Mercury

Mercury is the smallest (not including pluto, which is a dwarf planet) and innermost of the planets in our solar system. It's year, or orbit, around the sun is about 88 Earth days. Mercury is terrestrial, meaning that it is a "rocky" planet similar to Earth, Venus, and Mars.

Did you know?: Mercury is actually the second densest planet in the solar system. Just because Jupiter is big doesn't mean it's dense. Earth, surprisingly, is the most dense, but this is only attributed to its gravitational compression (gravity crushing down a planet into being smaller and therefore denser).

Mercury in color