The Atmosphere and Climate on Mars
|
Atmospheric Composition and Temperature Mars' atmosphere is very thin, about 100 times less dense tham Earth's. We don't see any clouds of water vapor, only a bit of water-ice clouds. Clouds that are found on the planet surface are made mainly from carbon dioxide-ice clouds and dust. Both the Temperature and the Pressure on the surface of Mars is very low. The pressure is equivalent to being in a high-altitude jet at 100,000 feet, and you would need a pressure suit to survive. The surface temperature ranges from around freezing (32 F) during the day, to more than -100 F at night, (depending on the season and hemisphere!). |
Carbon Dioxide (CO2), is the main constituent of the Martian atmosphere (95.3%) and 2.7% Nitrogen. At the very low pressures on Mars' surface, The CO2 only exists as a gas or solid (this is true on Earth, too. It's called DRY ICE! more on that soon).
Why is the pressure so low?
There is plenty of evidence that the pressure wasn't always so low.
Early volcanism would have released plenty of water and CO2 to
thicken the atmosphere. However, Mars being further from the sun,
the water might have too easily froze, and with the reduced
'greenhouse' warming of the atmospheric water, the temperature
would plumit further. Now even the CO2 condenses out of the
atmosphere at times.
The fact that the atmospheric surface pressure on Mars today is remarkably close to the "triple point" of water (below which liquid water is unstable) suggests that the atmosphere may be self-limiting.
If the atmosphere were to become thick enough for sufficient greenhouse warming to facilitate liquid water periodically at the surface, the CO2 would get removed as carbonates and tend to draw the atmosphere gradually back down to 6.1 millibars. This may be the reason for the particular value of the atmospheric pressure (and hence density) on Mars that we observe today.