This drawing represents several features of the atmosphere on Mars including: dust storms, an atmospheric pressure much lower than found on Earth, and a composition primarily of carbon dioxide.
Click on image for full size
Lower Atmosphere
The atmosphere of Mars is much thinner than that of Earth, with a surface
pressure averaging 1/100th that at the surface of the Earth. Surface
temperatures range from -113oC at the winter pole to 0oC on the dayside
during summer.
Although the length of the Martian day (24 hours and 37
minutes) and the tilt of its axis (25 degrees) are similar to those on Earth (24 hours and 23.5 degrees), the
orbit of the planet about the Sun affects the lengths of the
seasons the most. The atmosphere is composed mainly of carbon dioxide (95.3%),
nitrogen (2.7%), and argon (1.6%), with small amounts of other gases.
Oxygen, which is so important to us on earth, makes up only 0.13% of the
atmosphere at Mars. There is only one-fourth as much water vapor in the
atmosphere.
Although small, this is thought to be enough to allow water
ice to be frozen into the surface of the planet. With so little water, clouds are rarely seen in the Martian sky. The
possible role in the past of liquid water in forming the dry river
beds which we can see is still unknown, particularly because water ice is
not plentiful on the surface of the planet.
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