¹Chunjie Cao,¹Duojun Wang,¹Kenan Han,¹Kewei Shen,¹Kexuan Zhang
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009722]

¹High Pressure Sciences Experiment Center, College of Earth and Planetary Sciences, University of Chinese Academy ofSciences, Beijing, China
Published by arrangement with John Wiley & Sons

The vesicles of meteorite fusion crusts offer a key window into transient processes during atmospheric entry, yet their formation mechanisms remain poorly constrained. In this study, we investigated the morphology, mineralogical composition, and evolutionary mechanisms of vesicles in the fusion crust and primary lithology of the meteorite NWA 10645 using micro-CT as the primary technique, complemented by SEM–EDS petrography. Vesicle nucleation in the fusion crust was likely driven by volatile supersaturation generated from multiple reservoirs, including apatite, pyroxene, melt inclusions, and mesostasis. After nucleation triggered by apatite devolatilization, isolated vesicles continued to grow and underwent three evolutionary stages: early growth, aggregation, coalescence, and critical rupture. Micro-CT 3D imaging shows that adjacent nucleated vesicles rapidly aggregated within a short time, forming bead-like alignments, then gradually coalesced into larger pores, and evolved into ellipsoidal shapes due to inertial tensile forces generated in the melt during high-velocity atmospheric entry, while near-surface vesicles approached critical rupture. Furthermore, Classical Nucleation Theory (CNT) is applied for the first time to predict a minimum nucleation radius of 23–70 nm, significantly smaller than the vesicle sizes resolved by micro-CT and SEM. This result indicates that vesicle nucleation occurs at a transient nanoscale stage. Diffusion-length estimates further suggest that volatile transport in the melt could support subsequent vesicle growth to experimentally observable micron-scale sizes.

¹J. R. Hill,¹P. R. Christensen
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2026JE009775]
¹School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

Martian chloride salt deposits were first identified by Osterloo et al. (2008, https://doi.org/10.1126/science.1150690) and surveyed by Osterloo et al. (2010, https://doi.org/10.1029/2010je003613) primarily using thermal infrared data acquired by the Thermal Emission Imaging System (THEMIS) onboard the 2001 Mars Odyssey spacecraft. Over the subsequent 15 years, the THEMIS instrument has greatly expanded its areal and repeat coverage of the Martian surface. A principal component-based index was also developed to identify chloride salts and quantify the confidence level of their detection. Pairing the expanded data set with this improved analytical technique enabled a more accurate global survey of chloride salts, which identified 1,605 distinct deposits covering 11,974 km2. This includes 777 newly identified deposits, which represents a ∼20% increase in the surface area (∼1,997 km2) of identified chloride salts. The chloride salt deposits are primarily associated with Noachian-aged terrains, with a significant percentage occurring in Early Noachian terrains. A steep drop-off in chloride deposit occurrence was observed at the Noachian-Hesperian boundary. This pushes the period of chloride salt formation and deposition back to the earliest periods of Martian history, when the planet more closely resembled the Earth at the same time.