Asteroid Kamo`oalewa's journey from the lunar Giordano Bruno crater to Earth 1:1 resonance

TL;DR

This paper proposes that asteroid Kamo`oalewa originated from a recent lunar impact crater, supported by simulations linking its orbit and composition to a lunar fragment ejected from the Giordano Bruno crater.

Contribution

It introduces a novel hypothesis connecting Kamo`oalewa to a specific lunar crater, supported by numerical simulations and compositional analysis.

Findings

Kamo`oalewa's properties are consistent with a lunar origin.

Simulations suggest ejection from the Giordano Bruno crater.

Future missions can test the lunar origin hypothesis.

Abstract

Among the nearly 30,000 known near-Earth asteroids (NEAs), only tens of them possess Earth co-orbital characteristics with semi-major axes $\sim$1 au. In particular, 469219 Kamo`oalewa (2016 HO3), upcoming target of China's Tianwen-2 asteroid sampling mission, exhibits a meta-stable 1:1 mean-motion resonance with Earth. Intriguingly, recent ground-based observations show that Kamo`oalewa has spectroscopic characteristics similar to space-weathered lunar silicates, hinting at a lunar origin instead of an asteroidal one like the vast majority of NEAs. Here we use numerical simulations to demonstrate that Kamo`oalewa's physical and orbital properties are compatible with a fragment from a crater larger than 10--20 km formed on the Moon in the last few million years. The impact could have ejected sufficiently large fragments into heliocentric orbits, some of which could be transferred to Earth 1:1 resonance and persist today. This leads us to suggest the young lunar crater Giordano Bruno (22 km diameter, 1--10 Ma age) as the most likely source, linking a specific asteroid in space to its source crater on the Moon. The hypothesis will be tested by the Tianwen-2 mission when it returns a sample of Kamo`oalewa. And the upcoming NEO Surveyor mission will possibly help us to identify such a lunar-derived NEA population.