Tracing Giant Planet Migration with Chondrite Meteorites

The period of orbital instability that led to the migration of the Solar System's giant planets to their current orbit occurred between 60 and 100 million years after the beginning of Solar System formation, researchers report. The findings – based on an analysis of the relationship between lowiron enstatite (EL) chondrites and Athor family asteroids – not only provide new insight into the Solar System's evolution but may also shed light on the conditions that led to the formation of Earth's moon. The giant planets of the Solar System – Jupiter, Saturn, Uranus, and Neptune – formed closer to the Sun than they are now and migrated to their current wider configuration during a period of orbital instability. Although the timing of this orbital instability is poorly constrained, previous estimates have suggested that it had an upper limit of less than 100 million years (Myr) after the start of Solar System formation. To better understand when this migration occurred, Chrysa Avdellidou and colleagues examined the Athor family of asteroid fragments produced by an asteroid collision that destroyed a progenitor asteroid ~3 billion years ago. According to the authors, determining the scenario in which the material from this collision became implanted into the Solar System's asteroid main belt could be used to date the timing of the orbital instability that led to the giant planets' migration. Using thermochronometer models, orbital dynamics simulations, and meteorite data, Avdellidou et al. discovered a connection between EL chondrite meteorites and Athor family asteroids, which indicates that their implantation into the asteroid main belt occurred more than 60 Myr after the Solar System began to form, providing a lower limit for the Solar System's giant planet orbital instability. Moreover, the authors note that the giant impact that led to the formation of Earth's moon also occurred within this range (60-100 Mry) and speculate that the two events may be related.