¹Kunihiko Nishiizumi e al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701111]
¹Space Sciences Laboratory, University of California, Berkeley, Berkeley, California, USA
Published by arrangement with John Wiley & Sons

Surface processes on the asteroid Ryugu have been investigated using cosmic-ray-produced radionuclides, 10Be, 26Al, and 36Cl, and stable noble gases, on eight samples returned by the Hayabusa2 spacecraft. The 10Be and 26Al along with 21Ne measurements indicate that the two Chamber A samples A0105 collected during the first touchdown (TD) were exposed to cosmic rays for ~6.8 Myr at a shielding depth of 4–15 g cm−2. Beryllium-10 and 26Al from Chamber C samples from the second TD site, close to the artificial crater, were ejected from shielding depths of 120–160 g cm−2 for C0002, 20–85 g cm−2 for C0106-09, and 120–155 g cm−2 for C0106-10, -11, and -12, respectively. The exposure ages of these four C0106 samples differ, ranging from 1.7–8.8 Myr. These measurements provide unique and clear evidence that Hayabusa2 successfully collected subsurface samples ejected by an artificially produced crater. Chlorine-36 produced by secondary-produced thermal neutrons was observed in the samples, consistent with the high concentration of H and Cl. Helium (He) and Ne of solar wind origin were released at the lowest heating temperature of 200°C during a stepwise pyrolysis.

¹Arka P. Chatterjee, ¹Julien Allaz, ²Christian Huberb, ³Luiz F.G. Morales, ^4,5Amanda Ostwald, ¹Olivier Bachmanna
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.02.033]
¹ETH Zürich, Institute of Geochemistry and Petrology, Clausiusstrasse 25, 8092 Zurich, Switzerland
²Brown University, Earth, Environmental and Planetary Sciences, 324 Brook St., Box 1846, Providence, RI 02912, USA
³ETH Zürich, Scientific Centre for Optical and Electron Microscopy (ScopeM), Otto-Stern-Weg 3, 8093 Zurich, Switzerland
⁴Smithsonian National Museum of Natural History, 10th St. & Constitution Ave. NW, Washington, DC 20560, USA
⁵Michigan State University, Department of Earth and Environmental Sciences, 207 Natural Science Bldg, East Lansing, MI 48824, USA
Copyright Elsevier

Martian meteorites, the only available samples of Martian lithologies, provide unique insights into martian magmatism. Olivines in these meteorites contain complex phosphorus (P) zoning, which shed insights into the behaviour of mafic magmas in the martian crust. These olivines crystallized in multiple stages in ascending magmas, and preserved compositional zoning, particularly in P, due to its low diffusivity. Although previous studies have documented P zoning in martian olivines and attributed its formation to rapid crystallization events in magma storage zones within the crust, the processes responsible for the undercooling and fast olivine growth remain unresolved. This study addresses the challenge of interpreting P zoning in martian olivines to better understand the conditions which affected their crystallization histories. Using high-resolution P X-ray maps and microprobe traverses, we show that P zoning in olivine megacrysts from shergottites (martian basalts) and chassignites (martian dunites) consistently records rapid crystallization events at high undercooling due to magma ascent through the martian crust. These zoning patterns, observed in cores, mantles, and rims of olivines from hypabyssal and intrusive samples, highlight different crystallisation conditions during staging, ascent and emplacement of magmas at varying crustal depths. P zoning in olivine-phyric shergottites, viewed in the light of previous thermobarometry results, record initial olivine nucleation in the lower crust, ascent to the mid-crust and final rapid crystallization in the shallow subsurface. Similarly, we inferred multiple cycles of magma ascent and storage in the martian crust from the P zoning in poikilitic and non-poikilitic regions of a poikilitic shergottite. We also provide evidence from P zoning in olivines to differentiate between magma storage relatively deep in the crust and shallow, hypabyssal emplacement. The nature of P zoning during the final stages of olivine crystallization can serve as in-situ evidence of the eruptive behaviour of shallow magma bodies. Further analyses of available meteorites and olivines from future sample return missions will be fundamental to build a holistic model of martian magma plumbing systems and its evolution through time