How the Solar System formed is a genuinely baffling mystery. Scientists gather all kinds of clues from all over the place, such as the positions and sizes of the planets, the objects existing in the asteroid belt, the number of moons located around the planets, and so on.
However, how did we get all the way to this from a dim disk of gas and dust that existed billions of years ago? Computer simulations and models are shedding some light into the process, and recently scientists have considered the asteroid belt for some more clues.
The reason is that the asteroids located at a close distance to the Sun actually keep traces from when the Solar System was still developing and might provide researchers with clues to the theory that we once had five massive planets.
The Young Solar System
According to scientists, our Solar System was billions of years ago, just a hand of random gas and dust drifting around as a nebula. After it crashed, it shaped a rapidly rotating carousel of a flat disk around the proto-Sun. During 100 million years, that disk somehow became the planets and other cosmic bodies found in our Solar System.
Computer simulations of the process are incredibly challenging to create because of all the intricate physics required, but they have a couple of general features. The interior worlds are prone to be small and rocky, while the outermost planets are usually giant and full of gas or ice. Moreover, the process of formation correlates to a cluster of random debris floating around.
Another feature is that young planets tend to travel more rapidly into loud motion, which means that rotations become integer multiples of each other. When it comes to our Solar System, in simulations, the massive planets are prone to form at a much closer distance to each other and much closer to the Sun than they are currently.
Traveling Far Away
In the original version of the Nice Model, named after the city in southern France, the close massive planets are enclosed by a disk of debris; more precisely, small planetesimals that never grow and remain at the edge of the Solar System.
However, even incredibly slowly, during 100 million years, the outermost massive planet moves closer to those leftovers – sufficiently close to engage gravitationally, performing an orbital movement where the planet drags the bit of rock inward to a smaller circuit, and in turn, propels itself farther out.
This particular model can explain overall the current positions of the planets, and the way they could get there from the place they took form.
The Asteroid Belt to Solve The Mystery
All versions of the Nice Model, however, have a specific issue with the asteroid belt. That movement towards the outer part of the system can have a considerable effect in the inner worlds.
Recently, a team of scientists thought of a more sophisticated approach to the simulations, observing the interplays of Jupiter and Saturn as they danced together while the Solar System was still young.
The experts discovered that during the process of planetary migration, both planets get closer to a 5:2 resonance, which means that Jupiter rotates five times for every Saturn orbits.
The more unusual models, like the ones of the early Solar System hosting a fifth massive planet, also depicted an impact on all the resonances. This means that the current asteroid belt may actually be a fossil record, keeping all the clues about what the early Solar System was like.