Evidence for late alluvial activity in Gale crater, Mars

Abstract

The occurrence of past habitable conditions in Gale crater is generally associated with lacustrine and alluvial environments present >3 Ga ago, during the Hesperian Period on Mars. However, later-occurring aqueous activity is consistent with superposition relations between some alluvial deposits and bounding materials on the crater walls, preservation of fine-scale morphology on these alluvial deposits, and their superposing crater densities. The alluvial deposits include some not previously considered, and collectively lend confidence to the interpretation that local aqueous activity persisted in Gale crater into the Amazonian, or <2 Ga ago. Our conclusions are generally in accordance with late aqueous activity inferred from geochronology data (Martin et al., 2017), in addition to late alluvial activity elsewhere. Interpreted late aqueous activity points to possible habitable settings in Gale later than previously recognized.