^1,2Zhi Cao et al. (>10)
Earth and Planetary Science Letters 658, 119327 Link to Article [https://doi.org/10.1016/j.epsl.2025.119327]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China
²Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-Sen University, 519082 Zhuhai, China
Copyright Elsevier

The space weathering processes modify the microstructure and physicochemical properties of the surface of regolith mineral grains. We report microcraters and space-weathered rims on the surface of plagioclase, pyroxene, olivine, ilmenite and troilite grains in Chang’e-5 scooped lunar soil by electron microscopy. Micro-analysis shows that low-speed secondary impact events indicated by microcraters dominated the evolution of Chang’e-5 regolith materials, which may have driven the formation of a potential microscale redox environment under a special mineral combination. Solar wind and cosmic ray irradiation lead to significant differences in space-weathered rims of mineral surfaces. This indicates the correlation between the nature of different space-weathered rims and the inherent structure and composition of minerals. According to the statistical correlation between space-weathered rim width and track density, the average exposure ages of plagioclase and olivine in Chang’e-5 lunar soil are 2.180−0.222+0.229 Ma and 0.842−0.469+1.120 Ma, respectively. This rule applies to regolith materials with short exposure time. The in situ mineralogical evidence clarifies that compared with Apollo mature lunar soil, Chang’e-5 lunar soil seems to have undergone weaker space weathering modification and shorter exposure history, and the essence is a weakly space-weathered lunar soil from young basalt. The nature of the space-weathered rims on the mineral surface of Chang’e-5 lunar soil reflects the response of regolith material to space weathering in a short exposure history, which is of great significance for the interpretation of spectral data of returned samples.

¹Nancy L. Chabot,^1,2Colin D. Hamill,¹Evangela E. Shread,³Richard D. Ash,⁴Catherine M. Corrigan
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14341]
¹Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
²American Astronomical Society, Washington, DC, USA
³Department of Geology, University of Maryland, College Park, Maryland, USA
⁴Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
Published by arrangement with John Wiley & Sons

Troilite is a common phase in iron meteorites, but there are limited data available for the partitioning behavior of elements between troilite and solid metal. In this study, we present the results of experiments with coexisting Fe-Ni solid metal, an S-rich metallic liquid, and troilite, conducted at 800–925°C in evacuated silica tubes at 1 atm. We report solid metal–troilite partition coefficients for 22 elements commonly studied in iron meteorites. We find that elements with chalcophile behavior have an affinity for troilite and that the majority of siderophile elements are incompatible in troilite. A notable exception to this generalization is for the siderophile element Mo, which partitions roughly equally between solid metal and troilite. We find that Ni and Co are largely concentrated in the solid metal, but given their higher concentrations in iron meteorites, their partitioning behavior indicates that measurable amounts of Ni and Co should be present in iron meteorite troilite when it forms. Our work motivates the need for additional measurements of the trace element composition of iron meteorite troilite and validates the assumption made in iron meteorite crystallization models that partitioning into troilite can be neglected for the majority of siderophile elements, with the exception of Mo.