The Atmosphere of Mars - Learn with audio





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Published on Jul 19, 2011

Mars lost its magnetosphere 4 billion years ago,[94] so the solar wind interacts directly with the Martian ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected these ionised atmospheric particles trailing off into space behind Mars.[94][95] Compared to Earth, the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface ranges from a low of 30 Pa (0.030 kPa) on Olympus Mons to over 1,155 Pa (1.155 kPa) in the Hellas Planitia, with a mean pressure at the surface level of 600 Pa (0.60 kPa).[96] The surface pressure of Mars is equal to the pressure found 35 km[97] above the Earth's surface. This is less than 1% of the Earth's surface pressure (101.3 kPa). The scale height of the atmosphere is about 10.8 km,[98] which is higher than Earth's (6 km) because the surface gravity of Mars is only about 38% of Earth's, an effect offset by both the lower temperature and 50% higher average molecular weight of the atmosphere of Mars.

The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon and contains traces of oxygen and water.[6] The atmosphere is quite dusty, containing particulates about 1.5 µm in diameter which give the Martian sky a tawny color when seen from the surface.[99]

Methane has been detected in the Martian atmosphere with a mole fraction of about 30 ppb;[12][100] it occurs in extended plumes, and the profiles imply that the methane was released from discrete regions. In northern midsummer, the principal plume contained 19,000 metric tons of methane, with an estimated source strength of 0.6 kilogram per second.[101][102] The profiles suggest that there may be two local source regions, the first centered near 30° N, 260° W and the second near 0°, 310° W.[101] It is estimated that Mars must produce 270 ton/year of methane.[101][103]

The implied methane destruction lifetime may be as long as about 4 Earth years and as short as about 0.6 Earth years.[101][104] This rapid turnover would indicate an active source of the gas on the planet. Volcanic activity, cometary impacts, and the presence of methanogenic microbial life forms are among possible sources. Methane could also be produced by a non-biological process called serpentinization[b] involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars

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