how mars' atmosphere relates to its temperature
Climate of Mars Some scientists maintain that the great mass of the Tharsis volcanoes has had a major influence on Mars's climate. Erupting volcanoes give off great amounts of gas, mainly water vapor and CO2. Enough gas may have been released by volcanoes to have made the earlier Martian atmosphere thicker than Earth's. The volcanoes could also have emitted enough H2O to cover the whole Martian surface to a depth of 120 m (390 ft). CO2 is a greenhouse gas that raises the temperature of a planet: it traps heat by absorbing infrared radiation. So Tharsis volcanoes, by giving off CO2, could have made Mars more Earth-like in the past. Mars may have once had a much thicker and warmer atmosphere, and oceans and/or lakes may have been present.[10] It has, however, proven extremely difficult to construct convincing global climate models for Mars which produce temperatures above 0 °C at any point in its history,[11] although this may simply reflect problems in accurately calibrating such models.