Astronauts on Mars. Computer artwork of astronauts exploring the surface of Mars. The Martian atmosphere is mostly carbon dioxide and surface temperatures are well below freezing as Mars is much further from the Sun than the Earth. Martian astronauts will have to breathe their own air supply and wear heated spacesuits on the surface of Mars. Mars is a rocky desert world and has no surface water. The red-orange colour of the Martian rocks is due to a high iron oxide content. In 2004, NASA announced the Constellation Program, a US space program intended to put astronauts back on the Moon by 2020, followed by missions to Mars.