Mars is the obvious frontrunner, but it is far from an easy second home. The other candidates reveal just how rare truly human-friendly conditions may be.

Earth’s tiny, temporary moons could become easy targets for sample-return missions. And we'll likely find more of them soon, thanks to the Rubin telescope.

Molten rock deep inside Earth can take up an extra supply of oxygen under pressure, according to a new study. That finding ...

Discover 15 facts about strange planet Earth, from underwater waterfalls and glowing seas to moving rocks and unusual ...