In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars

TLDR

The rocks at Eagle crater are interpreted as a mixture of chemical and siliciclastic sediments with a complex diagenetic history. Sedimentary rocks at Eagle crater contain fine‑grained siliciclastic material, sulfates, and hematite, with cross‑stratification and diagenetic features indicating eolian and aqueous transport, episodic shallow water inundation, evaporation, desiccation, and a history that may have supported biological activity.

Abstract

Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features include hematite-rich concretions and crystal-mold vugs. We interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history. The environmental conditions that they record include episodic inundation by shallow surface water, evaporation, and desiccation. The geologic record at Meridiani Planum suggests that conditions were suitable for biological activity for a period of time in martian history.