Ancient Mars. Computer artwork of Mars at least 3 billion years ago. The surface environment of ancient Mars was different to that of today, and may have allowed life forms to develop. Ancient Mars was warm, with seas and lakes covering much of its surface; it also had a thick atmosphere (blue). Today, water is present on Mars only as ice on the surface in the polar regions, underground or as trace amounts of vapour or ice crystals in the atmosphere. The atmospheric pressure of modern Mars is only 0.6% that of Earth's, and the average surface temperature is - 33 degrees Celsius. This means that it is extremely unlikely that life still exists on Mars.