Earth’s ‘quasi-moon’ probably rocketed away from the actual moon relatively recently in the solar system’s history, a new study suggests.
Kamo’oalewa, a 131- to 328-foot-wide (40 to 100 meters) Near Earth Object (NEO), was liberated between 1 million and 10 million years ago by an asteroid impact, an impact that destroyed the 13.7-mile-wide ( 22 kilometers) Giordano Bruno crater, the research shows.
Kamo’oalewa, or “469219 Kamo’oalewa” as it is officially called, was discovered in 2016 by the Pan-STARRS 1 asteroid survey telescope on Haleakalā, Hawaii, as part of NASA’s planetary defense effort to discover space rocks that may be our planet could hit. .
Kamo’oalewa, which means “an oscillating celestial body” in Hawaiian, was later found to orbit the Sun in synchrony with Earth and spins extremely fast for an asteroid. These puzzling features led scientists to investigate the origins of the quasi-moon. In 2021, research found that Kamo’oalewa’s composition is similar to rocks recovered from the moon, hinting at the moon’s origins. The question was: where exactly on the moon did it come from?
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“Our main findings are that Kamo’oaelewa originates from the moon, and not from the asteroid belt, unlike the majority of asteroids belonging to the NEO population,” said Patrick Michel, team member and senior researcher at Center National de la Recherche Scientifique. CNRS), the French state research agency, told Space.com.
“Like detectives, we used all known information about this Kamo’oalewa and the lunar surface to deduce a scenario for the origin of this object, starting from the impact that created the Giordano Bruno crater,” Michel said.
Recreating a ‘cosmic crime scene’ on the moon
The team connected Kamo’oalewa to the Giordano Bruno Crater by working as crime scene investigators. They used a computer model to simulate the type of impact that a space rock like this quasi-moon would have caused.
That meant taking into account things like the size and velocity distribution of the resulting ejecta and their dynamic evolution. This reconstruction showed that some ejecta would eventually come into 1:1 orbital resonance with Earth, with the same dynamical properties as Kamo’oalewa.
“Our results tell us that Kamo’oalewa is very likely a fragment of the lunar surface for which we have a direct relationship with a known crater if our scenario is correct,” Michel said.
“Usually the best we can do is determine the source region in the asteroid belt of a NEO, knowing its current orbit. A region is usually very broad in these types of estimates, such as the inner or outer asteroid belt,” he says. added. “Here we have identified a very specific body and location where this object came from, which is very exciting.”
Michel explained that Kamo’oalewa’s orbit is not stable, leading the team to link it to a crater that is not too old, possibly between one and ten million years old.
“Then we also needed to ensure that the crater was not too large so that an intact fragment the size of Kamo’oaelewa could be produced,” he continued. “The best candidate at the time was Giordano Bruno, who meets both restrictions.”
The team’s impact modeling also gave them an idea of the size of the space projectile that would have created the nearly 14-mile-wide lunar crater and its quasi-lunar ejection. They estimate that the asteroid that struck the moon would have had to have been about 1 mile (1.6 kilometers) wide to carve out the Giordano Bruno crater and free Kamo’oalewa.
If an asteroid of that size were to hit Earth, it would release about the same amount of energy as the explosion of a one million megaton bomb.
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The findings also have implications for our understanding of the NEO population around Earth, implying that a larger proportion of these bodies than suspected could have been created by impacts on the moon or on other bodies in the solar system.
“While the majority of NEOs come from the main asteroid belt between Mars and Jupiter, a small portion may come from the moon or other locations,” Michel said. “If there is something unusual and a lunar origin seems possible, we now know that we can check whether a fragment of the moon can lead to the orbit of the object under consideration and possibly identify the crater from which it came, thus the loop is closed.” .”
Michel added that the discovery that Giordano Bruno Crater and NEO Kamo’oalewa are likely linked is a stark reminder that even in this later, quieter era of the solar system’s 4.6 billion year history, impacts through massive space rocks.
This highlights the importance of planetary defense projects such as NASA’s recent Double Asteroid Redirection Test (DART), which studied the effectiveness of redirecting an asteroid on a collision course with Earth.
“Impacts occur in the inner Solar System, but while traces are erased on Earth, they are not erased on the Moon. Our natural satellite thus contains the record of impact history in the Earth’s environment over the past 4 billion years” , Michel said. . “This is why some of us are deeply involved in planetary defense, the NASA DART mission that performed the first asteroid deflection test and the European Space Agency’s Hera mission, for which I serve as principal investigator, which measured the impact of the DART will measure in detail.”
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Michel admits that the team’s results are only preliminary. So while they have shown a strong link between Kamo’oalewa and the moon, further research on the asteroid will be needed to confirm this link.
“The next most exciting study of Kamo’oalewa will be offered by China’s Tiawen-2 mission which should launch in 2025 to sample the asteroid’s surface and return the samples to Earth for laboratory analysis,” he said . “This is a very challenging mission because no one has ever visited such a small object that orbits itself in just 28 minutes.
“The analysis of samples will tell us for the first time what [are] the physical and thermodynamic state of a fragment of this size extracted from the lunar surface by an impact, something we cannot determine in our impact model.”
The team’s research was published Friday (April 19) in the journal Nature Astronomy.