Tianwen-2 target asteroid (469219) Kamo'oalewa probably develops an Itokawa-compositional but ultra-highly space-weathered surface

TL;DR

The paper suggests that asteroid Kamo'oalewa has an Itokawa-like composition with an ultra-highly space-weathered surface, likely originating from the Flora family, based on spectral analysis and space weathering experiments.

Contribution

It introduces a new scenario for Kamo'oalewa's composition and origin, supported by spectral reanalysis and space weathering experiments on meteorites.

Findings

Kamo'oalewa's spectrum matches highly space-weathered LL chondrites.

Kamo'oalewa likely originated from the Flora family via the v6 secular resonance.

Kamo'oalewa has an Itokawa-like composition with a highly space-weathered surface.

Abstract

China's Tianwen-2 mission plans to return samples from a small, rapidly spinning Earth quasi-satellite (469219) Kamo'oalewa. Previous studies linked Kamo'oalewa to lunar composition and origin. Here, we propose another scenario. We reanalyzed the reflectance spectrum of Kamo'oalewa and obtained an absorption band center at 1.001+-0.028 um (error is 1sigma), consistent with LL chondrites. We then conducted space weathering (SW) experiments on meteorites and found that highly space-weathered LL chondrite powder (but not slab) successfully reproduced the reflectance spectrum of Kamo'oalewa. We further traced the dynamical origin of Kamo'oalewa and found that it probably originated from the v6 secular resonance, and more specifically, the Flora family. Kamo'oalewa exhibits a similar composition to Itokawa and 7 objects in the Flora family, but with a higher degree of space weathering. We, therefore, proposed that Kamo'oalewa probably originated from the Flora family and developed an Itokawa-compositional, highly space-weathered, fine-regolith-dominated surface.