Pluto’s Cave is a partially collapsed lava tube in the Klamath National Forest with a depth of some 1,200 feet. Here's everything to know about the Northern California cavern.

Pluto was always in a tough spot when it came to being a planet. Just 1,477 miles across, it's only one-fifth the diameter of Earth. It did have five known moons: Charon, Nix, ...

If being downgraded from planet to dwarf planet back in 2006 was one identity crisis for Pluto, here’s another: Scientists now say the ninth rock from the sun could be a sort of giant comet ...