies.
 
<ref>Harrison, T., G. Osinski1, and L. Tornabene.  2014. GLOBAL DOCUMENTATION OF GULLIES WITH THE MARS RECONNAISSANCE ORBITER CONTEXT CAMERA (CTX) AND IMPLICATIONS FOR THEIR FORMATION.  45th Lunar and Planetary Science Conference. pdf</ref>
 
<ref>Harrison, T., G. Osinski1, and L. Tornabene.  2014. GLOBAL DOCUMENTATION OF GULLIES WITH THE MARS RECONNAISSANCE ORBITER CONTEXT CAMERA (CTX) AND IMPLICATIONS FOR THEIR FORMATION.  45th Lunar and Planetary Science Conference. pdf</ref>
This article reviews some significant history of the discovery Martian gullies.  On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers think (especially when they were first discovered) that the processes carving the gullies involve liquid water.  Because the gullies are so young, this would suggest that liquid water has been present on Mars in its very recent geological past, consequently added to the possibility of living forms on the present surface.
+
 
 +
On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers think (especially when they were first discovered) that the processes carving gullies involve liquid water.  Because the gullies are so young, this would suggest that liquid water has been present on Mars in its very recent geological past, consequently adding to the possibility of living forms on the present surface.
  
 
After being discovered, many hypotheses were put forward to explain the gullies.
 
After being discovered, many hypotheses were put forward to explain the gullies.
Line 22: Line 24:
 
Moreover, the winding shape of the gullies suggested that the flows were slower than what would be produced in debris flows or eruptions of liquid carbon dioxide. Liquid carbon dioxide would explode out of the ground in the thin Martian atmosphere. Because the liquid carbon dioxide would throw material over 100 meters, the channels should be discontinuous, but they are not.
 
Moreover, the winding shape of the gullies suggested that the flows were slower than what would be produced in debris flows or eruptions of liquid carbon dioxide. Liquid carbon dioxide would explode out of the ground in the thin Martian atmosphere. Because the liquid carbon dioxide would throw material over 100 meters, the channels should be discontinuous, but they are not.
 
<ref name="Heldmann 2004">last1=Heldmann|first1=J|title=Observations of martian gullies and constraints on potential formation mechanisms|journal=Icarus|volume=168|pages=285–304|date=2004|doi=10.1016/j.icarus.2003.11.024|</ref>
 
<ref name="Heldmann 2004">last1=Heldmann|first1=J|title=Observations of martian gullies and constraints on potential formation mechanisms|journal=Icarus|volume=168|pages=285–304|date=2004|doi=10.1016/j.icarus.2003.11.024|</ref>
Eventually, most hypotheses focused on liquid water coming from an aquifer, from melting at the base of old glaciers (or snowpacks), or from the melting of ice in the ground when the climate was warmer.
+
Eventually, most hypotheses focused on liquid water coming from an aquifer, from melting at the base of old glaciers (or snowpacks), or from the melting of ice in the ground when the climate was warmer.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/3060.pdf</ref> <ref>Khuller1, A.,  P. R. Christensen.  2019. EVIDENCE OF WATER-RICH SNOW DEPOSITS WITHIN MARTIAN GULLIES.  50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3060.pdf</ref> <ref> Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304. </ref>  <ref>Forget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK.</ref>
<ref> Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304. </ref>  <ref>Forget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK.</ref>
+
Close-up images with HiRISE showed details that support the idea that a fluid was involved.  Images show that channels formed at various times--smaller channels were found in larger valleys, suggesting that after a valley formed another formed at a later time.  Many cases showed channels took different paths at different times.  Streamlined forms like teardrop-shaped islands were common in some channels. On the Earth, running water is the cause of streamlined forms.<ref>Head, J.,  D. Marchant, M. Kreslavsky.  2008. Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin.  PNAS: 105 (36), 13258–13263.</ref>
Close-up images with HiRISE showed details that support the idea that a fluid was involved.  Images show that channels formed at various times--smaller channels were found in larger valleys, suggesting that after a valley formed another formed at a later time.  Many cases showed channels took different paths at different times.  Streamlined forms like teardrop-shaped islands were common in some channels.
+
 
<ref>Head, J.,  D. Marchant, M. Kreslavsky.  2008. Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin.  PNAS: 105 (36), 13258–13263.</ref>
+
 
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:26420gulliesclose.jpg|Streamlined features in gullies thought to have formed by running water
 
File:26420gulliesclose.jpg|Streamlined features in gullies thought to have formed by running water
 
File:Multiple channels in 21461.jpg| Smaller gullies inside larger ones  Water may have flowed in these gullies more than once.
 
File:Multiple channels in 21461.jpg| Smaller gullies inside larger ones  Water may have flowed in these gullies more than once.
 
File:ESP 039793 1385channeldetails.jpg|Close-up of gullies in crater showing channels within larger valleys and curves in channels.  These characteristics suggest they were made by flowing water.  Location is Eridania quadrangle.
 
File:ESP 039793 1385channeldetails.jpg|Close-up of gullies in crater showing channels within larger valleys and curves in channels.  These characteristics suggest they were made by flowing water.  Location is Eridania quadrangle.
 
</gallery>
 
</gallery>
 +
 
The following group of pictures of gullies illustrates some of the shapes that lead researchers to think that water was involved in creating at least some of the gullies.
 
The following group of pictures of gullies illustrates some of the shapes that lead researchers to think that water was involved in creating at least some of the gullies.
<gallery class="center" widths="190px" heights="180px" >
+
 
 +
 
 +
<gallery class="center" widths="380px" heights="360px">
 
File:45752 1410gullies.jpg|Gullies    The location is the Phaethontis quadrangle.
 
File:45752 1410gullies.jpg|Gullies    The location is the Phaethontis quadrangle.
 
File:46386 1420gullies.jpg|Gullies, as seen by HiRISE  Location is the Phaethontis quadrangle.
 
