Answer: Earth

If you’re looking for the densest planet in our solar system, you don’t have to look far. Give your foot a swift stomp on the ground and rest easy knowing you’re living on the sturdiest rock for millions of miles around.

Thanks to a very dense inner and outer core (which collectively have an average density of around 12 grams per cubic centimeter) plus a fairly dense mantle, Earth has an average density of 5.51 grams per cubic centimeter. Our nearest neighbors on the density scale are Mercury, Venus, and Mars–the other three rocky terrestrial planets in our solar system.

If you’re looking for a place a bit more airy, you could always visit Saturn. The gas giant is the least dense planet in the solar system with an average density of a scant 0.70 grams per cubic centimeter.