Atmosphere - Revision history

RichardWSmith: /* Mesoscale Atmospheric Behaviour */ spelling

2025-11-18T19:39:42Z

Mesoscale Atmospheric Behaviour: spelling

RichardWSmith: /* Color of the Sky */ changed word choice.

2025-11-18T19:32:50Z

Color of the Sky: changed word choice.

RichardWSmith: Added link

2025-08-03T16:59:45Z

Added link

RichardWSmith: /* Vertical Organization */ Reworded sentence to make it less repetitive.

2024-12-08T21:13:31Z

Vertical Organization: Reworded sentence to make it less repetitive.

RichardWSmith: Added new section on the vertical organization of the Martian atmosphere.

2024-12-07T10:53:39Z

Added new section on the vertical organization of the Martian atmosphere.

RichardWSmith: /* PhotoChemistry in the Martian Atmosphere */ grammar

2024-11-29T03:11:54Z

PhotoChemistry in the Martian Atmosphere: grammar

RichardWSmith: Added link.

2024-11-29T03:09:33Z

Added link.

RichardWSmith: New section on photochemistry.

2024-11-29T03:06:30Z

New section on photochemistry.

RichardWSmith: /* Carbon Dioxide Atmospheric Effects */ Organized new section into sub-sections.

2024-11-26T01:41:07Z

Carbon Dioxide Atmospheric Effects: Organized new section into sub-sections.

RichardWSmith: /* Carbon Dioxide Atmospheric Effects */

2024-11-26T01:26:51Z

Carbon Dioxide Atmospheric Effects

@@ Line 129: / Line 129: @@
 -- Martian dust storms can be small and local, large, or planet wide.  Mesoscale studies have shown that tho they may be global in extent the vast majority of the dust are lifted from fairly small lifting centres.  The largest storms seem to occur when thermal tides (described below), interact with baroclinic wind fronts carrying plenty of dust.  The turbulence caused when the 'tidal gate' is opened allows what would be a regional dust storm to go planet wide.  This 'tidal gate' may only be open for as little as 11 hours.
--- Gavity Waves (described below) have been observed on Mars, and are thought to contribute to the equatorial CO2 clouds as well as other processes.  They are a Mesoscale behaviour.
+-- Gravity Waves (described below) have been observed on Mars, and are thought to contribute to the equatorial CO2 clouds as well as other processes.  They are a Mesoscale behaviour.
 -- Carbon dioxide is the majority gas in Mars' atmosphere, and in polar winter it can condense out forming huge clouds, fogs, and carbon dioxide snow.  This causes Mesoscale behaviour totally unlike anything seen on Earth.  Gases such as Neon can be locally enriched (changing the atmospheric density), the energy released as the CO2 condenses and freezes causes localized updrafts in the area of generally settling air.  More study of these complex processes would be welcome.

@@ Line 77: / Line 77: @@
 ==Color of the Sky==
-The color of the sky is usually reddish or salmon coloured due to the dust suspended in it.  However, at times when the sky is very dust free, it can be blue, for the same reason that the Earth's sky is blue.  (Red light is scattered more, so more blue light makes it down to the ground.) The sky may also be blue at sunset due to the fine dust scattering the other colors, leaving a blue color near the sun.
+The color of the sky is almost always reddish or salmon coloured due to the dust suspended in it.  However, at times when the sky is very dust free, it can be blue, for the same reason that the Earth's sky is blue.  (Red light is scattered more, so more blue light makes it down to the ground.) The sky may also be blue at sunset due to the fine dust scattering the other colors, leaving a blue color near the sun.
 ==Clouds (Carbon Dioxide)==

@@ Line 2: / Line 2: @@
 The '''Atmosphere''' of [[Mars]] is not breathable. The pressure is too low, and there is too little [[oxygen]]. And yet, it gives Mars something that makes it the most habitable of all planets in our [[solar system]], except [[Earth]] of course. It provides valuable [[:category:chemistry|chemicals]], and it forms a visible sky, mostly from dispersed dust.  Also note that it protects from lower energy radiation particles, stopping 1.58% of the radiation from space, even though it has only 0.6% of the Earth's air pressure.
-Mars at one time had a much thicker atmosphere, see [[Atmospheric loss]] for what happened to this thick atmosphere.
+Mars at one time had a much thicker atmosphere, see [[Ancient Atmosphere]] & [[Atmospheric loss]] for what happened to this thick atmosphere.
 ==Composition (gaseous parts)==

