In situ crystallographic mapping constrains sulfate precipitation and timing in Jezero crater, Mars.

Abstract

Late-stage Ca-sulfate-filled fractures are common on Mars. Notably, the Shenandoah formation in the western edge of Jezero crater preserves a variety of Ca-sulfate minerals in the fine-grained siliciclastic rocks explored by the Perseverance rover. However, the depositional environment and timing of the formation of these sulfates are unknown. To address this outstanding problem, we developed a technique to map the crystal orientations of these sulfates in situ at two stratigraphically similar locations in the Shenandoah formation, allowing us to constrain the burial depth and paleoenvironment at the time of their precipitation. Our crystal orientation mapping results and outcrop-scale fracture analyses reveal two different generations of Ca-sulfates: one likely precipitated in the shallow subsurface and a second one that formed at a burial depth below 80 meters. These results indicate that two studied locations capture two different times and distinct chemical conditions in the sedimentary history of the Shenandoah formation, providing multiple opportunities to evaluate surface and subsurface habitability.