Moons of the Solar System
3 of 10
Orbiting Jupiter is the moon Callisto. This moon is about the same size as the planet Mercury, but similarities between the two end there. Oxygen has been detected near the surface of Callisto, and like its neighboring moon, Europa, it may have liquid beneath its icy cratered surface.
Fun Fact: Callisto has had the most impact craters in the solar system, which have left many large cracks in its surface.
Photo source: NASA