@@ Line 63: / Line 63: @@
 Imbedded within the Thermosphere is the ionosphere, a region of thin plasma.  Most of this plasma is formed by Extreme UltraViolet light (EUV) ionizing the air.  EUV is the most energetic UV light, shading into soft X-rays.
-Above the Homopause, the gas molecules take long paths with few collisions.  They start to sort themselves by the types of gas (so carbon monoxide (CO) being lighter than carbon dioxide (CO<sub>2</sub>) becomes more common at higher attitudes.  The different gases start to sort themselves by molecular mass.
+Above the Homopause, the gas molecules take long paths with few collisions.  They start to sort themselves by the types of gas (so carbon monoxide (CO) being lighter than carbon dioxide (CO<sub>2</sub>) becomes more common at higher attitudes.  Thus, lighter gases (ones with low molecular mass) such as atomic oxygen sort themselves higher.
 ==Air Temperature==

← Older revision		Revision as of 10:53, 7 December 2024
Line 44:		Line 44:

	The scale height of Mars (the relationship that says how quickly the atmosphere thins as you rise) is 10km. Thus every km you rise above the surface, the air pressure drops by about 10%. (This relationship works best near the ground, at very high altitudes, the atmosphere thins more slowly.)		The scale height of Mars (the relationship that says how quickly the atmosphere thins as you rise) is 10km. Thus every km you rise above the surface, the air pressure drops by about 10%. (This relationship works best near the ground, at very high altitudes, the atmosphere thins more slowly.)
		+
		+	==Vertical Organization==
		+	Scientists have organized the Martian atmosphere into the following regions, starting from the ground and moving up:
		+	*Troposphere (~0 to ~50 km). Tropopause is at ~40 to 50 km.
		+	*Mesosphere (~50 to ~100 km). Mesopause is about ~120 km.
		+	*Thermosphere (~100 to ~200 km). Homopause is at about 125 km.
		+	*Exosphere. (Higher than ~200 km) Thins out to space.
		+
		+	These names are analogous to Earth, except with no ozone layer, Mars has no stratosphere. (The stratosphere of the Earth's atmosphere is strongly warmed by the ozone layer stopping UV light and warming.)
		+
		+	Other scientists prefer to use the more neutral names:
		+	*Lower Atmosphere 0 to 50 km
		+	*Middle Atmosphere 50 to 100 km
		+	*Upper atmosphere more than 100 km.
		+
		+	When Mars is dusty, the [[Dust]] absorbs more solar heat and warms the air. This causes the upper edge of the Martian atmosphere to expand by ~25 km, and these divisions move higher.
		+
		+	Imbedded within the Thermosphere is the ionosphere, a region of thin plasma. Most of this plasma is formed by Extreme UltraViolet light (EUV) ionizing the air. EUV is the most energetic UV light, shading into soft X-rays.
		+
		+	Above the Homopause, the gas molecules take long paths with few collisions. They start to sort themselves by the types of gas (so carbon monoxide (CO) being lighter than carbon dioxide (CO<sub>2</sub>) becomes more common at higher attitudes. The different gases start to sort themselves by molecular mass.

	==Air Temperature==		==Air Temperature==

@@ Line 278: / Line 278: @@
 An unusual land form are the Martian [[Black spiders]] or 'araneiforms'.  These are formed by the movement of dust under a slab of solid carbon dioxide, breaking free thru cracks in the ice.  They are associated with fans of dust.
-==PhotoChemistry in the Martian Atmosphere==
+==Photo-Chemistry in the Martian Atmosphere==
 See this link: [[Photochemistry]] for more information. But in short, high energy photons from the sun (mostly [[Ultraviolet]] light, break up atoms in the Martian atmosphere.  The most important major gases are CO<sub>2</sub> and H<sub>2</sub>O.  These form a variety of short lived, unstable molecular species, including: OH, HO<sub>2</sub>, hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), atomic hydrogen, atomic oxygen, [[Ozone]] (O<sub>3</sub>), and others.

