Mesosiderite formation on asteroid 4 Vesta by a hit-and-run collision

• Published in: Nature geoscience 2019-07, Vol.12 (7), p.510-515
• Main Authors: Haba, Makiko K., Wotzlaw, Jörn-Frederik, Lai, Yi-Jen, Yamaguchi, Akira, Schönbächler, Maria
• Format: Article
• Language: English
• Subjects: 704/445/209; 704/445/3928; 704/445/848; 704/445/849; Asteroid destruction; Asteroids; Dilution; Disruption; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Geochemistry; Geology; Geophysics/Geodesy; Heating; Heavy metals; Hit & run accidents; Ionization; Iron; Iron meteorites; Isotope dilution; Isotopes; Lead; Mass spectrometry; Mass spectroscopy; Meteorites; Meteors & meteorites; Olivine; Silicates; Solar system; Stony-iron meteorites; Uranium; Vesta asteroid
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/s41561-019-0377-8

Collision and disruption processes of protoplanetary bodies in the early Solar System are key to understanding the genesis of diverse types of main-belt asteroids. Mesosiderites are stony-iron meteorites that formed by the mixing of howardite–eucrite–diogenite-like crust and molten core materials and provide unique insights into the catastrophic break-up of differentiated asteroids. However, the enigmatic formation process and the poorly constrained timing of metal–silicate mixing complicate the assignment to potential parent bodies. Here we report the high-precision uranium–lead dating of mesosiderite zircons by isotope dilution thermal ionization mass spectrometry to reveal an initial crust formation 4,558.5 ± 2.1 million years ago and metal–silicate mixing at 4,525.39 ± 0.85 million years ago. The two distinct ages coincide with the timing of the crust formation and a large-scale reheating event on the eucrite parent body, probably the asteroid Vesta. This chronological coincidence corroborates that Vesta is the parent body of mesosiderite silicates. Mesosiderite formation on Vesta can be explained by a hit-and-run collision 4,525.4 million years ago that caused the thick crust observed by NASA’s Dawn mission and explains the missing olivine in mesosiderites, howardite–eucrite–diogenite meteorites and vestoids. Mesosiderite meteorites may originate from a hit-and-run impact on the parent asteroid of eucrite meteorites (probably Vesta), as mesosiderite zircon U–Pb ages are found to coincide with those for eucrites.