Multidisciplinary Analyses of Terrestrial Samples Used to Interpret an Inorganic Origin (Anhydrite:Ce ³⁺ ) for the 304 and 325‐nm Doublet Fluorescence Detected by the Mars 2020 SHERLOC Instrument at Jezero Crater

Abstract Doublet fluorescence at 304 and 325‐nm under deep ultraviolet (DUV) excitation was detected on Mars at Jezero crater by the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard the Mars 2020 rover Perseverance . The doublet was associated with CaSO 4 phases and sourced to organic molecules as the preferred interpretation (Sharma et al., 2023, https://doi.org/10.1038/s41586‐023‐06143‐z ). Reported here are coordinated analyses of terrestrial volcanogenic samples that have, under DUV excitation, intrinsic 304 and 325‐nm fluorescence whose origin is tightly sourced to anhydrite:Ce 3+ (trace‐Ce 3+ for Ca 2+ substitution in natural anhydrous CaSO 4 ). Thermal decomposition products of natural volcanogenic gypsum (CaSO 4 ·2H 2 O) and sedimentary glauberite (Na 2 Ca(SO 4 ) 2 ) by aerial heating at more than 450°C and more than 600°C, respectively, are also characterized by 304 and 325‐nm fluorescence doublets that are sourced from anhydrite:Ce 3+ thermal decomposition products. The 304 and 325‐nm doublet fluorescence detected by SHERLOC is fully explainable by inorganic anhydrite:Ce 3+ resulting from geogenic processes. The volcanogenic samples are products of leaching and precipitation in hydrothermal environments. Leachates can precipitate in many ways, including intimate or proximal contact with residues and, after aqueous transport, as vein precipitate, fracture fill, and evaporite deposits. Equivalent considerations extend to hydrothermalism driven by impact melts and other thermal sources. Laboratory thermal decomposition of progenitor phases to anhydrite:Ce 3+ is an analogous process for contact and burial metamorphism. The coordinated analysis approach additionally includes major element and REE abundances (X‐ray fluorescence and inductive coupled plasma—mass spectrometry), X‐ray diffraction, DUV Raman spectroscopy, and thermal analysis (thermal gravimetry, differential scanning calorimetry, and evolved gas analysis).