Using data from the Context Camera aboard NASA’s Mars Reconnaissance Orbiter, planetary researchers have generated an 8-trillion-pixel global map of Mars and performed the first systematic global survey of Martian fluvial (river) ridges. This image shows a suite of fluvial ridges on Mars (at –67.64 °E, 43.37 °S). Image credit: J. Dickson. Mars used to be a wet world, as evidenced by rock records of lakes, rivers, and glaciers. The Martian river ridges were formed between 4 and 3 billion years ago (the Noachian to Hesperian period), when large rivers deposited sediments in their channels, rather than only having the water cut away at the surface.