The asteroid Kamo`oalewa flies just 14.4 million kilometers from Earth every April and may be a remnant from an ancient collision of the Moon.
A small asteroid orbiting close to Earth could be a fragment of the Moon, resulting from a long-ago collision, according to new research published on November 11 in the journal Nature Communications Earth & Environment. If confirmed, this asteroid will become the first near-Earth object originating from the Moon, potentially shedding light on the chaotic history of Earth and its natural satellite.
Simulation of the Kamo`oalewa asteroid flying near the Moon and Earth. (Photo: Addy Graham/University of Arizona)
The asteroid in the study is named Kamo`oalewa, which was discovered by astronomers in 2016 using the PanSTARRS telescope in Hawaii. Although the object is over 4 million times dimmer than what the human eye can see, every April, Kamo`oalewa’s orbit brings it close enough to Earth to be observed with the most powerful telescopes. During this time, the distance between the asteroid and Earth is 14.4 million kilometers, nearly 40 times the distance between Earth and the Moon.
Observations revealed that the asteroid has a diameter no larger than 58 meters, equivalent to a large bus. Due to its near-Earth orbit, Kamo`oalewa falls into a category known as quasi-satellite, meaning it orbits the Sun while remaining very close to our planet. Astronomers have previously discovered many quasi-satellites, but they faced challenges in conducting detailed studies due to their small size and dimness.
The origin of such objects is difficult to determine, but a team led by Renu Malhotra, a professor of planetary science at the University of Arizona, sought to explore the origins of Kamo`oalewa by studying the reflectance of light from its surface. Using the Large Binocular Telescope atop southern Arizona, the research team observed Kamo`oalewa as it approached Earth in April over several years.
They found that the light spectrum of the asteroid matched samples of lunar material collected from NASA’s Apollo missions, indicating that this object could indeed be a fragment of the Moon. Moreover, the asteroid’s extremely close orbit to Earth is very different from that of meteoroids coming towards our planet from the outer solar system. This suggests that Kamo`oalewa has been near Earth for a long time.
If Kamo`oalewa is a piece of the Moon, researchers have yet to determine what caused it to break off or how it came to be in its current orbit. However, after analyzing the object’s trajectory, the research team found three other near-Earth asteroids with similar orbits. All of them could have been ejected into space during the same collision with the ancient Moon. According to the research team, Kamo`oalewa will continue to orbit in its current path for another 300 years, providing them with ample opportunities to further investigate its origins.
