The dwarf planet Vesta is helping scientists better understand the first era in the formation of our solar system. Two recent papers involving scientists at the University of California, Davis, use Vesta-derived meteorite data to solve the “missing mantle problem” and push back our knowledge of the solar system to just a few million years after the start of its formation. The articles were published in Nature Communication September 14 and Nature astronomy September 30.
Vesta is the second largest body in the asteroid belt at 500 kilometers in diameter. It is large enough to have evolved in the same way as rocky and terrestrial bodies like the Earth, Moon, and Mars. At first, they were balls of molten rock heated by collisions. Iron and siderophiles, or “iron-loving” elements such as rhenium, osmium, iridium, platinum, and palladium flowed down the center to form a metallic core, leaving the mantle poor in these elements. As the planet cooled, a thin solid crust formed on the mantle. Later, meteorites brought iron and other elements to the crust.
Most of a planet like Earth is the mantle. But mantle-type rocks are rare among asteroids and meteorites.
“If we look at meteorites, we have basic material, we have a crust, but we don’t see a mantle,” said Qing-Zhu Yin, professor of Earth and Planetary Sciences at the College of Letters and Studies. UC Davis Sciences. Planetary scientists have called this the “missing mantle problem”.
In the recent Nature Communications article, Yin and UC Davis graduate students Supratim Dey and Audrey Miller worked with first author Zoltan Vaci of the University of New Mexico to describe three recently discovered meteorites that include rock from the mantle, called ultramafics which include the mineral olivine as a major component. The UC Davis team contributed to an accurate isotope analysis, creating a fingerprint that allowed them to identify the meteorites as coming from Vesta or a very similar body.
“This is the first time that we got a taste of Vesta’s coat,” said Yin. NASA’s Dawn mission remotely observed rocks from the South Pole’s largest impact crater on Vesta in 2011, but found no mantle rock.
Probing the early solar system
Because she is so small, Vesta formed a solid crust long before larger bodies like the Earth, Moon, and Mars. Thus, the siderophilic elements that have accumulated in its crust and mantle are a record of the very beginning of the solar system after the formation of the nucleus. Over time, the collisions shattered pieces of Vesta that sometimes fall to Earth as meteorites.
The Yin lab at UC Davis had previously collaborated with an international team examining elements of the lunar crust to probe the early solar system. In the second article, published in Nature Astronomy, Meng-Hua Zhu at Macau University of Science and Technology, Yin and his colleagues extended this work using Vesta.
“Because Vesta formed very early on, it’s a good model for looking at the entire history of the solar system,” Yin said. “This takes us back to two million years after the start of the formation of the solar system.”
It was believed that Vesta and the larger inner planets may have obtained much of their material from the asteroid belt. But a key finding of the study was that the inner planets (Mercury, Venus, Earth and Moon, Mars and inner dwarf planets) derived most of their mass from collision and fusion with other large molten bodies. at the start of the solar system. The asteroid belt itself represents the material left over from the formation of the planets, but did not contribute much to the larger worlds.
Additional co-authors of the Nature Communications article are: James Day and Marine Paquet, Scripps Institute of Oceanography, UC San Diego; Karen Ziegler and Carl Agee, University of New Mexico; Rainer Bartoschewitz, Bartoschewitz Meteorite Laboratory, Gifhorn, Germany; and Andreas Pack, Georg-August-Universität, Göttingen, Germany. The other co-authors of Yin on the Nature Astronomy article are: Alessandro Morbidelli, University of Nice-Sophia Antipolis, France; Wladimir Neumann, Universität Heidelberg, Germany; James Day, Scripps Institute of Oceanography, UCSD; David Rubie, University of Bayreuth, Germany; Gregory Archer, University of Münster, Germany; Natalia Artemieva, Institute of Planetary Sciences, Tucson; Harry Becker and Kai Wünnemann, Freie Universität Berlin.
The work was supported in part by the Science and Technology Development Fund, Macau, Deutsche Forschungsgemeinschaft and NASA.