What a great photo of the atmosphere of Mars. This was taken by the Viking I orbiter. Mars' atmosphere is composed of 95% carbon dioxide, molecular nitrogen (2.85%), and argon (2%). There is trace amounts of water vapor, oxygen, carbon monoxide, hydrogen, and noble gases. It is a much thinner atmosphere that Earth's, and much colder. The temperature is generally below zero to -60 degrees Celsius. The Martian atmosphere doesn't prevent Sun's radiation from getting to the surface. The thin atmosphere also cannot retain heat at the surface. It also prevents the existence of liquid water on the surface. Studies suggest that the Martian atmosphere was much thicker in the past. Science fiction has written about terraforming Mars in order to make it into a planet able to sustain life, mainly human life. In the real world, it is consider infeasible using present day technology. There is also ethical reasons for not terraforming Mars and the considerable cost an undertaking wou...