File:46386 1420gullies.jpg|Gullies, as seen by HiRISE  Location is the Phaethontis quadrangle.
File:ESP 037506 2285gullychannelsclose.jpg|Close-up of gully channels, as seen by HiRISE under HiWish program.  This image shows many streamlined forms and some benches along a channel.  These features suggest formation by running water.  Benches are usually formed when the water level goes down a bit and stays at that level for a time. Picture was taken with HiRISE under HiWish program.  Location is the Mare Acidalium quadrangle.   
+
File:ESP 037506 2285gullychannelsclose.jpg|Close-up of gully channels, as seen by HiRISE under HiWish program.  This image shows many streamlined forms and some benches along a channel.  These features suggest formation by running water.  Benches are usually formed when the water level goes down a bit and stays at that level for a time. Location is the Mare Acidalium quadrangle.   
 
</gallery>
 
</gallery>
  
 
===Aquifers===
 
===Aquifers===
 +
 
One of the earliest ideas attempting to explain gully formation was that water came out of aquifers.  Most of the gully alcove heads occur at the same level, just as one would expect if water came out of aquifers. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies.  Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin.
 
One of the earliest ideas attempting to explain gully formation was that water came out of aquifers.  Most of the gully alcove heads occur at the same level, just as one would expect if water came out of aquifers. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies.  Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin.
 
<ref > Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304.</ref>
 
<ref > Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304.</ref>
Line 45: Line 51:
 
Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.
 
Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.
 
<ref>Harris, A and E. Tuttle. 1990. Geology of National Parks. Kendall/Hunt Publishing Company. Dubuque, Iowa</ref>
 
<ref>Harris, A and E. Tuttle. 1990. Geology of National Parks. Kendall/Hunt Publishing Company. Dubuque, Iowa</ref>
However, the idea that aquifers formed the gullies does not explain the ones found on isolated peaks, like knobs and the central peaks of craters. Also, a type of gully seems to be present on sand dunes.
+
However, the idea that aquifers formed the gullies does not explain the ones found on isolated peaks, like knobs and the central peaks of craters. Also, one kind of gully seems to be present on sand dunes.
 
<ref>Reiss, D, R. Jaumann.  2003.  Recent debris flows on Mars:  Seasonal observations of the Russell Crater dune field.  Geophysical Research letters:  30, 54</ref>  
 
<ref>Reiss, D, R. Jaumann.  2003.  Recent debris flows on Mars:  Seasonal observations of the Russell Crater dune field.  Geophysical Research letters:  30, 54</ref>  
 +
 
[[File:ESP 051770 1345dunegullies.jpg |thumb|300px|left| Gullies on dunes  Some gullies  on sand dunes appear each Martian year.  It is difficult to conceive of an aquifer causing gullies on dunes.]]
 
[[File:ESP 051770 1345dunegullies.jpg |thumb|300px|left| Gullies on dunes  Some gullies  on sand dunes appear each Martian year.  It is difficult to conceive of an aquifer causing gullies on dunes.]]
 +
 +
[[File:ESP 054026 1300gulliesdunes.jpg|thumb|300px|center|Gullies on Dunes in Matara Crater, as seen by HiRISE]]
 +
 
Aquifers need a wide collecting area which is not present on sand dunes or on isolated slopes. Even though most of the original gullies that were seen seemed to come from the same layer in the slope, some exceptions to this pattern have been found.
 
Aquifers need a wide collecting area which is not present on sand dunes or on isolated slopes. Even though most of the original gullies that were seen seemed to come from the same layer in the slope, some exceptions to this pattern have been found.
<ref>Foget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK</ref> Examples of gullies coming from different levels is shown below in the image of Lohse Crater and the image of gullies in Ross Crater.
+
<ref>Foget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK</ref> Examples of gullies coming from different levels are shown below in the image of Lohse Crater and the image of gullies in Ross Crater.
<gallery class="center" widths="190px" heights="180px" >
+
 
 +
 
 +
<gallery class="center" widths="380px" heights="360px">
 
File:Wide view of gully on hill.jpg|CTX image of the next image showing a wide view of the area. Since the hill is isolated it would be difficult for an aquifer to develop. Rectangle shows the approximate location of the next image.
 
File:Wide view of gully on hill.jpg|CTX image of the next image showing a wide view of the area. Since the hill is isolated it would be difficult for an aquifer to develop. Rectangle shows the approximate location of the next image.
 
File:Gully on mound.JPG|Gully on mound as seen by Mars Global Surveyor, under the MOC Public Targeting Program. Images of gullies on isolated peaks, like this one, are difficult to explain with the theory of water coming from aquifers because aquifers need large collecting areas.
 
File:Gully on mound.JPG|Gully on mound as seen by Mars Global Surveyor, under the MOC Public Targeting Program. Images of gullies on isolated peaks, like this one, are difficult to explain with the theory of water coming from aquifers because aquifers need large collecting areas.
Line 58: Line 70:
  
 
===Snowpacks===
 
===Snowpacks===
 +
 
The main basis for the snowpack hypothesis for gully formation is that much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.
 
The main basis for the snowpack hypothesis for gully formation is that much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.
 
<ref>last1=Malin|first1=Michael C.|last2=Edgett|first2=Kenneth S.|title=Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission|journal=Journal of Geophysical Research|volume=106|pages=23429–23570|date=2001|doi=10.1029/2000JE001455</ref> <ref>|pmid=11473309|last1=Mustard|first1=JF|date=2001|pages=411–4|issue=6845|last2=Cooper|volume=412|first2=CD|journal=Nature|last3=Rifkin|first3=MK|title=Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice.|url=http://www.planetary.brown.edu/pdfs/2610.pdf</ref> <ref>last1=Carr|first1=Michael H.|title=Mars Global Surveyor observations of Martian fretted terrain|journal=Journal of Geophysical Research|volume=106|pages=23571–23595|date=2001|doi=10.1029/2000JE001316|</ref>
 
