A mysterious near-Earth asteroid the size of a Ferris wheel could actually be an ancient fragment of our Moon , according to a new study published by researchers at the University of Arizona (USA) in the journal Communications Earth & Environment. . The object belongs to a handful of known quasi-satellites, a subcategory of near-Earth asteroids that orbit the Sun but remain relatively close to Earth. In essence, they often appear to orbit the Earth, like the Moon, but actually remain gravitationally attached to the Sun rather than the Earth.
A ‘son’ of the Moon
The origins of these quasi-satellites are mysterious. 469219 Kamo`oalewa , for example, is interesting in that it never moves more than 100 times the distance to the Moon from us , and this new research reveals that it was probably once part of the Moon, presumably after being destroyed by an asteroid collision.
Kamo`oalewa was discovered using the PanSTARRS telescope in Hawaii. It is difficult to study because it does not reach 60 meters wide. Its orbit only makes it visible for a part of each month of April, and then it is only “available” for very large telescopes, as it is about 4 million times fainter than the dimmest star that the human eye can capture in a dark sky. .
“Its orbit is also not typical for near-Earth asteroids ,” said Renu Malhotra, a planetary scientist at the Lunar and Planetary Laboratory at the University of Arizona, Tucson. “It is highly unlikely that a near-Earth asteroid will spontaneously move into a quasi-satellite orbit like Kamo’oalewa’s. It will not stay in this particular orbit for very long, only about 300 years in the future, and we estimate that it reached this orbit about 500 years ago. “
In this most recent effort to learn more, the researchers made use of one of the most powerful telescopes on Earth, the Large Binocular Telescope run by the University of Arizona on Mount Graham in southern Arizona. In 2017, they obtained observations that included the spectrum of the asteroid, the distinctive pattern generated by the way Kamoʻoalewa reflects light from the Sun. Initial results showed that Kamoʻoalewa has a spectrum very similar to that generated by lunar rocks returned by the Apollo missions. , that is, it reflects sunlight like minerals found on the Moon, so it could be a fragment detached from our satellite. After missing the opportunity to observe it in April 2020 due to COVID-19 lockdown, the team found the final piece of the puzzle in 2021.
“It is easier to explain with the moon than with other ideas,” said Ben Sharkey, a co-author of the work.
In fact, its orbit offers us a fairly obvious clue to its lunar origins. Its orbit is similar to that of the Earth, but with minimal inclination.
Only five quasi-satellites have been confirmed , but their discoveries are so recent (the first was found in 2004) that there are probably many more waiting to be discovered.
Referencia: “Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa” 11 November 2021, Communications Earth & Environment.
DOI: 10.1038/s43247-021-00303-7
