| Title: |
Multidisciplinary Analyses of Terrestrial Samples Used to Interpret an Inorganic Origin (Anhydrite:Ce3+) for the 304 and 325‐nm Doublet Fluorescence Detected by the Mars 2020 SHERLOC Instrument at Jezero Crater. |
| Authors: |
Haney, N. C.1 (AUTHOR) nikole.c.haney@nasa.gov; Morris, R. V.2 (AUTHOR); Jakubek, R. S.3 (AUTHOR); Clark, J. V.1 (AUTHOR); Simon, J. I.2 (AUTHOR); Buckley, W. P.3 (AUTHOR); Downs, R. T.4 (AUTHOR); Rampe, E. B.2 (AUTHOR); Armytage, R. M. G.3 (AUTHOR); Graff, T. G.3 (AUTHOR); Burton, A. S.2 (AUTHOR); McCubbin, F. M.2 (AUTHOR); Berger, E. L.2 (AUTHOR); Tu, V. M.1 (AUTHOR); Casbeer, P. D.3 (AUTHOR); Mertzman, S. A.5 (AUTHOR); Williford, K. H.6 (AUTHOR); Scheller, E. L.7 (AUTHOR); Fornaro, T.8 (AUTHOR); Siljeström, S.9 (AUTHOR) |
| Source: |
Journal of Geophysical Research. Planets. Mar2026, Vol. 131 Issue 3, p1-30. 30p. |
| Subject Terms: |
Anhydrite; Calcium sulfate; Hydrothermal deposits; Impact craters; Thermolysis |
| 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 CaSO4 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:Ce3+ (trace‐Ce3+ for Ca2+ substitution in natural anhydrous CaSO4). Thermal decomposition products of natural volcanogenic gypsum (CaSO4·2H2O) and sedimentary glauberite (Na2Ca(SO4)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:Ce3+ thermal decomposition products. The 304 and 325‐nm doublet fluorescence detected by SHERLOC is fully explainable by inorganic anhydrite:Ce3+ 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:Ce3+ 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). Plain Language Summary: Certain sulfate‐bearing terrestrial samples associated with hydrothermal volcanism emit ultraviolet (UV) light when exposed to more energetic UV light. The emitted light (called fluorescence) was sourced from the mineral anhydrite (anhydrous Ca‐sulfate) with trace‐level replacement of Ca by trivalent cerium (anhydrite:Ce3+) using a multidisciplinary approach that included Raman and fluorescence spectroscopy, X‐ray diffraction, and elemental and thermal analyses. The same UV fluorescence was detected for anhydrite:Ce3+ produced in laboratory experiments by aerial thermal decomposition of natural hydrous Ca‐sulfate and anhydrous sodium‐calcium samples at temperatures above ∼450°C and ∼600°C, respectively. Anhydrite:Ce3+ fluorescence detected as an intrinsic property of unheated natural terrestrial samples and after aerial heating to ∼800°C document that the 304 and 325‐nm fluorescence doublet detected on Mars is fully explainable by anhydrite:Ce3+ and interpreted as inorganic in origin and not associated with organic molecules. As process analogs, the volcanogenic samples suggest Martian hydrothermal environments involving leaching and precipitation of CaSO4:Ce3+ in contact with the residue of leaching or, after aqueous transport, precipitation as vein precipitates, fracture fills, and evaporite deposits. Hydrothermal environments could also be associated with meteoritic impact melts and any other thermal source (e.g., contact and burial metamorphism). Key Points: The 304 and 325‐nm fluorescence at Jezero crater is fully explainable by trace Ce3+ for Ca2+ substitution in anhydrite (anhydrous CaSO4)Terrestrial volcanogenic samples have intrinsic inorganic 304 and 325‐nm doublet fluorescence sourced to anhydrite:Ce3+Formation pathways include hydrothermal precipitation (veins, fracture fills and evaporite deposits) and gypsum thermal decomposition [ABSTRACT FROM AUTHOR] |
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| Database: |
GreenFILE |