<ref>last1=Malin|first1=Michael C.|last2=Edgett|first2=Kenneth S.|title=Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission|journal=Journal of Geophysical Research|volume=106|pages=23429–23570|date=2001|doi=10.1029/2000JE001455</ref> <ref>|pmid=11473309|last1=Mustard|first1=JF|date=2001|pages=411–4|issue=6845|last2=Cooper|volume=412|first2=CD|journal=Nature|last3=Rifkin|first3=MK|title=Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice.|url=http://www.planetary.brown.edu/pdfs/2610.pdf</ref> <ref>last1=Carr|first1=Michael H.|title=Mars Global Surveyor observations of Martian fretted terrain|journal=Journal of Geophysical Research|volume=106|pages=23571–23595|date=2001|doi=10.1029/2000JE001316|</ref>
This ice-rich mantle, a few yards thick, soothes the land. The mantle may be like a glacier, and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.<ref>http://www.msnbc.msn.com/id/15702457 Martian gullies could be scientific gold mines. Leonard David, 11/13/2006.</ref> <ref name="Head 2008 pmid=18725636|date=2008|last1=Head|first1=JW|last2=Marchant|first2=DR|last3=Kreslavsky|first3=MA|title=Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin|volume=105|issue=36|pages=13258–63|doi=10.1073/pnas.0803760105|pmc=2734344|journal=Proceedings of the National Academy of Sciences of the United States of America|PNAS</ref>
+
This ice-rich mantle, a few yards thick, soothes the land. The mantle may be like a glacier, and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.<ref>http://www.nbcnews.com/id/15702457/ns/technology_and_science-space/t/martian-gullies-could-be-scientific-gold-mines/#.WxVAOUxFzIU</ref> <ref>Head, JW; Marchant, DR; Kreslavsky, MA (2008). "Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin". PNAS. 105 (36): 13258–63.</ref>
 
Indeed, calculations show that a third of a mm of runoff can be produced through the melting of a dusty snowpack each day for 50 days of each Martian year even under current conditions.
 
Indeed, calculations show that a third of a mm of runoff can be produced through the melting of a dusty snowpack each day for 50 days of each Martian year even under current conditions.
 
<ref>last1=Clow|first1=G|title=Generation of liquid water on Mars through the melting of a dusty snowpack|journal=Icarus|volume=72|pages=93–127|date=1987|</ref>  
 
<ref>last1=Clow|first1=G|title=Generation of liquid water on Mars through the melting of a dusty snowpack|journal=Icarus|volume=72|pages=93–127|date=1987|</ref>  
Line 71: Line 84:
 
When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice.  
 
When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice.  
  
<gallery class="center" widths="190px" heights="180px">
+
 
 +
<gallery class="center" widths="380px" heights="360px">
 
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the 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
 
46444 2225mantle.jpg|Mantle
 
46444 2225mantle.jpg|Mantle
Line 82: Line 96:
 
<ref>pages=26695–26712|date=2000|doi=10.1029/2000JE001259|last1=Kreslavsky|volume=105|first1=Mikhail A.|journal=Journal of Geophysical Research|last2=Head|first2=James W.|title=Kilometer-scale roughness of Mars: Results from MOLA data analysis|url=http://www.planetary.brown.edu/pdfs/2447.pdf|</ref> <ref>last1=Hecht|first1=M|title=Metastability of liquid water on Mars|pages=373–386|date=2002|volume=156|doi=10.1006/icar.2001.6794|journal=Icarus|url=http://www.geo.brown.edu/geocourses/geo292/papers/Hecht2002.pdf|format=PDF|</ref>
 
<ref>pages=26695–26712|date=2000|doi=10.1029/2000JE001259|last1=Kreslavsky|volume=105|first1=Mikhail A.|journal=Journal of Geophysical Research|last2=Head|first2=James W.|title=Kilometer-scale roughness of Mars: Results from MOLA data analysis|url=http://www.planetary.brown.edu/pdfs/2447.pdf|</ref> <ref>last1=Hecht|first1=M|title=Metastability of liquid water on Mars|pages=373–386|date=2002|volume=156|doi=10.1006/icar.2001.6794|journal=Icarus|url=http://www.geo.brown.edu/geocourses/geo292/papers/Hecht2002.pdf|format=PDF|</ref>
 
In summary, it is now estimated that during periods of high obliquity, the ice caps will melt causing higher temperature, pressure, and moisture. The moisture will then accumulate as snow in midlatitudes, especially in the more shaded area. At a certain time of the year, sunlight will melt snow with the resulting water producing gullies.
 
In summary, it is now estimated that during periods of high obliquity, the ice caps will melt causing higher temperature, pressure, and moisture. The moisture will then accumulate as snow in midlatitudes, especially in the more shaded area. At a certain time of the year, sunlight will melt snow with the resulting water producing gullies.
 +
 +
A related idea is that buried snow deposits may be uncovered, melt, and help to form gullies.  Evidence for snow deposits being exposed has been observed and reported.</ref>Kuller, A., P. Christensen. 2019. EVIDENCE OF WATER-RICH SNOW DEPOSITS WITHIN MARTIAN GULLIES. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3060.pdf</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/3060.pdf</ref>
  
 
===Melting of ground ice===
 
===Melting of ground ice===
 +
 
The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast.
 
The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast.
 
