Vesta lies in the asteroid belt, between Mars and Jupiter, which is a historical relic. It preserves the processes of planetary formation, frozen in time.
Dr. Yi-Jen Lai of the Macquarie University Planetary Research Centre and Macquarie GeoAnalytical and her colleagues propose a new evolutionary history of Vesta involving a giant impact.
Researchers have published their work in a paper in Nature Geoscience.
Vesta is the second largest asteroid, after Ceres, in the asteroid belt. This cosmic rock is an ancient relic that can definitely help us better understand the origin and formation of planets.
NASA’s Dawn mission has mapped the surface of Vesta revealing an unusually thick crust at the south pole.
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So, the researchers have recently proposed a new evolutionary history of Vesta involving a giant impact. They have based their proposition on precise age determinations of zircon crystals from mesosiderites, a type of enigmatic Vestan meteorite. This sheds some light on past uncertainties about the evolution of Vesta.
Mesosiderites are a type of stony-iron meteorite, consisting of crust and molten core materials from an asteroid/asteroids. These rare meteorites give unique insights into the catastrophic break-up of differentiated (layered) asteroids, most likely Vesta.
“The major challenge is that fewer than 10 zircon grains favorable for age dating had been reported over a few decades. We developed a new method for finding zircons in mesosiderites and eventually prepared enough grains for this study,” said lead author, Dr. Makiko Haba of Tokyo Institute of Technology.
The team carried out high-precision dating using the uranium and lead isotopes of two dozen zircons in mesosiderites at the world’s leading geoscience research university, the ETH Zurich in Switzerland.
“We discovered two significant dates: 4,558.5 and 4,525.39 million years ago, that relate to the initial crust formation and metal-silicate mixing caused by a cosmic hit-and-run collision,” said Macquarie’s Dr. Yi-Jen Lai.
The team suggests that after Vesta had already differentiated into distinct crust, mantle and core layers, another asteroid about one-tenth Vesta’s size smashed into it. Therefore, causing the big disruption of the northern hemisphere. Most of the debris got stuck onto the southern hemisphere of Vesta. So, this explains the unusually thick crust that NASA’s Dawn spacecraft detected at Vesta’s south pole.
The new model also explains Vesta’s distinctive shape and the lack of the mantle mineral olivine in the Vestan meteorites.