Jupiter’s Moon IO: Jupiter’s fifth moon, Io, is the most volcanically active body in the solar system. Io’s surface temperature averages about minus 202 degrees Fahrenheit (minus 130 Celsius), resulting in the formation of sulfur dioxide snowfields. But Io’s volcanoes can reach 3,000 F (1,649 C). Io is often referred to as a celestial body of fire and ice. (source)