^1,2Camilla Cioria,^1,2Giuseppe Mitri,³James Alexander Denis Connolly,⁴Jean-Philippe Perrillat,⁵Fabrizio Saracino
Journal of Geophysical Research (Planets) Link to Article [https://doi.org/10.1029/2023JE008234]
¹International Research School of Planetary Sciences, Università d’Annunzio, Pescara, Italy
²Dipartimento di Ingegneria e Geologia, Università d’Annunzio, Pescara, Italy
³Department of Earth Sciences, Institute for Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
⁴Laboratoire de Géologie de Lyon, CNRS, Université de Lyon, Université Lyon 1, Ens de Lyon, Villeurbanne, France
⁵Department of Geology, University of Liège, Liège, Belgium
Published by arrangement with John Wiley & Sons

The mineralogy of planetary mantles formed under reducing conditions, as documented in the inner regions of the solar system, is not well constrained. We present thermodynamic models of mineral assemblages that would constitute the mantles of exo-Mercuries. We investigated reduced materials such as enstatite chondrites, CH, and CB chondrites, and aubrites, as precursor bulk compositions in phase equilibrium modeling. The resulting isochemical phase diagram sections indicate that dominant phases in these reduced mantles would be pyroxenes rather than olivine, contrasting with the olivine-rich mantles found within Earth, Mars, and Venus. The pyroxene abundances in the modeled mantles assemblages depend on the silica content shown by precursor materials. The silica abundance in the mantle is closely related to Si abundance in the core, particularly in reduced environments. In addition, we propose that pyroxene-rich mantles exhibit more vigorous convective and tectonic activity than olivine-rich mantles, given that pyroxene-rich mantles would have lower viscosity and a lower solidus temperature (Ts).

^1,2Chen Li,^1,3Yang Li,²Kuixian Wei,^1,4huang Guo,⁴Rui Li,^1,3Xiongyao Li,^1,3Jianzhong Liu²Wenhui Ma
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.06.038]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China
³Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei 230026, China
⁴Institute of Remote Sensing and Geographical Information System, School of Earth and Space Sciences, Peking University, Beijing 100871, China
Copyright Elsevier

Lunar soil undergoes space weathering and accumulates optically active opaque particles (OAOpq) of different sizes, resulting in a darkening or red shift of the reflectance spectrum. The surfaces of weakly weathered objects exhibit spectral characteristics of strong weathering; these mechanisms are still unclear. The causes of OAOpq in lunar soil are complex, especially for submicrometer particles, which account for the largest mass proportion. We found ubiquitous impact-dispersed Fe–Fe1-xS core–shell particles in Chang’e-5 lunar soil impact glass and splatter. The crystal structure, particle size distribution, and chemical composition of OAOpq in the impact glass indicate that these OAOpq consist of sulfides or metals from multiple sources. Thermodynamic evidence, diffusion behavior, and particle dispersion characteristics indicate that impact dispersion is the most likely formation mechanism of these OAOpq. The proposed impact dispersion provides a reason for the large number of OAOpq and the limited products for in situ reactions. This process explains why lunar soil with a low degree of weathering exhibits substantial spectral modification properties. The results provide insights into space weathering of the lunar surface and also imply that impact-dispersed OAOpq may be the primary modification type on asteroid surfaces. The unique chemical properties of Fe–Fe1-xS OAOpq also indicate that the lunar regolith has the potential for resource utilization.