Royal Society Publishing

A New Look to the Martian Atmosphere

G. E. Hunt


Although the Martian atmosphere is at present only about 1% as dense as the Earth's atmosphere it has been revealed as a dramatically active environment by the observations made during 1971-72 by the Mariner 9 and Soviet Mars 2 and 3 spacecrafts which arrived at the planet during a major global dust storm. Local dust storms were seen to change in intensity on a daily basis and other evidence for winds were seen in cloud patterns and in visible streaks on the planet's surface. Cloud layers composed of both CO$_{2}$ and water ice have been observed. The variations in the albedos of surface markings are probably caused by the wind blow dust. At the present time the lower atmosphere is found to consist mainly of CO$_{2}$ with traces of CO, O$_{3}$, O$_{2}$, and H$_{2}$O. Geological evidence of channels and gullies suggests erosion by water at some stage of the planet's development although it is also possible that wind erosion has played a role in sculpturing these features. Periodic variations in the Martian climate may be created through variations in the planets obliquity and orbital eccentricity over time scales of 25 000 years. Mars today, then, may be in a temporary ice age.

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