Astronauts on Mars. Artwork of astronauts on Mars with a US flag. 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.