Mars: Just The Facts . ... Credit Copyright: USGS , The Viking Project , NASA Explanation: Mars , the freeze-dried planet , orbits 137 million miles from the Sun or at about 1.5 times the Earth-Sun distance . It has two diminutive moons , towering extinct volcanos , an immense canyon system , a thin atmosphere chiefly composed of carbon dioxide (CO2), a frigid average surface temperature of -63 degrees Celsius , and permanent frozen CO2 polar caps which contain some water ice. ...