Images from Mars Express, Mars Global Surveyor, and the Mars Reconnaissance Orbiter have revealed ancient river valleys and deltas. The deltas show many thin layers just as deltas on Earth. Scientists speculate that features in Xanthe Terra show evidence of precipitation on early Mars.[2]
MOLA map showing boundaries of Xanthe Terra and other regions
Map of Xanthe Terra with major features labeled
Alluvial Fans in Mojave Crater, as seen by HiRISE. High ground is on the right. Branched network of channels runs from higher ground (crater rim) to lower ground.
References
^"Xanthe Terra". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.