The study of ancient asteroids reveals the tumultuous past of the solar system

According to a recent study of two Trojan asteroids of Jupiter, a reorganization of the outer planets of the solar system would have taken place at the beginning of its formation.

American astrophysicist David Nesvorny and his colleagues at the Southwest Research Institute have studied a rare pair of asteroids named Patroclus and Menoetius, located at about the same distance from the Sun as Jupiter, one in orbit in front of and the other behind the gas giant.

These asteroids will be at the center of NASA's Lucy mission which will be launched in 2021. According to the researchers, these are remnants of the primordial material that led to the formation of the outer planets (Saturn, Jupiter, Neptune Uranus). They would thus witness the birth of the solar system more than 4 billion years ago.

Patroclus and Menoetius have a width of about 113 km and revolve around the Sun. They are the only known binary system in the Trojan asteroid population of Jupiter. In astronomy, the term "Trojan Horse" is used to refer to a small object that shares a relationship with two other larger bodies.

Current work shows that the presence of Patroclus and Menoetius, as well as others in Jupiter's orbit, would be the result of an early planetary rearrangement in our system. The pair would have formed from the initial disk of material beyond Neptune.

The simulations suggest that the presence of the celestial couple today at this location indicates that the dynamic instability between the giant planets must have occurred during the first 100 million years of solar system formation. . These objects were probably captured during a dramatic period of dynamic instability during a collision between the giant planets of the solar system.

This great upheaval would have pushed Uranus and Neptune outward, where they would have met a large population of small bodies that would be the origin of the current objects of the Kuiper belt, which orbit the edge of the solar system.

According to the researchers, several small bodies of this primordial Kuiper belt were scattered inward and some of them became Trojan asteroids. Indeed, recent simulations of the formation of small bodies suggest that binary systems such as Patroclus-Menoetius are remnants of the very first moments of the birth of the system.

Current observations of the Kuiper belt show that these binary systems would have been common during the genesis of the system. There are only a few left in Neptune's orbit. The question is how did they survive until today, "says researcher William Bottke.

The dynamic model of the early instability of the solar system proposed in the current work also has important consequences for rocky planets, especially with regard to the origin of the large impact craters on the Moon, Mercury and Mars, which formed about 4 billion years ago.

According to this model, the meteorites that have dug these craters are less likely to reach the peripheral areas of the solar system. This could mean that they were made by remnants of small bodies from the process of forming rocky planets. The details of these works are published in the journal Nature Astronomy.