¹E. Palomba,¹E. D’Aversa,^2,3T. M. Sato,^1,4A. Longobardo,¹F. Dirri,^5,6S. Aoki,⁷G. Orton,¹G. Sindoni,¹F. Oliva,¹G. Carrozzo,⁸Y. Kasaba
The Astrophysical Journal, Letters 882, L22 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab339e]
¹INAF-IAPS, via del Fosso del Cavaliere 100, I-00133 Rome, Italy
²ISAS-JAXA, Sagamihara, Kanagawa 252-5210, Japan
³Hokkaido Information University, Ebetsu, Hokkaido 069-8585, Japan
⁴DIST-Università Parthenope, Centro Direzionale Isola C4, 80143, Naples, Italy
⁵Planetary Aeronomy, Royal Belgian Institute for Space Aeronomy, 3 av. Circulaire, B-1180 Brussels, Belgium
⁶Fonds National de la Recherche Scientifique, rue d’Egmont 5, B-1000 Brussels, Belgium
⁷NASA/Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁸Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japan

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^1,2Lionel G. Vacher,¹Maxime Piralla,³Matthieu Gounelle,⁴⁵Martin Bizzarro,¹Yves Marrocchi
The Astrophysical Journal, Letters 882, L20 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab3bd0]
¹CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre les Nancy, F-54501, France
²Department of Physics, Washington University, St. Louis, MO, USA
³IMPMC, MNHN, UPMC, UMR CNRS 7590, 61 rue Buffon, F-75005 Paris, France
⁴Centre for Star and Planet Formation and Natural History Museum of Denmark, University of Copenhagen, DK-1350 Copenhagen, Denmark

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^1,2K. J. Mathew,¹K. Marti
The Astrophysical Journal, Letters 882, L17 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab357b]
¹Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
²Actinide Analytical Chemistry, Los Alamos National Lab, MS G740, Los Alamos, NM 87545, USA

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^1,2Shiyong Liao,¹Weibiao Hsu,¹Ying Wang,¹Ye Li,²Chipui Tang,²Bao Mei
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13408]
¹CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Nanjing, 210034 China
²State Key Laboratory for Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau
Published by arrangement with John Wiley & Sons

Eucrites represent one of the major lithologies of the Vestan upper crust, which had experienced pervasive and intense thermal metamorphism. To better constrain the timing and mechanism of thermal metamorphism, we carried out in situ Pb‐isotope analysis of an unbrecciated basaltic eucrite NWA 6594 on the basis of detailed mineralogical and petrographic investigations. Zircon Pb‐Pb dating reveals that NWA 6594 emplaced before or at 4547 ± 11 Ma (95% confidence, MSWD = 1.3). Studies of silica minerals indicate that NWA 6594 had experienced intense thermal metamorphism after emplacement, followed by a late impact reheating and rapid cooling. Apatite grains yield a weighted mean Pb‐Pb age of 4523 ± 2 Ma (95% confidence, MSWD = 0.76). This age could not be attributed to slow cooling after the initial crystallization, but most likely related to an independent thermal event that induced thermal metamorphism. The protracted time lag (~24 ± 13 Myr) between zircon and apatite closure ages indicates that this thermal event is most probably induced by an intense impact event that was synchronous with the metal–silicate mixing event recorded by mesosiderites. HEDs may have experienced multiple stages of thermal metamorphism after emplacement. The late impact reheating occurred after thermal metamorphism, which caused crystallization of tridymite.