Mars Atmospheric Features

The atmosphere of Mars is very thin. The atmospheric pressure on Mars is only about 7 to 9 hPa, while Earth's atmospheric pressure is about 1033 hPa. Mars' atmospheric pressure varies considerably with altitude. It is almost 9 hPa in the deepest depressions, but only 1 hPa at the top of Mount Olympus.

Mars' atmosphere is made mostly of carbon dioxide (95.3%). It also contains 2.7% nitrogen, 1.6% argon and traces of molecular oxygen (0.15%) carbon monoxide (0.07%) and water vapor (0.03%).

Mars experiences a slight greenhouse effect, much weaker than that of Earth.

The ozone layer, 40 km in height, is 1000 times smaller in concentration than the ozone layer of Earth. Therefore, it is incapable of blocking ultraviolet radiation.

Mars' atmosphere is dense enough to sustain very strong winds. These can cause large dust storms to cover the entire planet for months. These dust storms caused sand dunes to form in the Martian deserts.

The Martian sky has a soft salmon-pink color which comes from the scattering of light by dust grains of very fine iron from the soil.

Martian clouds come in three colors: pink, white and blue. Pink clouds are composed of dust particles about one micron in size. White clouds are believed to be made of water vapor, and blue clouds are thought to be made of ice crystals. At extreme latitudes, the condensation of carbon dioxide creates clouds made up of dry ice crystals.

Mars has no radiation belt, but it has an ionosphere, consisting of free electrons, 110 to 130 km above the planet's surface

Methane Gas

Observations made by the Mars Express spacecraft and the Keck telescope on Earth show that Mars' atmosphere contains methane gas in a ratio of 10 parts per billion.
This gas can only have a volcanic or biological origin. Since methane cannot remain long in the atmosphere, something - of either volcanic or biological origin - must be producing it.