@@ Line 277: / Line 277: @@
 ===Fans and Spiders===
 An unusual land form are the Martian [[Black spiders]] or 'araneiforms'.  These are formed by the movement of dust under a slab of solid carbon dioxide, breaking free thru cracks in the ice.  They are associated with fans of dust.
 ==Bibliography==

@@ Line 249: / Line 249: @@
 Mars is the only world where a major part of its atmosphere freezes in winter, and one of only 3 worlds where the major gas of the atmosphere forms clouds.  About 30% of the Martian atmosphere freezes out during the southern polar night, which has major consequences for the dynamics of the atmosphere.  This can cause a six fold concentration of non-condensable gasses (primarily N<sub>2</sub>, Ar, & CO).
 Carbon dioxide (CO<sub>2</sub>) ice is white, but when mixed with dust or water ice is darker.  Also its albedo changes if it is in the form of frost or snow (brighter), or as a solid mass created by direct freezing of atmospheric gases (darker). This effects how quickly it sublimes in the local spring.  Scientists have gradually discovered that a large amount of water ice is just under the surface in polar regions.
@@ Line 255: / Line 256: @@
 The CO<sub>2</sub> transient caps are brightest in late spring and summer then in the early spring, with the exception of the [[Cryptic region]] near the South Pole, which remains relatively dark.  The reason for this is unclear.
 When the atmosphere is dusty, it is easier for snow (both CO<sub>2</sub> and water ice) to form. This results in the transient ice cap being brighter, and reflecting more light into space.
 Mars experiences large changes to its climate based on orbital dynamics (eccentricity, season of perihelion, and its obliquity) which have large effects on the isolation (amount of sunlight) in higher latitudes.  When the poles are pointed more directly at the sun during local summer, ALL of the permanent ice cap (both water and CO<sub>2</sub>) will vanish each Martian year.  This will put far more water and gas into play, bringing Mars into a 'warm wet' period for tens of thousands of years.
 For more detail, see [[Periodic climate changes on Mars]].
-As the polar winter ends in spring, the furthest edges receive direct sunlight and sublime.  However, the areas poleward remain very cold, and much of the newly freed CO<sub>2</sub> gas will freeze out further poleward.  Thus the pole's ice caps continue to get thicker in the early parts of spring.
+===Polar Clouds & Haze===
 Carbon dioxide can spontaneously nucleate ice particles in the atmosphere, forming hazes or clouds of CO<sub>2</sub>.  (Water ice almost never spontaneously nucleates on Mars, it virtually always condenses around dust particles.)  High clouds are visually always CO<sub>2</sub>, where as lower clouds could be CO<sub>2</sub> or water ice.
 When carbon dioxide freezes, it releases its latent heat of condensation, which warms the air around it.  This causes chaotic air flows around the freezing ice cap, mixing the air, and causing updrafts.  Compare this to the general slow flowing of atmosphere to the pole and the low pressure zone created by the atmosphere condensing out.  This makes modelling the atmosphere and clouds in the polar night challenging.  Observing this process going on is difficult as it takes place in unrelieved darkness, and is shrouded by clouds (both CO<sub>2</sub> and water).  We would like an orbiter with LIDAR scanners tuned to several IR frequencies to study this phenomena.
-There is evidence that buried below the southern permanent ice cap is large reserves of solid CO<sub>2</sub>.  The amount of this ice is somewhat speculative, but it is thought that if it were all to sublime, it would increase the pressure of the air to 180% of what it currently holds.  There are also likely CO<sub>2</sub> clathrates, tho they would only add a small amount of pressure (perhaps 0 to 1%).
+===Buried Carbon Dioxide Reserves at South Pole===
 There is evidence that buried below the southern permanent ice cap is large reserves of solid CO<sub>2</sub>.  The amount of this ice is speculative, but it is thought that if it were all to sublime, it would increase the pressure of the air to 180% of what it currently holds.  There are also likely CO<sub>2</sub> clathrates, tho they would only add a small amount of pressure (perhaps 0 to 1%).
-An unusual land form are the Martian [[Black spiders]] or 'araneiforms'.  These are formed by the movement of dust under a slab of solid carbon dioxide, breaking free thru cracks in the ice.
+===Fans and Spiders===
 ==Bibliography==

← Older revision		Revision as of 01:26, 26 November 2024
Line 270:		Line 270:

	The density of the seasonal ice caps is very hard to measure, but it is estimated that it is about 1,000 kg / m^2 when first deposited. It would likely increase in density from compression (of material falling on top) and by sintering.		The density of the seasonal ice caps is very hard to measure, but it is estimated that it is about 1,000 kg / m^2 when first deposited. It would likely increase in density from compression (of material falling on top) and by sintering.
		+
		+	An unusual land form are the Martian [[Black spiders]] or 'araneiforms'. These are formed by the movement of dust under a slab of solid carbon dioxide, breaking free thru cracks in the ice.

	==Bibliography==		==Bibliography==