¹Hunter Vannier,¹Briony Horgan,²Julie D. Stopar,^3,4,5Marie Henderson
Journal of Geophysical Researhc (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008108]
¹Purdue University, West Lafayette, IN, USA
²Lunar and Planetary Institute, USRA, Houston, TX, USA
³Center for Space Sciences and Technology, University of Maryland, Baltimore, MD, USA
⁴Solar System Exploration Division, NASA/GSFC, Greenbelt, MD, USA
⁵Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD, USA
Published by arrangement with John Wiley & Sons

Irregular mare patches (IMPs) are enigmatic volcanic features on the Moon’s surface, whose lack of cratering and crisp appearance imply they formed <100 Ma ago, ∼1 Ga after the expected turnoff of lunar volcanism. Multiple contrasting formation hypotheses have been put forth to explain their young appearance, including recent emplacement via eruptions of juvenile volcanic material or outgassing, versus ancient volcanic deposits that were emplaced billions of years ago but only appeared young due to highly porous material. If IMPs formed recently, this would require a reinterpretation of lunar thermal evolution. To help constrain formation hypotheses, we provide a comprehensive mineralogical analysis of IMPs using visible to near infrared hyperspectral data from the Moon Mineralogy Mapper. IMPs appear spectrally dominated by high-calcium pyroxene and are spectrally similar to their host mare and fresh craters. IMPs do not show clear indications of significant glass, implying that pyroclastic eruption was not significant in IMP formation. Based on spectral comparisons to terrestrial magma foam, we find that this also contradicts the glassiness expected for a magma foam exposed at the surface. Thus, we find it is unlikely that IMPs are composed of recently erupted material and may instead be the result of recent or ongoing surface modification of materials similar in composition and likely contemporaneously emplaced with the mare. We favor previous hypotheses that collapse processes or drainage into subsurface voids or porous materials may have been the major drivers of IMP surface rejuvenation, supported by their proximity to collapse features.

^1,2Eloy Peña-Asensio,^2,3Josep M. Trigo-Rodríguez,^4,5Jordi Sort,⁶Jordi Ibáñez-Insa,¹Albert Rimola
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14148]
¹Departament de Química, Universitat Autònoma de Barcelona, Barcelona, Spain
²Institut de Ciències de l’Espai (ICE, CSIC) Campus UAB, Cerdanyola del Vallès, Spain
³Institut d’Estudis Espacials de Catalunya (IEEC), Barcelona, Spain
⁴Departament de Física, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
⁵Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
⁶Geosciences Barcelona (GEO3BCN-CSIC), Barcelona, Spain
Published by arrangement with John Wiley & Sons

This study analyzes the mechanical and elemental properties of lunar meteorites DHOFAR 1084, JAH 838, NWA 11444, and HED meteorite NWA 6013. Utilizing microscale rock mechanics experiments, that is, nanoindentation testing, this research reveals significant heterogeneity in both mechanical and elemental attributes across the mineral samples. Olivines, pyroxene, feldspar, and spinel demonstrate similar compositional and mechanical characteristics. Conversely, other silicate and oxide minerals display variations in their mechanical properties. Terrestrial olivines subjected to nanoindentation tests exhibit increased hardness and a higher Young’s modulus than their lunar counterparts. A linear correlation is observed between the H/Er ratio and both plastic and elastic energies. Additionally, the alignment of mineral phases along a constant H/Er ratio suggests variations in local porosity. This study also highlights the need for further research focusing on porosity, phase insertions within the matrix, and structural orientations to refine our understanding of these mechanical characteristics. The findings have direct implications for in situ resource utilization strategies and future state-of-the-art impact models. This comprehensive characterization serves as a foundational resource for future research efforts in space science and mining.