Wet Environments on Ancient Mars.

A colour-enhanced image of the delta in Jezero Crater, which once held a lake. Ancient rivers ferried clay-like minerals (shown in green) into the lake, forming the delta. Clays tend to trap and preserve organic matter, making the delta a good place to look for signs of ancient life.
Credit text: NASA

Image credit: NASA/JPL/JHUAPL/MSSS/Brown University.