A Moon With The Most Volcanic Activity Of Anything In The Solar System

This moon looks even more like it's made from green cheese than ours does, but it's not. Lame. Io, the innermost moon of Jupiter, is the most volcanically active body in our solar system because of gravitational "tides" exerted by Jupiter and its other moons. And the constantly flowing lava gives Io's surface frequent makeovers.

This image was created with data from NASA's Galileo spacecraft collected in 1996. I0's appearance has presumably changed a lot since then, but there are still cool things to notice in this image. For example, there aren't any craters visible on Io's surface (all those pits and holes are volcanoes) so the ash deposits and lava flowing across the surface must fill or cover craters more quickly than they are created. This image also depicts the side of Io that always faces away from Jupiter, providing a look at the dark side of the moon. Sort of. [Astronomy Picture of the Day]