Compare and contrast the evolution of the atmospheres of Mars, Venus, and Earth.
-- All three have secondary atmospheres created by volcanoes.
-- Venus, which is closest to the Sun, experienced temperatures which prevented the CO2 from settling out of the atmosphere and dissolve into the oceans. Venus became a victim of the runaway greenhouse effect and the H2O in the atmosphere was destroyed by UV sunlight.
-- Earth was far enough from the Sun that liquid water could form, eventually creating oceans, which dissolved much of the CO2 present in the atmosphere. The small amounts of H2O and CO2 in the Earth's atmosphere create an insulating layer that creates a greenhouse effect which is just enough to keep the Earth warm and liquid.
-- Mars once had liquid water and enough water to dissolve the CO2 in the atmosphere, but because it was less massive than Venus or Mars it lost its CO2. Once Mars lost its CO2, the atmosphere thinned to the point that most of the IR radiation escaped. Also, Mars's volcanism stopped very early in its formation which prevented the atmosphere from having its H2O and CO2 renewed.