GSA Connects 2021 in Portland, Oregon

Paper No. 14-1
Presentation Time: 8:00 AM


STACK MORGAN, Kathryn, Planetary Geosciences, Jet Propulsion Laboratory, Caltech, 4800 Oak Grove Drive, Pasadena, CA 91109, FARLEY, Kenneth A., Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, WILLIFORD, Kenneth H., Department of Earth, Planetary, and Space Sciences, University of California-Los Angeles, 595 Charles E Young Dr E, Los Angeles, CA 90095-1567 and SCIENCE TEAM, Mars 2020, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109

In February 2021, NASA’s Mars 2020 Perseverance rover landed successfully at Octavia E. Butler Landing in Jezero crater, the site of an ancient open-system lake on Mars. Perseverance is seeking signs of ancient life and is collecting martian rock and soil samples for possible return to Earth by a future mission. Upon completing a ~90 day commissioning phase, Perseverance embarked on an exploration and sampling campaign of the rocks and outcrops comprising the present-day floor of Jezero crater. This abstract summarizes mission results from Perseverance’s first eight months on Mars, including the lead-up to the collection of the missions’ first sample(s).

Rover observations reveal that the crater-retaining units of the Jezero crater floor are comprised of variably massive and layered mafic rocks exposed in flat polygons and high-standing, erosion-resistant outcrops. Crater floor rocks are heavily ventifacted and often exhibit a rough, granular surface texture. This, combined with an abundance of dust and a purplish mottling that may be a coating or rind, have made definitive lithological interpretation challenging. Crater floor rocks exposed west of the landing site in a region named Séítah (Navajo for “amongst the sand”) are distinguished from the surrounding crater floor units by a distinct topographic boundary, olivine signatures observed in orbiter and rover spectroscopic data, and well-developed bedding. Observations from Perseverance’s early exploration of the Jezero crater floor units are consistent with clastic, likely sedimentary, deposition in subaqueous settings, although alternate subaerial sedimentary and volcanic interpretations are still being explored. Long-distance imaging of the ancient delta preserved in the western part of the crater and of remnant deposits of formerly more extensive deltaic and possibly lacustrine deposition provide evidence for the progradation of a Gilbert-style delta into an ancient lake, followed by a period of high-energy flooding after lake level fall. When coupled with observations of the Jezero delta, Perseverance’s investigation of the crater floor supports a model involving the evolution of a long-lived fluvio-lacustrine system in which multiple episodes of deposition occurred between several geologically significant hiatuses.