<ref>last1=Peulvast|first1=J.P.|date=1988|title=Mouvements verticaux et genèse du bourrelet Est-groenlandais. dans la région de Scoresby Sund|journal=Physio Géo|volume=18|pages=87–105|language=French </ref>  
 
<ref>last1=Peulvast|first1=J.P.|date=1988|title=Mouvements verticaux et genèse du bourrelet Est-groenlandais. dans la région de Scoresby Sund|journal=Physio Géo|volume=18|pages=87–105|language=French </ref>  
Line 90: Line 107:
  
 
==Dry ice makes gullies today==
 
==Dry ice makes gullies today==
 +
 +
[[File:ESP 032011 1425newgullies.jpg|600pxr|Changes in gullies, as seen by HiRISE  This shows that gullies are forming today, even though liquid water can not exist on the surface today.]]
 +
 +
Changes in gullies, as seen by HiRISE  This shows that gullies are forming today, even though liquid water can not exist on the surface today
 +
 +
 
As soon as gullies were discovered,
 
As soon as gullies were discovered,
 
<ref name="Malin, M. 2000"> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910| </ref>
 
<ref name="Malin, M. 2000"> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910| </ref>
 
researchers began to image many gullies over and over, looking for possible changes.  By 2006, some changes were found.
 
researchers began to image many gullies over and over, looking for possible changes.  By 2006, some changes were found.
<ref> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | last3 = Posiolova | first3 = L. | last4 = McColley | first4 = S. | last5 = Dobrea | first5 = E. | year = 2006 | title = Present-day impact cratering rate and contemporary gully activity on Mars | url = | journal = Science | volume = 314 | issue = | pages = 1573–1577 | doi=10.1126/science.1135156 | pmid=17158321| </ref>
+
<ref> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | last3 = Posiolova | first3 = L. | last4 = McColley | first4 = S. | last5 = Dobrea | first5 = E. | year = 2006 | title = Present-day impact cratering rate and contemporary gully activity on Mars | url = | journal = Science | volume = 314 | issue = | pages = 1573–1577 | doi=10.1126/science.1135156 | pmid=17158321| </ref>   Liquid water can not exist on Mars today to carve gullies, yet images showed that new gullies were forming.<ref>https://www.uahirise.org/ESP_039701_1095</ref>  <ref>https://www.uahirise.org/ESP_032011_1425</ref>  There must be other mechanisms going on today.
 
Later, analysis revealed that the changes could have occurred by dry granular flows rather than being driven by flowing water.
 
Later, analysis revealed that the changes could have occurred by dry granular flows rather than being driven by flowing water.
 
<ref>| last1 = Kolb | display-authors = et al.  | year = 2010 | title = Investigating gully flow emplacement mechanisms using apex slopes | doi = 10.1016/j.icarus.2010.01.007 | journal = Icarus | volume = 208 | issue = | pages = 132–142 | </ref> <ref> last1 = McEwen | first1 = A. | display-authors = et al.  | year = 2007 | title = A closer look at water-related geological activity on Mars | url = | journal = Science | volume = 317 | issue = | pages = 1706–1708 | </ref> <ref>| last1 = Pelletier | first1 = J. | display-authors = et al.  | year = 2008 | title = Recent bright gully deposits on Mars wet or dry flow? | url = | journal = Geology | volume = 36 | issue = | pages = 211–214 | doi=10.1130/g24346a.1| </ref>
 
<ref>| last1 = Kolb | display-authors = et al.  | year = 2010 | title = Investigating gully flow emplacement mechanisms using apex slopes | doi = 10.1016/j.icarus.2010.01.007 | journal = Icarus | volume = 208 | issue = | pages = 132–142 | </ref> <ref> last1 = McEwen | first1 = A. | display-authors = et al.  | year = 2007 | title = A closer look at water-related geological activity on Mars | url = | journal = Science | volume = 317 | issue = | pages = 1706–1708 | </ref> <ref>| last1 = Pelletier | first1 = J. | display-authors = et al.  | year = 2008 | title = Recent bright gully deposits on Mars wet or dry flow? | url = | journal = Geology | volume = 36 | issue = | pages = 211–214 | doi=10.1130/g24346a.1| </ref>
Line 121: Line 144:
 
<ref>Schorghofer, N., K. Edgett.  2005.  Seasonal surface frost at low latitudes on Mars.  Icarus:  180, 321-334.</ref>
 
<ref>Schorghofer, N., K. Edgett.  2005.  Seasonal surface frost at low latitudes on Mars.  Icarus:  180, 321-334.</ref>
 
It piles up on a frozen permafrost layer that consists of ice-cemented dirt.  When the higher intensity sunlight of spring begins, light penetrates the translucent dry ice layer, consequently warming the ground.  The CO<sub>2</sub> ice absorbs heat and sublimates—that is changes directly from a solid to a gas.  This gas builds up pressure because it is trapped between the ice and the frozen ground.  Eventually, pressure builds up enough to explode through the ice taking with it soil particles.  The dirt particles mix with the pressurized gas and act as a fluid that can flow down the slope and carve gullies.
 
It piles up on a frozen permafrost layer that consists of ice-cemented dirt.  When the higher intensity sunlight of spring begins, light penetrates the translucent dry ice layer, consequently warming the ground.  The CO<sub>2</sub> ice absorbs heat and sublimates—that is changes directly from a solid to a gas.  This gas builds up pressure because it is trapped between the ice and the frozen ground.  Eventually, pressure builds up enough to explode through the ice taking with it soil particles.  The dirt particles mix with the pressurized gas and act as a fluid that can flow down the slope and carve gullies.
On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by the seasonal freezing of [[carbon dioxide]] (CO<sub>2</sub> ice or 'dry ice'), and not by that of liquid water as thought earlier.  So, the current thought is that gullies can be formed today by chunks of dry ice moving down steep slopes today.  Perhaps in the past, water was also involved.
+
On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by the seasonal freezing of [[carbon dioxide]] (CO<sub>2</sub> ice or 'dry ice'), and not by that of liquid water as thought earlier.  So, the current thought is that gullies can be formed today by chunks of dry ice moving down steep slopes today.<ref> Raack, J., et al.  2020.  Present-day gully activity in Sisyphi Cavi, Mars – Flow-like features and block movementsIcarus.  350.  https://doi.org/10.1016/j.icarus.2020.113899. </ref>  Perhaps in the past, water was also involved.<ref name="NASA-20140710">last=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 |date=July 10, 2014 |work=NASA</ref>
<ref name="NASA-20140710">last=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 |date=July 10, 2014 |work=NASA</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> <ref>https://www.uahirise.org/ESP_067299_1435</ref> <ref>Dickson, J., et al.  2021.  THE ELEVATION DISTRIBUTION OF MID-LATITUDE GULLIES ON MARS AS A TEST OF CO2 AND
<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>
+
H2O FORMATION AND MODIFICATION PROCESSES.  52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2426.pdf</ref>
 +
 
