Astronauts on Mars. Artwork of astronauts shaking hands on Mars, with a US flag in the background. The Martian atmosphere is mostly carbon dioxide and surface temperatures are well below freezing. Martian astronauts will have to breathe their own air supply and wear heated spacesuits. Mars is a rocky desert world with no surface water, and gravity is about one third of that on Earth. Human missions to explore Mars have been planned since the 1950s, usually involving a period of 10 to 30 years to develop the necessary technology and resources.