Scientists have used orbiters and rovers to find dried streams, lakes, and gullies on Mars that hint at its watery past, but their cavalry of robots has struggled to prove the Red Planet ever had ...

Planetary geologists and astronomers studying Mars have known for decades that water was once likely present on the planet, after NASA's Mariner 9 mission captured images of dry gullies in the 1970s.

Roundheaded gullies slice into that same smooth layer, while strange tongues of who-knows-what lap at the slopes beneath them. Landscapes like this are changing the way geologists look at Mars.

A study using radar data from China's now-dead Zhurong rover finds strong evidence that Mars had a stable ocean in the ancient past.