(ORDO NEWS) — Simulations of the formation of the solar system have been largely successful. It is able to reproduce the positions of all major planets along with their orbital parameters.
But with current simulations, it is extremely difficult to correctly determine the masses of the four terrestrial planets, especially Mercury.
A new study suggests we need to pay more attention to giant planets in order to understand the evolution of smaller planets.
Of all the rocky planets in the inner solar system, Mercury is the strangest. Mercury not only has the smallest mass, but also has a very large core relative to its size.
This poses a major problem for modeling planet formation, because it is difficult to build such a large core without growing a large planet along with it.
A team of astronomers recently explored several possible explanations for Mercury’s strange properties by running simulations of the formation of the solar system.
In the early days of the solar system, instead of a neat row of planets, we had a protoplanetary disk of gas and dust. Embedded in this disc were dozens of planetesimals that eventually collided, merged, and formed into planets.
Astronomers believe that the inner edge of the protoplanetary disk was probably relatively short of material. In addition, in that young system, the giant planets did not appear in their modern orbits.
Instead, they migrated from where they originally formed to their current positions. As these giant planets moved, they destabilized the inner disk, potentially removing even more material.
By combining these ideas, astronomers have been able to construct a history of Mercury’s formation.
Initially, the inner protoplanetary disk contained many planetesimals, but as the giant planets moved and migrated, they took with them a lot of the material from which the planets were built.
The remaining planetesimals collided with each other, and as a result of these collisions, a large amount of heavy metals was thrown into the innermost planet, creating the large core of Mercury.
The models reflected the size of Mercury’s core, but failed to correctly determine the planet’s total mass. The simulations usually resulted in a Mercury that was two to four times as massive as it actually is.
It remains an open question how Mercury appeared. Astronomers suspect that we need to take a closer look at the chemical properties of the protoplanetary disk.
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