Atmosphere of Mars

Further information: Climate of Mars
Atmosphere of Mars
Mars
Image of Mars and its thin atmosphere, photographed by Emirates Mars Mission
General information[2]
Average surface pressure610 Pa (0.088 psi; 4.6 mmHg; 0.0060 atm)
Mass2.5x1016 kg[1]
Composition[3][4]
Carbon dioxide95%
Nitrogen2.8%
Argon2%
Oxygen0.174%
Carbon monoxide0.0747%
Water vapor0.03% (variable)

The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.85%), and argon (2%).[3] It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and noble gases.[3][5][2] The atmosphere of Mars is much thinner and colder than Earth's having a max density 20g/m3 (about 2% of Earth’s value) with a temperature generally below zero down to -60 Celsius. The average surface pressure is about 610 pascals (0.088 psi) which is 0.6% of the Earth's value.[2]

The currently thin Martian atmosphere prohibits the existence of liquid water on the surface of Mars, but many studies suggest that the Martian atmosphere was much thicker in the past.[4] The higher density during spring and fall is reduced by 25% during the winter when carbon dioxide partly freezes at the pole caps.[6] The highest atmospheric density on Mars is equal to the density found 35 km (22 mi) above the Earth's surface and is ≈0.020 kg/m3.[7] The atmosphere of Mars has been losing mass to space since the planet's core slowed down, and the leakage of gases still continues today.[4][8][9]

The atmosphere of Mars is colder than Earth’s owing to the larger distance from the Sun, receiving less solar energy and has a lower effective temperature, which is about 210 K (−63 °C; −82 °F).[2] The average surface emission temperature of Mars is just 215 K (−58 °C; −73 °F), which is comparable to inland Antarctica.[2][4] Although Mars' atmosphere consists primarily of carbon dioxide, the greenhouse effect in the Martian atmosphere is much weaker than Earth's: 5 °C (9.0 °F) on Mars, versus 33 °C (59 °F) on Earth due to the much lower density of carbon dioxide, leading to less greenhouse warming.[2][4] The daily range of temperature in the lower atmosphere presents ample variation due to the low thermal inertia; it can range from −75 °C (−103 °F) to near 0 °C (32 °F) near the surface in some regions.[2][4][10] The temperature of the upper part of the Martian atmosphere is also significantly lower than Earth's because of the absence of stratospheric ozone and the radiative cooling effect of carbon dioxide at higher altitudes.[4]

Dust devils and dust storms are prevalent on Mars, which are sometimes observable by telescopes from Earth,[11] and in 2018 even with the naked eye as a change in colour and brightness of the planet.[12] Planet-encircling dust storms (global dust storms) occur on average every 5.5 Earth years (every 3 Martian years) on Mars[4][11] and can threaten the operation of Mars rovers.[13] However, the mechanism responsible for the development of large dust storms is still not well understood.[14][15] It has been suggested to be loosely related to gravitational influence of both moons, somewhat similar to the creation of tides on Earth.

The Martian atmosphere is an oxidized atmosphere. The photochemical reactions in the atmosphere tend to oxidize the organic species and turn them into carbon dioxide or carbon monoxide.[4] Although the most sensitive methane probe on the recently launched ExoMars Trace Gas Orbiter failed to find methane in the atmosphere over the whole of Mars,[16][17][18] several previous missions and ground-based telescopes detected unexpected levels of methane in the Martian atmosphere, which may even be a biosignature for life on Mars.[19][20][21] However, the interpretation of the measurements is still highly controversial and lacks a scientific consensus.[21][22]

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  12. ^ https://skyandtelescope.org/astronomy-news/is-the-mars-opposition-already-over/[Normally reddish-orange or even pink, Mars now glows pumpkin-orange. Even my eyes can see the difference. ALPO assistant coordinator Richard Schmude has also noted an increase in brightness of ≈0.2 magnitude concurrent with the color change.]
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  22. ^ Cite error: The named reference Zahnle-2011 was invoked but never defined (see the help page).