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Mars atmosphere

Atmospheric Composition and Life

Mars has less surface gravity than Earth. The force is just powerful enough to retain most gases, but it cannot prevent water vapour from evaporating into space. As a result, the water vapour concentration in the atmosphere of Mars is 30 times less than in the atmosphere of Earth. This explains the thin nature of the atmosphere of the red planet. The following diagram represents the composition of Mars’ atmosphere.

Carbon dioxide (CO2) 95.32 %
Nitrogen (N2) 2.7 %
Argon (Ar) 1.6 %
Oxygen (O2) 0.13 %
Water (H2O) 0.03 %
Carbon monoxide 0.07 %


No ozone layer on Mars

The quantities of ozone and water vapour are so small that, unlike the ozone layer on Earth, there is no protective layer on Mars that blocks out ultraviolet rays. The ultraviolet radiation reaches the soil unhindered and can destroy any organic molecules. For some, this fact is enough to argue that life is impossible on Mars.

Others, however, point out that there are ecological niches beneath the surface that may once have favoured the development of bacteriological colonies. These colonies may still persist to this very day. This possibility is a hot topic for discussion that will last for some time without other, more solid, evidence.


Water on Mars?

The surface of Mars is covered in enigmatic features that resemble those caused by running water on Earth. It is very likely that liquid water ran across the surface of mars in the past and even that Mars had an ocean. But how and why did this water disappear?



The Mars Odyssey spacecraft, which arrived at Mars on 24 October 2001, discovered a layer of water-ice in the planet’s soil. The ice consists of frozen mud in a layer of permafrost, about one metre beneath the surface. The Viking landers also photographed a faint shimmer on the planet’s soil at sunrise: a white layer of ice crystals (frost).

Mars-Express made the headlines in 2004 when the SPICAM and OMEGA instrument detected water ice in contact with the atmosphere on the Southern polar cap. Later, in 2005, the MARSIS radar instrument found not only that the lower layers of the polar caps were composed of almost pure water, it discovered some deep subterranean ice deposits at other latitudes. The mapping of these deposits is still on-going.

The amount of water present in the atmosphere of Mars never exceeds 100 micrometers. By way of comparison, Earth’s atmosphere is considered very dry when the amount of rain water does not exceed 1 mm. Further research is required to understand the water cycle on Mars.


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