Laboratory Emissivity Spectra of Sulphide-Bearing Samples, New Constraints for the Surface of Mercury: Oldhamite in Mafic Aggregates

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first_page settings Order Article Reprints Open AccessArticle Laboratory Emissivity Spectra of Sulphide-Bearing Samples, New Constraints for the Surface of Mercury: Oldhamite in Mafic Aggregates by Cristian Carli 1,* [ORCID] , Sabrina Ferrari 2, Alessandro Maturilli 3, Giovanna Serventi 4, Maria Sgavetti 4, Arianna Secchiari 4,5, Alessandra Montanini 4 [ORCID] and Jörn Helbert 3 [ORCID] 1 National Institute for Astrophysics (INAF), Institute for Space Astrophysics and Planetology, Via Fosso del Cavaliere 100, 00133 Roma, Italy 2 Department of Geoscience, University of Padova, Via Gradenigo 6, 35131 Padova, Italy 3 German Aerospace Center (DLR), Institute for Planetary Research, Rutherfordstraße 23, 12489 Berlin, Germany 4 Department of Chemistry, Life Science and Environmental Sustainability, University of Parma, Parco Area delle Scienze, 11/a, 43124 Parma, Italy 5 Department of Earth Science “A. Desio”, University of Milan, Via Botticelli 23, 20131 Milano, Italy * Author to whom correspondence should be addressed. Minerals 2024, 14(1), 62; https://doi.org/10.3390/min14010062 Submission received: 25 September 2023 / Revised: 18 December 2023 / Accepted: 28 December 2023 / Published: 4 January 2024 (This article belongs to the Special Issue VNIR-TIR Spectroscopy: How Reflectance and Emissivity of Minerals, Rocks and Meteorites Can Help Planetary Exploration) Download keyboard_arrow_down Browse Figures Versions Notes Abstract Exploration of Mercury will continue in the near future with ESA/JAXA’s BepiColombo mission, which will increase the number and the type of datasets, and it will take advantage of the results from NASA’s MESSENGER (MErcury Surface, Space ENviroment, GEochemistry and Ranging) mission. One of the main discoveries from MESSENGER was the finding of a relatively high abundance of volatiles, and in particular of sulphur, on the surface. This discovery correlates well with the morphological evidence of pyroclastic activity and with features attributable to degassing processes like the hollows. BepiColombo will return compositional results from different spectral ranges and instruments, and, in particular, among them the first results from the orbit of emissivity in the thermal infrared. Here, we investigate the results from the emissivity spectra of different samples between a binary mixture of a volcanic regolith-like for Mercury and oldhamite (CaS). The acquisitions are taken at different temperatures in order to highlight potential shifts due to both mineral variation and temperature dependence on these materials that potentially could be present in hollows. Different absorption features are present for the two endmembers, making it possible to distinguish the oldhamite with respect to the regolith bulk analogue. We show how, in the mixtures, the Christiansen feature is strongly driven by the oldhamite, whereas the Reststrahlen minima are mainly dominated by mafic composition. The spectral contrast is strongly reduced in the mixtures with respect to the endmembers. The variations of spectral features are strong enough to be measured via MERTIS, and the spectral variations are stronger in relation to the mineralogy with respect to temperature dependence.