Recent rivers on Mars...

if you define "recent" as one billion years according to this news release. Pull quote:

Using high-resolution images from the Mars Reconnaissance Orbiter, a spacecraft that orbits the planet, Dickson's group zoomed in on the eastern half of the crater and discovered about 20 winding valleys and a number of deposited materials typically found at the end of rivers. Counting the number of impact craters on the surface (the older the surface, the more impact craters it will have), the researchers managed to date the surface to about 1 billion years old.