Composition and Space Weathering Characteristics of Tianwen-2 Mission's First Target Near-Earth Asteroid (469219) Kamo`oalewa

TL;DR

This study re-analyzes spectral data of asteroid Kamo`oalewa to infer its mineral composition and space weathering state, revealing higher olivine content and immature weathering, which informs future exploration strategies.

Contribution

It provides a detailed spectral analysis of Kamo`oalewa, estimating its mineralogy and weathering degree, advancing understanding of its surface properties for mission planning.

Findings

Higher olivine abundance than typical S-type asteroids

Exhibits immature to submature space weathering

Spectral similarity to certain asteroid taxonomies

Abstract

The near-Earth asteroid Kamo`oalewa, a quasi-satellite of the Earth and the target for sample return by China's Tianwen-2 mission, exhibits distinctive spectral characteristics. This study re-analyzes the visible and near-infrared reflectance spectrum of Kamo`oalewa published by B. N. L. Sharkey et al. (2021), obtained using the Large Binocular Telescope, to infer its mineral composition and space weathering characteristics. Spectral similarity analysis is performed by comparing the spectrum of Kamo`oalewa to the mean spectra of various types in the Bus-DeMeo taxonomy to make a preliminary constraint on the combined characteristics of surface mineralogy and space weathering effects. To further characterize the mineral composition, a detailed analysis of the 1 {\mu}m band center is conducted based on spectral data below 1.25 {\mu}m that have higher signal-to-noise ratios. Empirical models for normalized spectra are developed to estimate the Is/FeO content. The results suggest that asteroid Kamo`oalewa has higher olivine abundance than that of typical S-type asteroids and the Moon, exhibiting an immature to submature degree of space weathering. These findings enhance our understanding of the evolution of similar quasi-satellites and provide important implication for the future exploration of Tianwen-2 mission.