How Ancient Collisions Explain Current Planetary Orbits

The migration of Jupiter, Saturn, Uranus, and Neptune from closer to wider orbits around the sun occurred 60-100 million years after the Solar System’s formation, possibly influencing the formation of Earth’s moon.

The migration of the Solar System’s giant planets—Jupiter, Saturn, Uranus, and Neptune—to their current orbits occurred between 60 and 100 million years after the formation of the Solar System, according to new research. These findings, derived from an analysis of low-iron enstatite (EL) chondrites and the Athor family of asteroids, offer fresh insights into the evolution of our Solar System. They may also shed light on the conditions that led to the formation of Earth’s moon.

Initially, the giant planets formed closer to the Sun and later migrated to their present, more distant positions during a period of orbital instability. While the exact timing of this instability has been difficult to determine, earlier estimates suggested an upper limit of less than 100 million years after the Solar System’s formation. To refine this timeline, Chrysa Avdellidou and her team studied asteroid fragments from the Athor family, which were created by the catastrophic destruction of a progenitor asteroid approximately 3 billion years ago.

The researchers proposed that the implantation of material from this collision into the Solar System’s main asteroid belt could help date the period of orbital instability. Using thermochronometer models, orbital dynamics simulations, and meteorite data, the team identified a link between EL chondrite meteorites and Athor family asteroids. This connection suggests that the material was implanted into the asteroid belt more than 60 million years after the Solar System began forming, setting a lower limit for the timing of the giant planets’ migration.

Furthermore, the study highlights a potential connection between this period of orbital instability and the giant impact that created Earth’s moon. The researchers speculate that both events occurred within the same timeframe, between 60 and 100 million years after the Solar System’s formation, indicating they may be interconnected.

For more on this study, see Tracing Planetary Shifts That Formed the Moon.

Reference: “Dating the Solar System’s giant planet orbital instability using enstatite meteorites” by Chrysa Avdellidou, Marco Delbo’, David Nesvorný, Kevin J. Walsh and Alessandro Morbidelli, 16 April 2024, Science.
DOI: 10.1126/science.adg8092

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