In the vast archive of cosmic history, iron meteorites are like ancient textbooks, jealously guarding ancient knowledge. Primordial, I dare say. Reading their metallic "pages", now, scientists have made a surprising discovery about the original shape of our Solar System, and more precisely of its protoplanetary disk.
The research, published in Proceedings of the National Academy of Sciences (I link it to you here), demonstrates once again how the study of meteorites can reveal fundamental secrets about the history of our Solar System.
Yes, but what is a protoplanetary disk?
Before delving into the discovery, it is important to understand what a protoplanetary disk is. It is a disk of gas and dust surrounding a young star in formation. It is from this disk that the planets, asteroids and comets of a star system are born.
Ours too solar system he had one. The formation of the solar system began about 4,6 billion years ago with the collapse of a giant molecular cloud: most of the mass of the cloud gathered in the center, forming the Sun, while the rest of the material flattened into a protoplanetary disk. This disk contained gas and dust that coalesced to form the planets, moons, asteroids and other bodies of the solar system.
A new vision of the protoplanetary disk
A recent study conducted by a team of scientists led by Dr. Bidong Zhang from the University of California, Los Angeles, suggests that the initial shape of the Solar System was significantly different than previously thought. Instead of a flat disk, the protoplanetary disk would have had a toroidal, doughnut-like shape.
The key to this discovery lies in the composition of iron meteorites from the outer Solar System. These meteorites contain a surprisingly large amount of refractory metals, such as platinum and iridium. All elements that typically form in high-temperature environments, near a nascent star.
The presence of these metals in meteorites from the outer Solar System has posed a puzzle to scientists. How did these materials, formed near the Sun, reach the outer regions of the Solar System? The answer, according to Zhang and his colleagues, lies precisely in the initial shape of the protoplanetary disk.
The toroidal model
The team developed models demonstrating how a toroidal shape of the protoplanetary disk would have allowed these metal-rich materials to migrate outward. In a traditional flat disk, this migration would have been much more difficult, if not impossible.
According to the study, the formation of Jupiter played a crucial role in this process. Zhang explains:
Once Jupiter formed, it most likely opened a physical gap that trapped iridium and platinum in the outer disk, preventing them from falling into the Sun.
Why it is important
Confirmation of this model would change our understanding of the history of the Solar System, with important implications also for the study of planetary formation in general. It could help astronomers better interpret observations of other forming planetary systems.
In the coming years, expect further revelations that could improve our understanding of the universe and its planetary formation processes.
It is worth saying that this new theory does not completely refute the traditional model of the flat protoplanetary disk: the authors point out that the toroidal shape would have been only an initial phase, with the disk then flattening over time.
