Introduction: Due to the relatively low closure temperature of feldspar, Ar-Ar ages of shocked meteorites typically record the age of an impact, not the formation age. Ar-Ar dating of lunar rocks has shown an increase in the impact rate around 3.9Ga [1], and many eucrites [2] and H chondrites [3] give similar ages, but with a larger spread than in the lunar case. Although only a small number of...

On April 23rd, 2019, the Aguas Zarcas meteorite fall occurred in Costa Rica. Because was quickly recovered, it contains valuable extraterrestrial materials that have not been contaminated by terrestrial processes. Our X-ray computed tomography (XCT) and scanning electron microscopy (SEM) results on various pre-rain fragments from earlier work (Kerraouch et al., 2020; 2021) revealed several dist...

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SHOCKED SIXIANGKOU L6 CHONDRITE: FURTHER CONSTRAINTS ON CONDITIONS OF SHOCK METAMORPHISM. A. Zhang , W. Hsu, R. Wang, and M. Ding, 1 Laboratory for Astrochemistry and Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China, [email protected], [email protected], [email protected], 2 State Key Laboratory for Mineral Deposits Research and Department of Ea...

Introduction: Fine-grained matrix is a major (and thermally the most primitive) component in chondrites. Analyses of chondrite matrix [1] reveal that it does not have a primordial CI-like composition, showing instead a consistent depletion compared to solar in all chondrite groups (except CI). This suggests that volatile depletion was an early event, possibly involving cooling of a hot inner di...

Electron microprobe analyses of an extraordinarily large metal grain from the Murchison type 2 carbonaceous chondrite gave 0.24 mole percent silicon. Thermodynamic calculations show that this is a natural consequence of condensation of alloys from the solar nebular gas at a total pressure l0(-5) less, similar P(tot) < l0(-3) atmosphere, provided they failed to equilibrate with it after cooling ...

Introduction: We previously determined that ~10 µm interplanetary dust particles (IDPs) collected from the Earth's stratosphere are enriched in many moderately volatile elements by a factor of ~3 over the CI meteorites [1]. However, these IDP measurements provide no direct constraint on the bulk chemical composition of the parent body (or parent bodies) of the IDPs. Collisions are believed to b...

New W isotope data for lunar metals demonstrate that the Moon formed late in isotopic equilibrium with the bulk silicate Earth (BSE). On this basis, lunar Sr isotope data are used to define the former composition of the Earth and hence the Rb-Sr age of the Moon, which is 4.48+/-0.02Ga, or 70-110Ma (million years) after the start of the Solar System. This age is significantly later than had been...