¹A. Nakamura,¹M. Miyahara,^2,3H. Suga,⁴A. Yamaguchi,⁵D. Wakabayashi,⁵S. Yamashita,^5,6Y. Takeichi,¹K. Kukihara,²Y. Takahashi,⁷E. Ohtani
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2023JE007951]

¹Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Japan
²Department of Earth and Planetary, Graduate School of Science, The University of Tokyo, Tokyo, Japan
³Japan Synchrotron Radiation Research Institute, Hyogo, Japan
⁴National Institute of Polar Research, Tokyo, Japan
⁵Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Japan
⁶School of Engineering, Osaka University, Osaka, Japan
⁷Department of Earth Sciences, Graduate School of Science, Tohoku University, Sendai, Japan
Published by arrangement with John Wiley & Sons

Alteration minerals in one of the Martian meteorite nakhlites, Yamato (Y) 000802, were studied to understand the alteration process and conditions. Mn-precipitates are discovered between altered plagioclase grains in Y 000802. Mn-precipitates consist of hausmannite (), manganite (γ-Mn³⁺OOH), rhodochrosite (Mn²⁺CO₃), and a trace amount of Mn⁴⁺O₂ mineral. Jarosite ) is also found. Mn²⁺ dissolved from olivine contributes to the formation of Mn-precipitates. A weakly acidic-neutral fluid containing a trace amount of  altered the olivine, and Mn²⁺ was dissolved into the fluid. The fluid also reacted with plagioclase and probably induced dealkalization of plagioclase, causing a local strong alkaline environment. Plagioclase was altered to ferroan saponite-nontronite + amorphous SiO₂ under alkaline conditions. Simultaneously, Mn^2+/3+-precipitates were formed from the Mn²⁺-containing fluid in the interstices between the altered plagioclase grains under the strong alkaline reducing environment. These alterations occurred in the deep part of the nakhlite body, where they are isolated from Martian subsurface water, including strong oxidants. The formation of Mn^2+/3+-precipitates may have been triggered by the melting of permafrost caused by an impact event around ∼633 Ma. Later, the nakhlite body was probably excavated by another impact, making it susceptible to water including strong oxidants. Pyrrhotite was dissolved and a highly acidic oxidizing fluid was formed, which would induce the formation of jarosite and the Mn⁴⁺O₂ mineral between ∼633 Ma and ∼11 Ma.

¹R. Ravichandran,¹S. Loehle,¹F. Hufgard,¹D. Leiser,⁴F. Zander,⁵L. Ferrière,²J. Vaubaillon,³P. Matlovič,³J. Tóth
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115818]
¹High Enthalpy Flow Diagnostics Group, Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 29, 70569 Stuttgart, Germany
²IMCCE, Observatoire de Paris, PSL, 77 Av. Denfert Rochereau, Paris, 75014, France
³Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia
⁴Institute of Advanced Engineering and Space Sciences, University of Southern Queensland, Toowoomba 4350, Queensland, Australia
⁵Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria
Copyright Elsevier

Optical emission spectra between 522-580 nm of ablating meteorites have been recorded at frame rates as high as 1 kHz for the first time during ground testing with simultaneous spatial and temporal resolution. A novel high frame rate emission spectroscopy arrangement has been developed and employed to diagnose the ablating meteorites in several experimental campaigns. In addition to the identification of species from emission lines detected, the resulting high-speed spectral data were used to study the temporal and spatial evolution of melting droplets and the associated spectral signatures. The time history of radiance from the atomic species emission was used to interpret the fragmentation behavior of various meteorites. Chelyabinsk meteorite exhibit almost constant radiance over time indicating steady droplet detachment whereas Ragland meteorite shows infrequent radiance peaks corresponding to random fragmentation/droplet detachment of varying sizes. A gradual rise in radiance history from iron meteorite Mount Joy shows that it takes finite time for melting and accumulation of droplets.