Sedimentary strata in the southern highlands of Noachis Terra, Mars

The sedimentary history of Mars is one of the fundamental problems that needs to be understood in order to determine the role of the atmosphere, climate, and water in sculpting the martian surface. To begin addressing this issue, a number of sedimentary strata, some up to several hundreds of meters thick, have been studied in the southern highlands of Mars using THEMIS VIS and IR (both day and night) images. A sequence of sedimentary units was found in a pit eroded into the floor of Rabe Crater (35° E, 44° S), some of which appear to be shedding dark sand that feeds into the Rabe Crater dune field. The visible and thermal characteristics of these units are similar to other units found across Noachis Terra (which extends from 0°-60° E, 30°-65° S, and includes Rabe Crater), leading to the hypothesis that a series of region-wide depositional events occurred at some point in the martian past, and that these deposits are currently exposed by erosion in pits on crater floors and possibly on the intercrater plains separating the craters. Some of these sedimentary units may consitute a source of sand for the many intracrater dune fields in Noachis Terra, eroding from a widespread source that outcrops locally. Sand-bearing layers that extend across all or part of Noachis Terra are not likely to be dominated by loess or lacustrine deposits; glacial and/or volcanic origins are more plausible.