Modeling Water-Rock Reactions Beneath the Greenheugh Pediment, Gale Crater, Mars

The Mars Science Laboratory Curiosity rover has been exploring the clay rich Glen Torridon unit in Gale crater since sol 2300 of the mission [1]. As identified in orbital data [2], this clay rich area [3] in the Murray formation is overlain with the Greenheugh Pediment unit to the south, which is part of the Stimson Formation [4]. Curiosity acquired the drill sample Hutton in the Upper Murray formation 2 – 3 meters below the Greenheugh Pediment [5,6]. This study uses thermochemical modelling to investigate the hypothesis for alteration in the Murray formation below the Greenheugh Pediment. Specifically, if the contact between the Greenheugh Pediment and Murray sediments was a conduit for diagenetic fluids (a low water/rock scenario) or if subaerial weathering altered the Murray sediments before cementation began (a high water/rock scenario) [6]. Here, we report on preliminary modeling where we have reacted the chemical composition for the Hutton drill sample with Gale Portage Water (GPW) at 25 °C, 50 °C and 200 °C, for 10% Fe3+/Fetot of the host rock.