Atmosphere of Mars
From The Book of THoTH (Leaves of Wisdom)
Mars, the fourth planet from the Sun, has a very different atmosphere from that of Earth. Lately, there has been a lot of interest in studying its composition, since the detection of a small amount of methane, which may signal life on Mars.
Mars' atmosphere is very thin: the atmospheric pressure on the surface is only 0.7-0.9 kPa, compared to Earth's 101.3 kPa. However, the scale height of the atmosphere is about 11 km, somewhat higher than Earth's 6 km. The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water. The atmosphere is quite dusty, giving the Martian sky a tawny color when seen from the surface; data from the Mars Exploration Rovers indicates the suspended dust particles are roughly 1.5 micrometres across Lemmon et al., "Atmospheric Imaging Results from the Mars Exploration Rovers: Spirit and Opportunity".
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Methane
In March 2004 the Mars Express Orbiter confirmed the presence of methane in the Martian atmosphere, with a concentration of about 10 ppb by volume "Mars Express confirms methane in the Martian atmosphere" - March 30, 2004 ESA Press release. URL accessed March 17, 2006. The presence of methane on Mars would be very intriguing, since as an unstable gas it indicates that there must be (or have been within the last few hundred years) a source of the gas on the planet. Volcanic activity, comet impacts, and the existence of life in the form of microorganisms such as methanogens are among possible but as yet unproven sources. The methane appears to occur in patches, which suggests that it is being rapidly broken down before it has time to become uniformly distributed in the atmosphere, and so it is presumably also continually being released to the atmosphere. Plans are now being made to look for other companion gases that may suggest which sources are most likely; in the Earth's oceans biological methane production tends to be accompanied by ethane, while volcanic methane is accompanied by sulfur dioxide.
It was also recently shown that methane could be produced by a non-biological process involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars. "Have olivine, will gas: Serpentinization and the abiogenic production of methane on Mars". The required conditions for this reaction (i.e. temperature and pressure) don't exist on the surface, but likely exist within the crust. To prove this is process is occurring, one could try detecting serpentine, a mineral by-product of the process.
Temperature
The thin atmosphere cannot hold heat and is the cause of the lower temperatures on Mars. The maximum temperature is roughly 20 degrees Celsius (68 degrees Fahrenheit). Recently, evidence has been discovered suggesting that Mars may be warming in the short term. Orbiter's Long Life Helps Scientists Track Changes on Mars
Water
Other aspects of the Martian atmosphere vary significantly. In the winter months when the poles are in continual darkness, the surface gets so cold that as much as 25% of the entire atmosphere condenses out into thick slabs of CO2 ice (dry ice). When the poles are again exposed to sunlight the CO2 ice sublimates, creating enormous winds that sweep off the poles as fast as 250 mph (400 km/h). These seasonal actions transport large amounts of dust and water vapor giving rise to Earth-like frost and large cirrus clouds. These clouds of water-ice were photographed by the Opportunity rover in 2004. "Mars Rovers Spot Water-Clue Mineral, Frost, Clouds"
See also
--Angel 16:41, 26 May 2006 (CDT)
Categories: Mars | Planetary atmospheres
