Reports

The majority of outflow channels on Mars are attributed to megafloods caused by the catastrophic release of groundwater. The most prominent outflow channels – located around the Chryse basin- are> 1000 km long and are estimated to be Hesperian (~3.7 – 3.1 Ga) in age (1–3). Marte Vallis in Elysium Planitia is the largest of the young (late Amazo-nian: ~0.5 Ga to present) outflow channels on Mars. The channel system extends over ~1000 km in length and ~100 km in width, making Marte Vallis comparable in scale to the Chryse basin channel systems. Young lava flows have fully embayed the most elevated portions of Marte Vallis, and as a consequence the fundamental characteristics of the channels, including their source, depth and morphology are less well understood than the Hesperian channels (4), despite being over 2.6 bil-lion years younger (5). Two possible sources have been proposed for Marte Vallis: Water flowing from the Athabasca Valles outflow channel in the west (4, 6, 7)