Reconstructing the distribution and depositional history of the sedimentary deposits of Arabia Terra, Mars

The sedimentary deposits of Meridiani Planum formed during the martian climate transition at the Noachian–Hesperian boundary between warm–wet and cold–dry conditions, and give valuable insight into how and when this transition occurred. We show that these deposits share characteristics with sedimentary outcrops across Arabia Terra. Despite near-ubiquitous dust cover across much of Arabia Terra, spectral signatures of polyhydrated sulfate minerals resembling those in Meridiani were identified in Schiaparelli and another unnamed crater. An erosional morphology analysis using both image and topographic data was then used to identify morphologies characteristic of Meridiani-type deposits and catalogue their occurrences throughout Arabia Terra. The occurrences of deposits with compositions and morphologies resembling the Meridiani deposits throughout Arabia Terra suggest that Meridiani-type sedimentary rocks were once more widespread. Elevations of the eroded remnants were used to reconstruct the pre-erosional paleo-surface of the deposits. Within this study area, these deposits once covered ∼2.5–3.6 × 106 km2 and represent an eroded volume of 0.9–1.7 × 106 km3 of sediment. Crater retention ages using craters of a range of preservation states and stratigraphic levels reveal that the deposits were laid down and subsequently eroded during a ∼270 Myr period between ∼3.83 and 3.56 Ga. The deposits formed following the transition from fluvial dissection to evaporite deposition at the end of the Noachian. The high erosion rates (∼3 × 10−6 m/yr) suggest that Mars may have maintained a thick atmosphere relative to today even as it dried out in the Early Hesperian.