The Gediz Vallis Inverted Channel: Evidence for Latestage Flow in Gale Crater, Mars?

The Mars Science Laboratory (MSL) Curiosity rover continues to ascend the foothills of Aeolis Mons (Mt. Sharp), Gale crater, Mars, with the goal of characterizing former habitable environments [1]. Previously, Curiosity encountered evidence for fluvial and lacustrine environments [2], which existed prior to the formation and exhumation of Aeolis Mons. An ongoing goal for the mission is to assess whether and how water and habitability persisted after the formation of Aeolis Mons. As of Sol 3702, Curiosity is approaching the mouth of Gediz Vallis, a ~9km long, ~500800 m wide, ~100250 m deep canyon incising into Aeolis Mons, possibly formed by wind and waterdriven erosion [3, 4]. On the Gediz Vallis floor are a series of landforms: a channel, an inverted channellike ridge, and Gediz Vallis ridge (GVR) [3]. The Gediz Vallis inverted channel (GVIC) is the first such landform to be encountered on the ground on Mars; elsewhere on Mars, inverted channels from orbit have been interpreted as filled fluvial valleys, ephemeral and perennial channels, and channelbelts [5]. Key questions for the GVIC include: Were the rocks which make up the GVIC deposited by flowing water, such as by a debris flow or streamflow? Did deposition occur across the wider GV floor, or was it restricted to the GVIC area? Does the GVIC comprise rocks deposited by one or multiple flow events? Here, we present both contextual orbital observations of the GVIC and longdistance observations as seen by Curiosity, and make initial interpretations of the depositional environment.