^1,2,3,4Marie J.B. Henderson,⁴Briony H.N. Horgan,⁵Samuel J. Lawrence,⁶Julie D. Stopar,⁶Lisa R. Gaddis
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115628]
¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
²Center for Space Sciences and Technology, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
³Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD 20771, USA
⁴Purdue University, West Lafayette, IN 47907, USA
⁵NASA Johnson Space Center, Houston, TX 77058, USA
⁶Lunar and Planetary Institute, Houston, TX 77058, USA
Copyright Elsevier

The Marius Hills Volcanic Complex exhibits the highest concentration of extrusive volcanic landforms on the Moon, in the form of both domes and cones. The interpretive advancements made in this investigation result from improved spectral resolution and analysis techniques. Moon Mineralogy Mapper (M3) spectral analysis shows that the rounded landforms in MHVC exhibit spectra consistent with glass, confirming a cinder cone with an explosive volcanic origin. The presence of scoria-like glass-rich pyroclasts that should be distinct from the glass beads collected during Apollo. This research provides evidence that spectroscopy can identify volcanic landforms when visible images of the morphology are inconclusive, which is essential for future exploration of volcanic terrains. The likely concurrent eruption of the domes and cones with the differences in the mineralogy of the resulting edifices (e.g., presence of glass) add supporting evidence to the hypothesis that extrinsic properties (e.g., ascent rate), not changes in magma composition (e.g., amount of volatiles), led to the different volcanic morphologies. Combining the morphology and the spectral data, we hypothesize that the magma evolution of the region was long-lived and with distinct early edifice-forming and later mare-forming episodes. The long-lived volcanism recorded in multiple volcanic units within close proximity in MHVC would be ideal for future exploration and eventual sample return.

¹Dorian Thomassin,¹Laurette Piani,¹Johan Villeneuve,²Marie-Camille Caumon,¹Nordine Bouden,¹Yves Marrocchi
Earth and Planetary Science Letters 616, 118225 Link to Article [https://doi.org/10.1016/j.epsl.2023.118225]
¹Université de Lorraine, CNRS, CRPG, UMR 7358, Nancy, France
²Université de Lorraine, GeoRessources, UMR 7359, Nancy, France
Copyright Elsevier

Due to their numerous isotopic similarities to terrestrial rocks, enstatite chondrites (ECs) are commonly proposed as Earth’s main building blocks. Although ECs contain sufficient H concentrations to account for the mass of Earth’s oceans, the physicochemical process(es) behind their H incorporation remain under constrained. Here, we combined secondary ion mass spectrometry analyses of volatile contents (H, C, F, Cl, S) and H isotopic compositions with Raman spectroscopy analyses of H speciation in the glassy mesostases of EC chondrules. EC chondrule mesostases (68–830 wt. ppm H) contain much more H than chondrule silicates (5–25 wt. ppm) and are characterized by H isotopic compositions of δD = −109 ± 27‰. Hydrogen and sulfur contents are positively correlated in EC chondrule mesostases, and we commonly observed well-resolved Raman peaks at 2580 cm−1, corresponding to HS− or H2S bonding. These results illustrate that the high H abundances in EC chondrule mesostases do not result from terrestrial contamination or secondary asteroidal processes, nor were their high volatile contents inherited from chondrule precursors. Instead, they were established at high temperature during chondrule formation via interactions between Fe-poor melts and S-rich gas under extremely reducing conditions. Our data confirm that ECs contain sufficient primordial hydrogen to explain the terrestrial water budget, and likely contributed important amounts of other volatile elements such as carbon, which was fundamental to the formation of life.