^1,2Tian Zhang, ^1,2,3Hong Tang, ^1,2,3Xiongyao Li, ^1,3Bing Mo, ¹Yuanyun Wen, ⁴Sheng Zhang, ^1,3Wen Yu, ^1,2Chuanjiao Zhou, ^1,2Haiyan Long, ^1,2,3Jianzhong Liu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.11.047]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
³CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
⁴College of Resources and Environment Engineering, Guizhou University, Guiyang 550025, China
Copyright Elsevier

The degassing of solar wind-related volatiles is thought to contribute to volatile cycling on the Moon. However, it remains uncertain which lunar minerals preferentially release them. Here, we report an unusual foamy texture found only on the surface of ilmenite crystals within a Chang’e-6 (CE-6) basalt clast. The distribution and chemical composition of this texture indicates that it results from in-situ melting of the ilmenite surface rather than from an impact-induced splash melt. Considering the evidence—including the long exposure time, presence of deep-seated planar defects, open vesicles, large spherical np-Fe⁰ particles, and a rutile-like mineral—the foamy texture is interpreted to result from the intense release of abundant solar wind-related volatiles (e.g., H/H2, He, and OH/H2O) by an impact-induced conductive heating event. Restriction of the foamy texture to the surface of ilmenite within the CE-6 basalt clast indicates that solar wind composition, especially for H-related volatiles, are released more intensely from ilmenite than from silicate minerals such as pyroxene and plagioclase. Our findings suggest that solar wind-related volatiles released from high-Ti mature regolith likely made a greater contribution to the lunar exosphere and the lunar surface volatiles, including polar deposits, relative to those from low-Ti immature regions. This has important implications for understanding volatile cycles and future in-situ resource utilization on the Moon.

^1,2Michael T. Thorpe,²Elizabeth B. Rampe,^3,4Juergen Thieme,³Eric Dooryhee,^2,5Seungyeol Lee,⁶Roy Christoffersen
American Mineralogist 110,1689-1701 Open Access Link to Article [https://doi.org/10.2138/am-2023-9290]
¹University of Maryland, NASA Goddard Space Flight Center, and CRESST II, Greenbelt, Maryland 20771, U.S.A.
²NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
³Brookhaven National Lab, NSLS-II, Upton, New York 11973, U.S.A.
⁴Institute for X-Ray Physics, Georg-August University Goettingen, Goettingen University, Göttingen 37073, Germany
⁵Department of Earth and Environmental Sciences, Chungbuk National University, Seowon-Gu, Cheongju, Chungbuk 28644, Korea
⁶Amentum JETS-II contract, NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Society of America

Mudrocks and mud-sized sediments (i.e., silt to clay) dominate the surface of Earth and Mars. These fine-grained sediments preserve a rich history of sedimentary processes from source to sink and shed light on ancient climates. However, both the physical and chemical nature of these materials make them difficult to fully characterize with traditional laboratory techniques. Here, we explore a cross-disciplinary and high-resolution approach using synchrotron radiation for X-ray diffraction, pair distribution function analysis, and submicrometer-scale X-ray fluorescence, combined with transmission electron microscopy, to better understand the nanostructure and composition of mud-sized sediments from a glacio-fluvial watershed in southwest Iceland. Our results demonstrate that sediments in the cold and wet climate of Iceland are more altered than previously thought, as evidenced by the identification of kaolinite and mixed-layer kaolinite-smectite. Additionally, sediments are enriched in amorphous materials and nanocrystalline phases, as determined from grain morphologies and compositions consistent with allophane, hisingerite, ferrihydrite, and halloysite. These alteration products are present as intimate mixtures that vary across depositional sites, demonstrating the dynamic nature of the secondary assemblage from source to sink. This work has implications for Mars, where, for example, basalt-sourced sedimentary rocks from Gale crater are abundant in clay minerals and amorphous materials. Finally, this work underpins the importance of using high-resolution techniques, a coordinated methodology, and developing innovative approaches for future planetary sample return missions (e.g., Mars sample return).