The early solar system was more donut than target

June 20 () –

The planetary disk of our solar system was initially more shaped like a donut than a target, as in our time, reveals a new research on iron meteorites.

Iron meteorites are remains of the metallic cores of the first asteroids in our solar system. Iron meteorites contain refractory metals, such as iridium and platinum, that formed near the Sun but were transported to the outer solar system.

The new study, led by scientists from the University of California Los Angeles (UCLA) and the Johns Hopkins University Applied Physics Laboratoryshows that for this to have happened, the protoplanetary disk of our solar system had to have been donut-shaped because refractory metals could not have crossed the large gaps in a target-shaped disk of concentric rings.

The article, published in Proceedings of the National Academy of Sciencessuggests that refractory metals moved outward as the protoplanetary disk expanded rapidly and were trapped in the outer solar system by Jupiter.

Researchers maintain that refractory metals, which condense at high temperatures, such as iridium and platinum, They were most abundant in meteorites formed in the outer disk, which was cold and far from the sun. These metals should have formed near the sun, where the temperature was much higher. Was there a pathway that moved these metals from the inner disk to the outside?

Most meteorites formed in the first few million years of the history of the solar system. Some meteorites, called chondrites, are unmolten conglomerates of grains and dust left over from the formation of planets. Other meteorites experienced enough heat to melt while their parent asteroids were forming. When these asteroids melted, the silicate part and the metallic part separated due to their difference in density, similar to how water and oil don’t mix.

Today, most asteroids are located in a thick belt between Mars and Jupiter. Scientists believe that Jupiter’s gravity altered the course of these asteroids, causing many of them to collide with each other and break up. When fragments of these asteroids fall to Earth and are recovered, they are called meteorites.

Iron meteorites come from the metal cores of the first asteroids, older than any other rock or celestial object in our solar system. Irons contain isotopes of molybdenum that point to many different locations throughout the protoplanetary disk in which these meteorites formed. That allows scientists to learn what the chemical composition of the disk was like in its infancy.

Previous research with the Atacama Large Millimeter/submillimeter Array in Chile has found many disks around other stars that resemble concentric rings, like a dart board. The rings of these planetary disks, like HL Tau, are separated by physical gaps, so this type of disk could not provide a route to transport these refractory metals from the inner disk to the outside.

The new paper argues that our solar disk probably did not have a ring structure in the beginning. Instead, our planetary disk looked more like a doughnut, and asteroids with metal grains rich in iridium and platinum metals They migrated to the outer disk as it expanded rapidly.

But that confronted researchers with another puzzle. After the disk expanded, gravity should have pulled these metals back to the sun. But that didn’t happen.

“Once Jupiter formed, it most likely opened a physical gap that trapped the metals iridium and platinum in the outer disk and prevented them from falling into the sun,” he said. it’s a statement first author Bidong Zhang, a planetary scientist at UCLA. “These metals were later incorporated into asteroids that formed in the outer disk. This explains why meteorites formed in the outer disk (carbonaceous chondrites and carbonaceous-type iron meteorites) have much higher iridium and platinum contents than their inner disc peers.”

Zhang and his collaborators previously used iron meteorites to reconstruct how water was distributed in the protoplanetary disk.

“Iron meteorites are hidden gems. “The more we learn about iron meteorites, the more we unravel the mystery of the birth of our solar system,” Zhang said.