Io
A small moon of Jupiter (small meaning it is just slightly larger than Earth’s Moon), Io has hundreds of volcanoes peppering its surface that spew lava dozens of miles into its sky; combined with its thin, sulfurous atmosphere, the moon is pretty hellish. Immense tidal forces from Jupiter cause the moon’s surface to shift by hundreds of feet to and fro. Since the moon is so superhot and unstable, all observations of Io have been done from a distance.
