The exoplanet HD 20794d swoops in and out of its habitable zone every few hundred days, making for an extreme climate.

But how well do you really know our planetary neighbor? This quiz of 15 questions will test your knowledge of Mars' size, surface and history, as well as scientists' attempts to study it. Remember to ...

HWO will be the first space telescope built to find potentially habitable planets and analyze their atmospheres for signs of ...

A U.S. scientist searching for a civilization across 7 Earth clones circling the red dwarf star TRAPPIST-1 says its own alien ...