 +
In support of water being involved is the fact that many gully alcoves have a greater volume than the aprons.  The material that was in the alcove may have contained much water ice that disappeared into the atmosphere.<ref>Gulick, V. and N. Glines.  2021.  STUDIES OF MARTIAN GULLY SYSTEMS AND THEIR POTENTIAL PALEOENVIRONMENTAL
 +
SETTINGS. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548).  2773.pdf.</ref> <ref>Gulick et al. 2017 LPSC #1970</ref>  Addition evidence that water is involved is that some gullies occur on slopes that are not steep enough for a dry flow, but would be steep enough if water was involved.<ref>Huang, R., et al.  2021.  SLOPE ANALYSIS OF MARTIAN GULLIES IN THREE HIGH-NORTHERN LATITUDE CRATERS.  52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548).  2625.pdf.</ref>
  
 
==References==
 
==References==
 +
 
{{Reflist|colwidth=30em}}
 
{{Reflist|colwidth=30em}}
 +
 
==See also==
 
==See also==
 +
 +
 +
*[[High Resolution Imaging Science Experiment (HiRISE)]]
 
*[[Martian features that are signs of water ice]]
 
*[[Martian features that are signs of water ice]]
*[[Water]]
 
 
*[[Sublimation]]
 
*[[Sublimation]]
 
*[[Sublimation landscapes on Mars]]
 
*[[Sublimation landscapes on Mars]]
 +
*[[Water]]
 
*[[What Mars Actually Looks Like!]]
 
*[[What Mars Actually Looks Like!]]
 +
 
==External links==
 
==External links==
 
* [[https://www.youtube.com/watch?v=mNXBfz1iVzc]] Video demonstrates how dry ice can form gullies on dunes
 
* [[https://www.youtube.com/watch?v=mNXBfz1iVzc]] Video demonstrates how dry ice can form gullies on dunes
 
*[[https://www.youtube.com/watch?v=B1UU8XSMHmM Pictures of gullies on dunes]]
 
*[[https://www.youtube.com/watch?v=B1UU8XSMHmM Pictures of gullies on dunes]]
 
*[[https://www.youtube.com/watch?v=jZpJqlzCRpw Demonstration of dry ice moving down dune ]]
 
*[[https://www.youtube.com/watch?v=jZpJqlzCRpw Demonstration of dry ice moving down dune ]]

Revision as of 11:17, 31 October 2021

Martian gullies are narrow channels and their associated downslope sediment deposits, they are found on steep slopes on Mars. They were first discovered on Mars Global Surveyor images especially on the walls of craters. Usually, each gully has a ‘‘alcove’’ at its head, a fan-shaped apron at its base, and a single thread of incised channel connecting the two. The whole gully resembles an hourglass. [1] They are estimated to be relatively young because they have few, if any, craters.

Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.

Most gullies appear 30 degrees poleward in each hemisphere, with greater numbers in the southern hemisphere. Some studies have found that gullies occur on slopes that face all directions.

[2] Others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S.[3] Although thousands of gullies have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia. [4] In the south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra, and along the walls of the Hellas outflow channels.[5] A recent study examined 54,040 CTX images that covered 85% of the Martian surface found 4861 separate gullied landforms (e.g., individual craters, mounds, valleys, etc.), which totaled tens of thousands of individual gullies. This number may represent a fairly accurate census of gullies since it is estimated that CTX can resolve 95% of gullies. [6]

On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers think (especially when they were first discovered) that the processes carving gullies involve liquid water. Because the gullies are so young, this would suggest that liquid water has been present on Mars in its very recent geological past, consequently adding to the possibility of living forms on the present surface.

After being discovered, many hypotheses were put forward to explain the gullies. [7] However, as in the usual progression of science, some ideas came to be more plausible than others when more observations were made, when other instruments were used, and when statistical analysis was employed. Even though some gullies resembled debris flows on Earth, it was found that many gullies were on slopes that were not steep enough for typical debris flows. Although it was suggested that liquid carbon dioxide could cause gullies, calculations showed that the pressure and temperatures were not suitable for liquid carbon dioxide. [8] [9] [10] Moreover, the winding shape of the gullies suggested that the flows were slower than what would be produced in debris flows or eruptions of liquid carbon dioxide. Liquid carbon dioxide would explode out of the ground in the thin Martian atmosphere. Because the liquid carbon dioxide would throw material over 100 meters, the channels should be discontinuous, but they are not. [11] Eventually, most hypotheses focused on liquid water coming from an aquifer, from melting at the base of old glaciers (or snowpacks), or from the melting of ice in the ground when the climate was warmer.[12] [13] [14] [15] Close-up images with HiRISE showed details that support the idea that a fluid was involved. Images show that channels formed at various times--smaller channels were found in larger valleys, suggesting that after a valley formed another formed at a later time. Many cases showed channels took different paths at different times. Streamlined forms like teardrop-shaped islands were common in some channels. On the Earth, running water is the cause of streamlined forms.[16]


The following group of pictures of gullies illustrates some of the shapes that lead researchers to think that water was involved in creating at least some of the gullies.


Aquifers

One of the earliest ideas attempting to explain gully formation was that water came out of aquifers. Most of the gully alcove heads occur at the same level, just as one would expect if water came out of aquifers. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies. Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin. [17] One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. [18] Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah. [19] However, the idea that aquifers formed the gullies does not explain the ones found on isolated peaks, like knobs and the central peaks of craters. Also, one kind of gully seems to be present on sand dunes. [20]

Gullies on dunes Some gullies on sand dunes appear each Martian year. It is difficult to conceive of an aquifer causing gullies on dunes.
Gullies on Dunes in Matara Crater, as seen by HiRISE

Aquifers need a wide collecting area which is not present on sand dunes or on isolated slopes. Even though most of the original gullies that were seen seemed to come from the same layer in the slope, some exceptions to this pattern have been found. [21] Examples of gullies coming from different levels are shown below in the image of Lohse Crater and the image of gullies in Ross Crater.


