¹Yukari Yamaguchi, ¹Akiko M. Nakamura
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117005]
¹Graduate School of Science, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan
Copyright Elsevier

Hypervelocity impacts play a key role in material transport among planetary bodies. To investigate how target material properties influence high-velocity ejecta, we conducted impact experiments using aluminum projectiles at velocities of about 7 km s−1, with serpentinite, dolerite, and pyrophyllite as targets. Ejecta were impacted onto polycarbonate plates and analyzed using high-speed imaging and crater measurements. Ejecta velocities ranged from 5 to 13 km s−1, with maximum fragment sizes decreasing from 100 to 7 μm as velocity increased. Ejecta with velocities exceeding twice the particle velocity existed, consistent with previous numerical simulations. No clear differences in size–velocity or ejection angle–velocity relationships were observed among the targets. The largest sizes of high-velocity ejecta in this study may suggest that near the impact point, the material may behave as if it were in a fully cracked state. The axial ratios of the craters, which are considered to reflect those of the ejecta, were approximately 0.6–0.7. Although direct extrapolation to planetary scales is not straightforward, these results provide new experimental constraints on the influence of target properties on high-velocity ejecta production, contributing to a better understanding of material transport between planetary bodies.

^1,2Sergey N. Britvin,¹Oleg S. Vereshchagin,¹Natalia S. Vlasenko,¹Maria G. Krzhizhanovskaya,³Marina A. Ivanova,¹Irina A. Volkova
American Mineralogist 111, 335-344 ink to Article [https://doi.org/10.2138/am-2025-9851]
¹Saint Petersburg State University, Universitetskaya Nab. 7/9, 199034 St. Petersburg, Russia
²Kola Science Center, Russian Academy of Sciences, Fersman Str. 14, 184209 Apatity, Russia
³Vernadsky Institute of Geochemistry of the Russian Academy of Sciences, Kosygin St. 19, Moscow 119991, Russia
Copyright: The Mineralogical Society of America

The enigma of ammonium mineral speciation in the solar system has no proven solution due to the lack of data on the real minerals serving as space ammonium carriers. We herein report on the discovery of the first ammonium mineral in meteoritic substance and show its relevance to compositional and spectral characteristics ascribed to hypothetical ammonium phases in cometary and asteroidal bodies. Chemically distant from previously inferred volatile organics or ammoniated phyllosilicates, the mineral is an aqueous metal-ammonium sulfate related to the picromerite group—a family of so-called Tutton’s salts. Nickeloan boussingaultite, (NH4)2(Mg,Ni)(SO4)2·6H2O, was discovered in Orgueil, a primitive carbonaceous chondrite closely related to (162173) Ryugu and (101955) Bennu, the C-type asteroids. The available spectroscopic, chemical, and mineralogical data signify that natural sulfates related to boussingaultite-nickelboussingaultite series perfectly fit into the role of bound ammonia carriers under conditions of cometary nuclei and carbonaceous asteroids. The potential technogenic contamination of astromaterial samples and the difficulties in electron microprobe determination of ammonium are discussed in the context of recently published reports on the discovery of lunar and asteroidal ammonium-containing minerals.