¹Javier Cuadros,²Joseph R.Michalski,³Janice L.Bishop,¹Christian Mavris,⁴Saverio Fiore,⁵Vesselin Dekov
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114704]
¹Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
²Department of Earth Sciences & Laboratory for Space Research, The University of Hong Kong, Hong Kong, China
³SETI Institute, Mountain View, CA 94043, USA
⁴Institute of Methodologies for Environmental Analysis, CNR, Department of Geoenvironmental and Earth Sciences, University of Bari, Via Orabona 4, 70125 Bari, Italy
⁵Department of Marine Resources and Energy, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
Copyright Elsevier

The cameras on the Pathfinder probe (Imager for Pathfinder) and the rovers Spirit and Opportunity (Panoramic Camera), Curiosity (Mast Camera) and Perseverance (Mast Camera-Z) produce visible-range spectra of limited wavelength resolution but of great target resolution which allows mineralogical analysis of selected areas within martian rocks. Laboratory spectra of relevant specimens were transformed into the spectra corresponding to each of the above cameras to increase our capability to interpret martian spectral data collected in-situ. The focus was on finding spectral features that can be detected by the cameras on Mars and are diagnostic of specific minerals. The samples are a collection of (1) Fe/Mg-phyllosilicates from submarine hydrothermal sites and (2) of rocks from acid alteration environments containing goethite, hematite, jarosite and Fe-bearing chlorite as these minerals are detectable in the extended visible range. Among all the samples, interstratified glauconite-nontronite has the most unique spectral features and should be easily detectable with the rover cameras. The spectral features of talc from Fe-bearing interstratified specimens are described. These data are especially relevant as glauconite and talc have been proposed to be fairly abundant on Mars and their detections are suggested from remote-sensing near-IR data. Several indices are proposed to assess Fe content on the investigated samples as well as mineral concentration of goethite and hematite. Among these indices, the normalized spectral slope in the range 420–600 nm increases with total Fe content for all samples, whether phyllosilicates, oxides or sulphates (R2 = 0.7–0.8). For pure phyllosilicates, the slope from 600 to 1010 nm decreases with increasing octahedral Fe (R2 = 0.75). An index for goethite produced excellent results assessing goethite concentration (R2 = 0.84). Of all cameras, Mast Camera reproduces the spectra with lowest fidelity and generates the poorest correlations between indices and tested variables. The other three cameras perform similarly.

¹Andrea Wenzel,²Justin Filiberto,³Natasha Stephen,⁴Susanne P. Schwenzer,⁵Samantha J. Hammond
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13737]
¹Department of Geology, Southern Illinois University, Carbondale, Illinois, 62901 USA
²Lunar and Planetary Institute, USRA, Houston, Texas, 77058 USA
³Plymouth Electron Microscopy Centre, University of Plymouth, Drake Circus, Plymouth, PL4 8AA UK
⁴AstrobiologyOU, School of Environment, Earth, and Ecosystems Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
⁵School of Environment, Earth, and Ecosystems Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
Published by arrangement with John Wiley & Sons

Northwest Africa 6963 (NWA 6963) is a coarse-grained, gabbroic Martian meteorite that further extends our Martian sample collection, both compositionally and texturally. Gabbroic shergottite NWA 6963 provides direct petrologic evidence of intrusive igneous conditions within the Martian crust. Here, we analyzed geochemical zoning profiles and microstructural-crystallographic information from electron backscattered diffraction of augite and pigeonite to constrain the crystallization history of NWA 6963. Compositional zoning profiles reveal pyroxenes with augite or pigeonite cores mantled by Fe-rich pigeonite rims. Our results suggest complex pyroxene textures and zoning profiles observed in pyroxenes in NWA 6963 are due to pyroxene accumulation from a crystallizing magma in a large intrusive environment (sill or magma chamber); however, without geologic context or companion samples, it is currently impossible to rule out accumulation at the base of a very large (>>100 m) differentiated flow.