A Collision Mechanism for the Removal of Earth's Trojan Asteroids

TL;DR

This study uses N-body simulations to investigate how large collisions on Earth could have disrupted or eliminated its primordial Trojan asteroids, explaining their current absence.

Contribution

It demonstrates that significant Earth collisions could have destroyed the primordial Trojan population, providing a possible explanation for the lack of Earth Trojans.

Findings

Large Earth collisions can disrupt Trojan populations.

Approximately 99% of primordial Trojans could be lost after such collisions.

Earth's Trojan absence may be due to past catastrophic impacts.

Abstract

Due to their strong resonances with their host planet, Trojan asteroids can remain in stable orbits for billions of years. As a result, they are powerful probes for constraining the dynamical and chemical history of the solar system. Although we have detected thousands of Jupiter Trojans and dozens of Neptune Trojans, there are currently no known long-term stable Earth Trojans. Dynamical simulations show that the parameter space for stable Earth Trojans in substantial, so their apparent absence poses a mystery. This work uses a large ensemble of N-body simulations to explore how the Trojan population dynamically responds if Earth suffers large collisions, such as those thought to have occurred to form the Moon and/or to have given Earth its Late Veneer. We show that such collisions can be highly disruptive to the primordial Trojan population, and could have eliminated it altogether. More specifically, if Earth acquired the final 1\% of its mass through ${\cal O}(10)$ collisions, then only $\sim1\%$ of the previously bound Trojan population would remain.