^1,2Yexin Luo,³Aicheng Zhang,¹Qing Lin,¹Xingmei Shan,¹Zhimao Du,²Mingbao Li,⁴Qi Li,⁵Xiuhong Liao,¹Shaolin Li
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009360]
¹Shanghai Astronomy Museum (branch of Shanghai Science & Technology Museum), Shanghai, China
²State KeyLaboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, China
³State KeyLaboratory of Critical Earth Material Cycling and Mineral Deposits, School of Earth Sciences and Engineering, NanjingUniversity, Nanjing, China
⁴Polar Sample Repository, MNR, Polar Research Institute of China, Shanghai, China
⁵State KeyLaboratory of Geological Processes and Mineral Resources, Gemmological Institute, China University of Geosciences,Wuhan, China
Published by arrangement with John Wiley & Sons

Ordinary chondrites, sourced from S-type asteroids, provide the most direct documentation of the thermal history of their parent bodies. Current research focuses predominantly on silicates, but early endogenic metamorphism overprinted by impact heating can yield ambiguous silicate records. In contrast, Fe-Ni metal, also as a major component, exhibits higher strain rates and greater temperature sensitivity than silicates. H-group ordinary chondrites possess the highest metal content, characterized by thermally informative complex microstructures. In this study, the Electron Backscatter Diffraction technique is employed on 14 H chondrites to constrain their thermal history. Martensite and duplex plessite, microstructures indicative of rapid cooling, are prevalent in the metal. Furthermore, characteristic microstructures formed by martensite tempering under distinct thermal pathways are observed, including polycrystalline martensite (low-temperature, prolonged heating), net plessite, and acicular plessite (higher-temperature tempering). Consequently, the metal records a rapid cooling event followed by widespread tempering and thermal annealing. This implies that the H parent body, similar to those of L chondrites, experienced a catastrophic impact, evidenced by their shared quenched metal structure. Subsequent tempering and annealing probably resulted from thermal effects in the re-accretion of impact debris.

¹Sergei V. Bykov et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009375]
¹Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA,
Published by arrangement with John Wiley & Sons

We report the in situ detection of amorphous hydrated silica in the Bills Bay abrasion patch, located in the eastern portion of the Margin Unit between the rim of Jezero crater and the western delta. Here, hydrated silica co-occurs with olivine, Fe-Mg carbonates, secondary Fe-Mg silicates, and hydrated Mg-sulfate as determined by UV Raman (SHERLOC) and X-ray fluorescence (PIXL) spectrometers onboard the Perseverance rover. Almost pure hydrated silica fills the intergranular space between olivine and carbonate-bearing domains. We performed Raman analysis of terrestrial opals with various crystallinities including opal-AN, AG, CT, and C. We found that the Si−O symmetric stretching Raman band at ∼800 cm−1 is sensitive to opal crystallinity, yet insensitive to ambient temperature (at ∼77–293 K) and silica hydration. We identified the crystal structure of the Bills Bay Hydrated Silica (BBHS) as opal-A. Furthermore, we developed a Raman methodology to quantify opal-A hydration. We found that the total amount of hydration in the BBHS phases was 1.7 ± 0.2 wt. %. Most of this hydration, 1.5 ± 0.2 wt. %, reflects the presence of silanol groups. Our analysis revealed that the Raman spectrum of BBHS closely resembles that of opal-A that has lost most of its molecular water. The composition and textures of the Bills Bay abrasion indicate that BBHS is derived from olivine carbonation. Opal-A is the only silica polymorph identified in the SHERLOC data. We hypothesized that silica precipitation occurred, either during the late stages of a major carbonation event or during a brief, subsequent aqueous alteration event unrelated to carbonation.