Snowpacks

The main basis for the snowpack hypothesis for gully formation is that much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. [22] [23] [24] This ice-rich mantle, a few yards thick, soothes the land. The mantle may be like a glacier, and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.[25] [26] Indeed, calculations show that a third of a mm of runoff can be produced through the melting of a dusty snowpack each day for 50 days of each Martian year even under current conditions. [27] Because there are few craters on this mantle, the mantle is relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE. [28] The ice-rich mantle may be the result of climate changes. [29] Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed with dust. This movement of water could last for several thousand years and create a snow layer of up to around 10 meters thick. [30] [31] When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice.


[32] When the slopes, orientations, and elevations of thousands of gullies were compared, clear patterns emerged from the data. Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow. [33] Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude. For example, Thaumasia quadrangle is heavily cratered with many steep slopes. It is in the right latitude range, but its altitude is so high that there is not enough pressure to keep ice from sublimating (going directly from a solid to a gas); hence it does not have gullies. [34] [35] In summary, it is now estimated that during periods of high obliquity, the ice caps will melt causing higher temperature, pressure, and moisture. The moisture will then accumulate as snow in midlatitudes, especially in the more shaded area. At a certain time of the year, sunlight will melt snow with the resulting water producing gullies.

A related idea is that buried snow deposits may be uncovered, melt, and help to form gullies. Evidence for snow deposits being exposed has been observed and reported.</ref>Kuller, A., P. Christensen. 2019. EVIDENCE OF WATER-RICH SNOW DEPOSITS WITHIN MARTIAN GULLIES. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3060.pdf</ref> [36]

Melting of ground ice

The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast. [37] Since the gullies occur on steep slopes only a small decrease of the shear strength of the soil particles is needed to begin the flow. Small amounts of liquid water from melted ground ice could be enough. [38] [39] [40]

Dry ice makes gullies today

Changes in gullies, as seen by HiRISE This shows that gullies are forming today, even though liquid water can not exist on the surface today.

Changes in gullies, as seen by HiRISE This shows that gullies are forming today, even though liquid water can not exist on the surface today


As soon as gullies were discovered, [1] researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found. [41] Liquid water can not exist on Mars today to carve gullies, yet images showed that new gullies were forming.[42] [43] There must be other mechanisms going on today. Later, analysis revealed that the changes could have occurred by dry granular flows rather than being driven by flowing water. [44] [45] [46] Changes were found in Gasa Crater and other craters. [47] Channels widened by 0.5 to 1 m; meter sized boulders moved; and hundreds of cubic meters of material moved. It was calculated that gullies could be formed under present conditions with as little as 1 event in 50–500 years. Although today there is little liquid water, present geological/climatic processes could still form gullies. [48] Sinuous channels which were thought to need liquid water for their formation have even been seen to form over just a few years when liquid water cannot exist. [49] The timing of gully activity is seasonal and happens during the period when seasonal frost is present and defrosting. [50] Observations with HiRISE show widespread activity in southern hemisphere gullies, especially in those that appear fresh. Significant channel incision and large-scale mass movements have been seen. Neither large amounts of water or great changes in climate were not needed. But, some gullies in the past may have been aided by weather changes that involved larger amounts of water, perhaps from melted snow. [51] Repeated observations, showed that changes occur in the winter and spring. Studies with the High Resolution Imaging Science Experiment (HiRISE) camera on MRO examined gullies at 356 sites, starting in 2006. Thirty-eight of the sites showed active gully formation. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon dioxide frost and temperatures that would not have allowed for liquid water. [52] [53] [54] [55] Some scientists tended to suspect that gullies were formed from carbon dioxide ice (dry ice). When dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes. In some years frost, perhaps as thick as 1 meter, triggers avalanches. This frost contains mostly dry ice, but also has tiny amounts of water ice. [56] These observations support a model in which currently active gully formation is driven mainly by seasonal CO2 frost. [57] [58] Simulations described in a 2015 conference, show that high pressure CO2 gas trapping in the subsurface can cause debris flows. [59] The conditions that can lead to this are found in latitudes where gullies occur.[60] This research was described in a later article entitled, "Formation of gullies on Mars by debris flows triggered by CO2 sublimation." [61] In the model, CO2 ice accumulates in the cold winter. [62] It piles up on a frozen permafrost layer that consists of ice-cemented dirt. When the higher intensity sunlight of spring begins, light penetrates the translucent dry ice layer, consequently warming the ground. The CO2 ice absorbs heat and sublimates—that is changes directly from a solid to a gas. This gas builds up pressure because it is trapped between the ice and the frozen ground. Eventually, pressure builds up enough to explode through the ice taking with it soil particles. The dirt particles mix with the pressurized gas and act as a fluid that can flow down the slope and carve gullies. On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by the seasonal freezing of carbon dioxide (CO2 ice or 'dry ice'), and not by that of liquid water as thought earlier. So, the current thought is that gullies can be formed today by chunks of dry ice moving down steep slopes today.[63] Perhaps in the past, water was also involved.[64] [65] [66] [67] [68]

In support of water being involved is the fact that many gully alcoves have a greater volume than the aprons. The material that was in the alcove may have contained much water ice that disappeared into the atmosphere.[69] [70] Addition evidence that water is involved is that some gullies occur on slopes that are not steep enough for a dry flow, but would be steep enough if water was involved.[71]

