The Atmosphere
of Mars

Mars is quite similar to the Earth in its rotation rate and the tilt of its axis, so both the daily and seasonal changes of the Martian atmosphere are much like the Earth's. Both the Earth and Mars also have similar global atmospheric circulation patterns.
marsatmo
 The atmosphere of Mars, however, is quite different from that of Earth. The Martian atmosphere is composed primarily of carbon dioxide with small amounts of other gases. The air is thin and unbreathable and contains 95% carbon dioxide, 3% nitrogen, 1.5% argon, trace amounts of water, and no oxygen. (Earth has 78% nitrogen, 21% oxygen, 1% argon, and 0.03% carbon dioxide.)  Atmospheric surface pressure is estimated at between 6 and 7 millibars, or about 1/150th  that of the Earth.

Martian air contains only about 1/1,000th  as much water as our air! Yet, even this small amount of water can condense out and form clouds. Local patches of early morning fog can form in valleys. At the Viking Lander 2 site, a thin layer of water frost was seen covering the ground each winter morning.

Fog frostsmall

Scientists believe that in the past a denser Martian atmosphere may have allowed water to flow on the planet. Physical features closely resemble shorelines, riverbeds, and islands. This suggests that great rivers and possibly seas once existed on Mars.

Network.

 Islands

While the average temperature on Mars is about -67°F (-55°C), Martian surface temperatures range widely from as little as -207°F (-133°C) at the winter pole to almost 80°F (27°C) on the dayside during summer. Click here for the daily Martian weather report!

For answers to some of the most common questions about the weather, climate, and geology of Mars, click here.

Questions to think about:

  • What types of features might your Mars space suit need to have?
  • Do you think you could grow plants on the Martian surface? Why?

NEXT... The Geology of Mars: Volcanoes