A promising view to the Moon: Anticipations for Tianwen-2 samples returned from Kamo’oalewa

Explorations of asteroids have received increasing attention since the 1990s because of the unique information those objects contain about the history of the early solar system. Quasi-satellites are a population of asteroids that co-orbit closely with, but outside the gravitational control of, the planet. So far, only five Earth quasi-satellites have been recognized, among which (469219) Kamo’oalewa (2016 HO3) is currently considered as the most stable and the closest one. However, little is known about this particular asteroid or this class of near-Earth asteroids because of the difficulties in observing them. China has announced the Tianwen-2 asteroid sample return mission to Kamo’oalewa, to be launched in 2025. Here, we review the current knowledge of Kamo’oalewa in its physical characteristics, dynamic evolution, surface environment and origin, and propose the possible breakthroughs that the samples could bring us about the asteroid Kamo’oalewa as an Earth quasi-satellite. From its prevailing provenance as debris of the Moon, confirming the origin of Kamo’oalewa could be a promising start to infer the evolution history of the Moon, probably including a more comprehensive view of the lunar farside and the origin of asymmetry between two sides of the Moon. Comparing the samples from the Moon and Kamo’oalewa will also provide new insights to better understand the Earth wind.