References

  1. 1.0 1.1 last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910|
  2. cite journal|last1=Edgett|first1=K.|display-authors=etal|date=2003|title=Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit|journal=Lunar Planet. Sci.|volume=34|at=Abstract 1038|url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf%7Cbibcode=2003LPI....34.1038E
  3. Dickson, J; Head, J; Kreslavsky, M (2007). "Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography" (PDF). Icarus. 188: 315–323.
  4. name="2007Icar..188..324H">last1=Heldmann|first1=J|last2=Carlsson|first2=E|last3=Johansson|first3=H|last4=Mellon|first4=M|last5=Toon|first5=O|title=Observations of martian gullies and constraints on potential formation mechanisms. The northern hemisphere|journal=Icarus|volume=188|pages=324–344|date=2007|doi=10.1016/j.icarus.2006.
  5. Heldmann, J; Carlsson, E; Johansson, H; Mellon, M; Toon, O (2007). "Observations of martian gullies and constraints on potential formation mechanismsII. The northern hemisphere". Icarus. 188: 324–344.
  6. Harrison, T., G. Osinski1, and L. Tornabene. 2014. GLOBAL DOCUMENTATION OF GULLIES WITH THE MARS RECONNAISSANCE ORBITER CONTEXT CAMERA (CTX) AND IMPLICATIONS FOR THEIR FORMATION. 45th Lunar and Planetary Science Conference. pdf
  7. http://www.psrd.hawaii.edu/Aug03/MartianGullies.html
  8. Musselwhite, C., et al. 2001. Liquid CO2 Breakout and the formation of recent small gullies on Mars. Lunar and Planetary Science XXXII. 1030.pdf
  9. Stewart, S. 2001. Lunar and Planetary Science XXXII. 17820.pdf
  10. Stewart, S. 2001. Surface runoff features on Mars: Testing the carbon dioxide formation hypothesis. Lunar and Planetary Science XXXII. 1780.pdf
  11. last1=Heldmann|first1=J|title=Observations of martian gullies and constraints on potential formation mechanisms|journal=Icarus|volume=168|pages=285–304|date=2004|doi=10.1016/j.icarus.2003.11.024|
  12. https://www.hou.usra.edu/meetings/lpsc2019/pdf/3060.pdf
  13. Khuller1, A., P. R. Christensen. 2019. EVIDENCE OF WATER-RICH SNOW DEPOSITS WITHIN MARTIAN GULLIES. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3060.pdf
  14. Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304.
  15. Forget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK.
  16. Head, J., D. Marchant, M. Kreslavsky. 2008. Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin. PNAS: 105 (36), 13258–13263.
  17. Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304.
  18. http://www.space.com/scienceastronomy/mars_aquifer_041112.html Mars Gullies Likely Formed By Underground Aquifers. Leonard David, 12 November 2004 (Space.com)
  19. Harris, A and E. Tuttle. 1990. Geology of National Parks. Kendall/Hunt Publishing Company. Dubuque, Iowa
  20. Reiss, D, R. Jaumann. 2003. Recent debris flows on Mars: Seasonal observations of the Russell Crater dune field. Geophysical Research letters: 30, 54
  21. Foget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK
  22. last1=Malin|first1=Michael C.|last2=Edgett|first2=Kenneth S.|title=Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission|journal=Journal of Geophysical Research|volume=106|pages=23429–23570|date=2001|doi=10.1029/2000JE001455
  23. |pmid=11473309|last1=Mustard|first1=JF|date=2001|pages=411–4|issue=6845|last2=Cooper|volume=412|first2=CD|journal=Nature|last3=Rifkin|first3=MK|title=Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice.|url=http://www.planetary.brown.edu/pdfs/2610.pdf
  24. last1=Carr|first1=Michael H.|title=Mars Global Surveyor observations of Martian fretted terrain|journal=Journal of Geophysical Research|volume=106|pages=23571–23595|date=2001|doi=10.1029/2000JE001316|
  25. http://www.nbcnews.com/id/15702457/ns/technology_and_science-space/t/martian-gullies-could-be-scientific-gold-mines/#.WxVAOUxFzIU
  26. Head, JW; Marchant, DR; Kreslavsky, MA (2008). "Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin". PNAS. 105 (36): 13258–63.
  27. last1=Clow|first1=G|title=Generation of liquid water on Mars through the melting of a dusty snowpack|journal=Icarus|volume=72|pages=93–127|date=1987|
  28. last1=Christensen|first1=PR|title=Formation of recent martian gullies through melting of extensive water-rich snow deposits.|journal=Nature|volume=422|issue=6927|pages=45–8|date=2003|pmid=12594459|doi=10.1038/nature01436
  29. http://news.nationalgeographic.com/news/2008/03/080319-mars-gullies_2.html Melting Snow Created Mars Gullies, Expert Says
  30. last1=Jakosky|first1=Bruce M.|last2=Carr|first2=Michael H.|title=Possible precipitation of ice at low latitudes of Mars during periods of high obliquity|journal=Nature|volume=315|pages=559–561|date=1985|doi=10.1038/315559a0|issue=6020
  31. |last1=Jakosky|first1=Bruce M.|last2=Henderson|first2=Bradley G.|last3=Mellon|first3=Michael T.|title=Chaotic obliquity and the nature of the Martian climate|journal=Journal of Geophysical Research|volume=100|pages=1579–1584|date=1995|
  32. author=MLA NASA/Jet Propulsion Laboratory|date=December 18, 2003|title=Mars May Be Emerging From An Ice Age|work=ScienceDaily|accessdate=February 19, 2009|url=https://www.sciencedaily.com/releases/2003/12/
  33. last1=Dickson|first1=J|last2=Head|first2=J|last3=Kreslavsky|first3=M|title=Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography|doi=10.1016/j.icarus.2006.11.020|url=http://www.planetary.brown.edu/pdfs/3138.pdf%7Cdate=2007%7Cpages=315–323%7Cvolume=188%7Cjournal=Icarus%7Cformat=PDF
  34. pages=26695–26712|date=2000|doi=10.1029/2000JE001259|last1=Kreslavsky|volume=105|first1=Mikhail A.|journal=Journal of Geophysical Research|last2=Head|first2=James W.|title=Kilometer-scale roughness of Mars: Results from MOLA data analysis|url=http://www.planetary.brown.edu/pdfs/2447.pdf%7C
