¹Sohei Wada,¹Ken-ichi Bajo,¹Hisayoshi Yurimoto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70161]
¹Department of Earth and Planetary Sciences, Hokkaido University, Sapporo, Japan
Published by arrangement with John Wiley & Sons

The surfaces of small celestial bodies are continuously modified by spaceweathering and surface gardening, yet their interaction remains poorly understood due toobservational gaps between micrometer and centimeter scales. Here we analyzed thetwo-dimensional distribution of helium in the carbonaceous chondrite NWA 801 (CR2)using the LIMAS secondary neutral mass spectrometer with micrometer resolution. Theresults show that 4He is concentrated mainly in the fine-grained matrix, forming a distinctHe-rich network surrounding He-poor fine-grained regions. This structure suggests thatspace-weathered particles were transported into the subsurface. The process may involve agranular convection driven by impact-induced vibrations. It likely occurred during the earlysolar system on time scales of 10,000 years and at depths ranging from tens of centimetersto meters. Such mixing repeatedly exposed fresh material to solar wind irradiation,producing three-dimensional 3He-enriched deposits rather than purely surface-limitedaccumulations. These findings provide direct microstructural evidence for the dynamiccoupling between space weathering and surface gardening and highlight a potentialmechanism for forming solar wind–derived helium and hydrogen resources on small celestialbodies.