The dwarf planet Vesta, a window into the early solar system

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 our knowledge of the solar system back to just a few million years after its beginning. training. 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 similarly to rocky 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 have sunk to the center to form a metallic core, leaving the mantle deficient 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 the bulk of a planet like Earth is made up of mantle. But mantle-like rocks are rare among asteroids and meteorites.

“If we look at meteorites, we have a base material, we have a crust, but we don’t see a mantle,” said Qing-Zhu Yin, a professor of earth and planetary sciences at UC Davis College. of Letters and Science. Planetary scientists have called this the “missing mantle problem”.

In the recent Nature Communications paper, Yin and UC Davis graduate students Supratim Dey and Audrey Miller worked with first author Zoltan Vaci at the University of New Mexico to describe three recently discovered meteorites that include mantle rock, called ultramafics which include the mineral olivine as a major component. The UC Davis team helped with precise 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 we got to taste Vesta’s coat,” Yin said. NASA’s Dawn mission remotely observed rocks from the largest south pole impact crater on Vesta in 2011, but found no mantle rock.

Probing the Early Solar System

Because it’s so small, Vesta formed a solid crust long before larger bodies like the Earth, Moon, and Mars. Thus, the siderophile elements that have accumulated in its crust and mantle form a record of the very first solar system after the formation of the core. Over time, the collisions shattered pieces of Vesta which sometimes fall to Earth as meteorites.

Yin’s lab at UC Davis previously collaborated with an international team examining elements of the lunar crust to probe the early solar system. In the second paper, published in Nature Astronomy, Meng-Hua Zhu of Macau University of Science and Technology, Yin and his colleagues extended this work using Vesta.

“Because Vesta formed very early, it’s a good model to look at the whole history of the solar system,” Yin said. “That takes us back to two million years after the solar system began to form.”

It had been thought that Vesta and the larger inner planets could 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 the inner dwarf planets) derive most of their mass from collision and merger with other large bodies in fusion at the beginning of the solar system. The asteroid belt itself represents the remnant material of planet formation, but has not contributed much to the larger worlds.

Additional co-authors on the Nature Communication paper 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. Yin’s other co-authors on the Nature Astronomy paper 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 partly funded by the Macau Science and Technology Development Fund, Deutsche Forschungsgemeinschaft and NASA.

Arline J. Mercier