  35. last1=Hecht|first1=M|title=Metastability of liquid water on Mars|pages=373–386|date=2002|volume=156|doi=10.1006/icar.2001.6794|journal=Icarus|url=http://www.geo.brown.edu/geocourses/geo292/papers/Hecht2002.pdf%7Cformat=PDF%7C
  36. https://www.hou.usra.edu/meetings/lpsc2019/pdf/3060.pdf
  37. last1=Peulvast|first1=J.P.|date=1988|title=Mouvements verticaux et genèse du bourrelet Est-groenlandais. dans la région de Scoresby Sund|journal=Physio Géo|volume=18|pages=87–105|language=French
  38. author1=Jouannic G. |author2=J. Gargani |author3=S. Conway |author4=F. Costard |author5=M. Balme |author6=M. Patel |author7=M. Massé |author8=C. Marmo |author9=V. Jomelli |author10=G. Ori |date=2015|title= Laboratory simulation of debris flows over a sand dune : Insights into gully-formation (Mars)|journal=Geomorphology|volume=231|pages=101–115|url=http://www.sciencedirect.com/science/article/pii/S0169555X14005972%7Cdoi=10.1016/j.geomorph.2014.12.007%7C
  39. last1=Costard|first1=F.|display-authors=etal|date=2001|title=Debris Flows on Mars: Analogy with Terrestrial Periglacial Environment and Climatic Implications|journal=Lunar and Planetary Science|volume=XXXII||url=http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1534.pdf%7Cformat=PDF
  40. {{cite web |url=http://www.spaceref.com/16090/news/viewpr.html?pid=7124 |title=Archived copy |accessdate=2011-03-10 |deadurl=yes |archiveurl=https://archive.is/20120910131532/http://www.spaceref.com/16090/news/viewpr.html?pid=7124 |
  41. last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | last3 = Posiolova | first3 = L. | last4 = McColley | first4 = S. | last5 = Dobrea | first5 = E. | year = 2006 | title = Present-day impact cratering rate and contemporary gully activity on Mars | url = | journal = Science | volume = 314 | issue = | pages = 1573–1577 | doi=10.1126/science.1135156 | pmid=17158321|
  42. https://www.uahirise.org/ESP_039701_1095
  43. https://www.uahirise.org/ESP_032011_1425
  44. | last1 = Kolb | display-authors = et al. | year = 2010 | title = Investigating gully flow emplacement mechanisms using apex slopes | doi = 10.1016/j.icarus.2010.01.007 | journal = Icarus | volume = 208 | issue = | pages = 132–142 |
  45. last1 = McEwen | first1 = A. | display-authors = et al. | year = 2007 | title = A closer look at water-related geological activity on Mars | url = | journal = Science | volume = 317 | issue = | pages = 1706–1708 |
  46. | last1 = Pelletier | first1 = J. | display-authors = et al. | year = 2008 | title = Recent bright gully deposits on Mars wet or dry flow? | url = | journal = Geology | volume = 36 | issue = | pages = 211–214 | doi=10.1130/g24346a.1|
  47. NASA/Jet Propulsion Laboratory. "NASA orbiter finds new gully channel on Mars." ScienceDaily. ScienceDaily, 22 March 2014. www.sciencedaily.com/releases/2014/03/140322094409.htm
  48. Dundas, C., S. Diniega, and A. McEwen. 2014. LONG-TERM MONITORING OF MARTIAN GULLY ACTIVITY WITH HIRISE. 45th Lunar and Planetary Science Conference. 2204.pdf
  49. Dundas, C. et al. 2016. HOW WET IS RECENT MARS? INSIGHTS FROM GULLIES AND RSL. 47th Lunar and Planetary Science Conference (2016) 2327.pdf.
  50. Vincendon, M. 2015. JGR:120, 1859–1879.
  51. Dundas, C., S. Diniega, C. Hansen, S. Byrne, A. McEwen. 2012. Seasonal activity and morphological changes in martian gullies. Icarus, 220. 124–143.
  52. http://www.jpl.nasa.gov/news/news.php?release=2014-226
  53. http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158/
  54. http://hirise.lpl.arizona.edu/ESP_032078_1420
  55. http://www.space.com/26534-mars-gullies-dry-ice.html
  56. http://spaceref.com/mars/frosty-gullies-on-mars.html
  57. Dundas, C., S. Diniega, A. McEwen. 2015. Long-term monitoring of martian gully formation and evolution with MRO/HiRISE. Icarus: 251, 244–263
  58. last1 = Raack | first1 = J. | display-authors = etal | year = 2015 | title = Present-day seasonal gully activity in a south polar pit (Sisyphi Cavi) on Mars| url = | journal = Icarus | volume = 251 | issue = | pages = 226–243 | doi=10.1016/j.icarus.2014.03.040 |
  59. http://www.uahirise.org/ESP_044327_1375
  60. C. Pilorget, C., F. Forget. 2015. "CO2 Driven Formation of Gullies on Mars." 46th Lunar and Planetary Science Conference. 2471.pdf
  61. | last1 = 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 |
  62. Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.
  63. Raack, J., et al. 2020. Present-day gully activity in Sisyphi Cavi, Mars – Flow-like features and block movements. Icarus. 350. https://doi.org/10.1016/j.icarus.2020.113899.
  64. last=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 |date=July 10, 2014 |work=NASA
  65. 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
  66. http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158
  67. https://www.uahirise.org/ESP_067299_1435
  68. Dickson, J., et al. 2021. THE ELEVATION DISTRIBUTION OF MID-LATITUDE GULLIES ON MARS AS A TEST OF CO2 AND H2O FORMATION AND MODIFICATION PROCESSES. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2426.pdf
  69. Gulick, V. and N. Glines. 2021. STUDIES OF MARTIAN GULLY SYSTEMS AND THEIR POTENTIAL PALEOENVIRONMENTAL SETTINGS. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 2773.pdf.
  70. Gulick et al. 2017 LPSC #1970
  71. Huang, R., et al. 2021. SLOPE ANALYSIS OF MARTIAN GULLIES IN THREE HIGH-NORTHERN LATITUDE CRATERS. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 2625.pdf.

See also

External links