¹Alessandro Pisello (>10)
Journal of Geophysical Research: Planets 131, e2025JE009371 Open Source Link to Article [DOI: 10.1029/2025JE009371]
¹Department of Physics and Geology, University of Perugia, Perugia, Italy
Published by arrangement with John Wiley & Sons

Understanding how the glass/crystal ratio influences the spectral response of volcanic rocks is crucial for interpreting planetary remote sensing data. Here, four mafic rocks simulating a possible Martian composition were synthesized with identical bulk chemistry but different mineralogical assemblages, from fully amorphous to ∼70 wt.% crystal content, to investigate how crystal content affects Visible and Near-Infrared (VNIR) reflectance spectra. Bi-directional VNIR reflectance was collected at room temperature across a range of incidence (0°, 30°, 60°) and emergence (−70° to +70°) angles. The diagnostic absorptions of the two most abundant phases, pyroxene and glass, are not distinguishable in the spectra and can even reproduce the spectral fingerprint of olivine, absent from the samples; only minor iron oxides (magnetite and hematite, ∼1–7 wt.%) produce clearly identifiable absorptions. Instead, spectral slope emerges as the primary proxy for the glass/crystal ratio: NIR/VNIR slope decreases systematically with increasing crystal content, driven jointly by the incorporation of iron oxides and the loss of the positive-slope contribution of residual glass. Principal Component Analysis and k-means clustering independently confirm this control, identifying three clusters that map onto the glass/crystal ratio. This decoupling indicates that the crystal content of a mafic terrain cannot be inferred from pyroxene- or glass-related absorptions alone, but rather from spectral slope and iron-oxide features. These results experimentally support previous hypotheses linking the spectral diversity of Martian mafic terrains to their degree of crystal content and oxidation state and highlight variable glass abundance as an under-considered contributor to the spectral interpretation of the Martian surface.

^1,2,3Scott M. Perl, ^2,4Aaron J. Celestian, ⁴Frank A. Corsetti
Journal of Geophysical Research: Planets 131, e2026JE009730 Link to Article [DOI: 10.1029/2026JE009730]
¹Earth, Planetary, and Space Sciences, University of California Los Angeles, Los Angeles, CA, USA
²Mineral Sciences, Los Angeles Natural History Museum, Los Angeles, CA, USA
³Blue Marble Space Institute of Science, Seattle, WA, USA
⁴Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA
Published by arrangement with John Wiley & Sons

Evaporite minerals can capture and entomb organic matter within their intercrystalline and intracrystalline structure because they precipitate relatively quickly (nomenclature adopted from Schopf et al. (2012), https://doi.org/10.1089/ast.2012.0827). Thus, evaporite minerals constitute a target for biosignature investigation on Earth and Mars, where evaporitic deposits are known to exist. However, little is known about the process of organic preservation and detection in evaporites, or the stability of such molecules when exposed to significant UV radiation as would be present on the surface of Mars. Here, we investigate the incorporation of β-carotene into halite (NaCl) by growing halite in the lab in the presence of know concentrations of β-carotene and examining the resultant precipitated crystals and fluid inclusions via Raman spectroscopy. Following brine evaporation, the experimental β-carotene-containing halite was exposed to UV-C to simulate conditions on the Martian surface. Results reveal that β-carotene has a strong Raman signature that remains intact even when entombed in halite. In particular, fluid inclusions within the halite displayed particularly strong β-carotene Raman signatures after UV-C exposure. Little change was observed even after several days of UV-C delivery. Our results reveal that complex organic molecules like β-carotene should be preserved well in halite (especially in fluid inclusions) and that halite does provide protection from organic matter degradation from UV-C radiation. Thus, evaporites constitute a good target for the search for biomarkers on Mars. These findings will allow for proper criteria for the discovery of any potential physical biosignature and chemical biomarker that would be on active ocean worlds (Europa, Enceladus) and for future Mars subsurface drilling missions.

¹S. Desikamani, ²L.D. Peterson, ¹M.E. Newcombe, ³C.M.O’D. Alexander, ³J. Wang, ¹R.D. Ash, ⁴S.G. Nielsen, ¹P.M. Piccoli, ³E.S. Bullock
Geochimica et Cosmochimica Acta, (in Press) Link to Article [DOI: 10.1016/j.gca.2026.08.024]
¹University of Maryland, College Park, MD 20742, USA
²Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
³Carnegie Institution for Science, Washington DC 20015, USA
⁴Centre de Recherches Pétrographiques et Géochimiques (CRPG – CNRS), Nancy 54501, France
Copyright Elsevier

Nucleosynthetic isotope signatures indicate that the Earth is predominantly made from inner solar system non-carbonaceous (NC) materials. However, a major uncertainty in models of water addition to the proto-Earth is the extent to which H (calculated in this study as µg/g H₂O, but present as H-bearing species) in nominally anhydrous minerals (NAMs) from NC materials could contribute to the bulk Earth water budget. The preserved water concentration of NC meteorite NAMs may also shape our understanding of processes occurring in the solar protoplanetary disk (e.g., implantation of H on the surfaces of NAM grains) and in planetesimals (e.g., metamorphism in chondrite parent bodies). Reported water contents for NAMs from the ordinary chondrites (OCs), the dominant NC material falling to Earth today, range between 10⁰-10⁴ µg/g H₂O. In order to better constrain the potential contribution of ordinary chondrites to the Earth’s water budget we have measured water concentrations in NAMs from eight equilibrated OCs, six of which have not previously been investigated for water, and two of which (Chelyabinsk and Bensour) were previously measured in other laboratories. We find that olivine and low-Ca pyroxene from equilibrated OCs contain less than ∼ 10 µg/g H₂O. Based on these measurements, the water content of the NAM fraction of equilibrated OCs is < 10 µg/g H₂O (a factor of ∼ 60–120 lower than prior estimates). Combining these constraints of equilibrated OC NAM water contents with published measurements of NAMs and glassy mesostases from unequilibrated OCs, we estimate that NAMs and glass in OC parent bodies could have delivered no more than ∼ 0.2 ocean masses of water to Earth (∼1% of an assumed total water budget of 18 ocean masses). Additional water could have been delivered from phyllosilicates and organics in the most primitive OC material that is not considered in our modeling. The difference in NAM water concentrations obtained here relative to some prior studies may be rooted in analytical artifacts associated with their nanoscale secondary ion mass spectrometric measurements.