Characterizing Hydrated Sulfates and Altered Phases in Jezero Crater Fan and Floor Geologic Units With SHERLOC on Mars 2020

The Mars 2020 Perseverance rover has explored fluvio-lacustrine sedimentary rocks within Jezero crater. Prior work showed that igneous crater floor Séítah and Máaz formations have mafic mineralogy with alteration phases that indicate multiple episodes of aqueous alteration. In this work, we extend the analyses of hydration to targets in the Jezero western fan delta, using data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectrometer. Spectral features, for example, sulfate and hydration peak positions and shapes, vary within, and across the crater floor and western fan. The proportion of targets with hydration associated with sulfates was approximately equal in the crater floor and the western fan. All hydrated targets in the crater floor and upper fan showed bimodal hydration peaks at ∼3,200 and ∼3,400 cm−1. The sulfate symmetric stretch at ∼1,000 cm−1 coupled with a hydration peak at ∼3,400 cm−1 indicate that MgSO4·nH2O (2 < n ≤ 5) is a likely hydration carrier phase in all units, perhaps paired with low-hydration (n ≤ 1) amorphous Mg-sulfates, indicated by the ∼3,200 cm−1 peak. Low-hydration MgSO4·nH2O (n = 1–2) are more prevalent in the fan, and hydrated targets in the fan front only had one peak at ∼3,400 cm−1. While anhydrite co-occurs with hydrated Mg-sulfates in the crater floor and fan front, hydrated Ca-sulfates are observed instead at the top of the upper fan. Collectively, the data imply aqueous deposition of sediments with formation of salts from high ionic strength fluids and subsequent aridity to preserve the observed hydration states.
We thank the SHERLOC and Mars 2020 science and engineering teams for the data that enabled this study. This research was supported by funds to the SHERLOC instrument team and the NASA Mars 2020 mission. Y.P. and B.L.E. were supported by a Mars-2020 SHERLOC Co-Investigator grant to B.L.E. S.Si. acknowledges funding from the Swedish National Space Agency (contract 2021-00092 and 137/19). A.D.C. was supported by the Mars 2020 Returned Sample Science Participating Scientist Program (NASA award number 80NSSC20K0237). Support for R.C.W. and S.C. was provided by a SHERLOC Co-Investigator grant to R.C.W. and by NASA contract NNH13ZDA018O. Funding for R.S.J. was provided as an Advanced Curation project run by the NASA Astromaterials Acquisition and Curation Office, Johnson Space Center under the Jacobs, JETSII contract. MPZ was supported by Grant PID2022-140180OB-C21 funded by MCIN/AEI/10.13039/501100011033/FEDER, UE. Research efforts carried out at the Jet Propulsion Laboratory, California Institute of Technology by K.H., S.Sh., K.U. were funded under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L.M. was supported by a Texaco Postdoctoral prize fellowship awarded by the division of Geological and Planetary Sciences of Caltech.