The presence of talc following carbonated serpentization has been linked to Earth analogs in terrestrial greenstone belts such as the Pilbara in Western Australia, where talc bearing komatiite cumulate units of the Dresser Formation overlie the siliceous, stromatolite-bearing Strelley Pool Chert unit (Van Kranendonk and Pirajno, 2004). If a similar relationships exists on Mars, investigations of rocks stratigraphically beneath the talc-bearing units at Nili Fossae may provide the best chance to examine well preserved, siliceous organics. This hypothesis is testable at the Southern Nili Fossae proposed landing site, for example.
In preparation for the the Mars 2020 landing site, we are examining the thermodynamic relationships that favor formation of serpentine and talc-carbonate and different pressures and temperatures in the crust (Barnes 2007). This is important as it will constrain the low grade metamorphism required to replicate the proposed models of serpentinisation and help us understand the regional metamophic gradient that is critical to furthering our knowledge of the ancient rocks of Nili Fossae.