Earth may have formed from two separate rings around the sun
Models suggest something is wrong with our picture of the early solar system
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The inner solar system may have formed differently than we long thought. For decades, researchers thought the rocky planets formed from a single disk of dust and debris in the early solar system, but new simulations indicate there may have been two separate disks of material.
Models with a single disk or ring of material around the young sun tend to be unable to recreate many features of the solar system as we observe it. For one thing, Earth appears to be made of two different types of rock, which wouldn’t make sense if they all came from the same ring. Additionally, single-ring models tend to end up with Mercury and Mars too large, Venus and Earth too close together, and the compositions of Earth and Mars too similar.
Bill Bottke of the Southwest Research Institute in Colorado and his colleagues constructed a series of detailed simulations of various ways in which planets could have formed from a single reservoir of material and subsequently evolved, but problems persisted.
“We spent six months in front of the computer, nothing worked, so we made a desperate play. We thought: why not try a second tank?” Bottke said while presenting this work at the Lunar and Planetary Science Conference in Texas on March 16. “It turned out that this model not only did a great job of creating the terrestrial planets, but it also did a really good job of explaining some things that were bothering us.”
The best-fit model had two separate disks, one about half the current distance between the Sun and Earth, and the other about 1.7 times the Sun-Earth distance. This simulation ended with all planets at the correct sizes and distances.
It also matches the compositions of Earth, Moon and Mars. “We believe that the Earth formed mainly from [inner solar system] “Earth is formed from the inner disk, with slight contributions from the outer disk, as Bottke’s model predicts, it would match these expectations. Mars, on the other hand, would form mainly from the outer disk, which explains the differences between the composition of the two planets.
There are concerns that the model requires very specific initial conditions to correctly reproduce the inner solar system, and it is not 100% clear why these conditions would have the required values. “Slight changes in disk shape can lead to major differences in the direction of terrestrial planets,” Bottke said.
The researchers are now working to refine their model and explore its further implications for the solar system. “We use a lot of time on our supercomputer to try every reasonable possibility,” Bottke said. If it works, this new explanation could explain all kinds of solar system mysteries, from strange asteroids to unexplained rocks on the lunar surface.
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