An asteroid the size of a Disney castle may be part of Earth’s Moon: study

Does the Earth have a second moon? Some might suggest it. The asteroid known as Kamoʻoalewa is the most stable quasi-satellite on the planet in terms of its orbit, but while it likely doesn’t qualify as a moon, it may in fact be a piece of us, a new study suggests.

Discovered in 2016 by scientists at the University of Hawaii, the asteroid, also designated 469219 (2016 HO3), takes its name from the Hawaiian language and is a combination of words that mean “the”, “fragment”, “of” and “to range.”

The asteroid itself is only around 46 to 58 meters in diameter, comparable in size to the Leaning Tower of Pisa in Italy or Cinderella’s Castle at Disney World. As such, while its proximity to the planet has led to it being labeled a Near Earth Object (NEO), it is not considered a Potentially Hazardous Asteroid (PHA), which is at least 140 meters in size.

But what is especially interesting is its orbit and its relationship to Earth.

Kamoʻoalewa is designated as an Apollo-class asteroid, which means that its orbit around the Sun frequently places it close to Earth. However, the Earth’s orbit also has an effect on the asteroid. Essentially, it circles the Sun closer than Earth, but often crosses outside of Earth’s orbit. It is further influenced by the planet’s gravity as it rotates around Earth’s orbital plane in what the manager of NASA’s NEO Study Center at the Jet Propulsion Laboratory, Paul Chodas, described as a jumping game of frog. This is a process that has been going on for almost a century and is expected to last for centuries to come.

It is for this reason that it is known as Earth’s “constant companion” and is considered the best example of a quasi-satellite.

“The loops of the asteroid around the Earth shift a little bit forward or backward from year to year, but when they shift too far forward or backward, Earth’s gravity is strong enough to reverse the drift and hold on to the asteroid so that it never travels more than about 100 times the distance from the moon ” Chodas said in 2016. “The same effect also prevents the asteroid from getting much closer than about 38 times the distance from the moon. In effect, this little asteroid is caught in a little dance with Earth.”

Earth has one true satellite, the Moon, and it is said to have five known quasi-satellites. Of these, Kamoʻoalewa is by far the most stable. But it appears to be very different from other asteroids.

The recent study, published in the academic journal Communications Earth and environment, started in 2016 and examined the asteroid using the Large Binocular Telescope and Lowell Discovery Telescope to take a full look, and found that the asteroid is reddened, in reference to its particular pattern of reflected light, also known as a spectrum. That in itself may not be too out of the ordinary, but the amount of redness is far greater than what has been seen in other asteroids in the inner solar system.

What could this mean?

There is another object in the inner solar system that has the best spectral match: the Moon.

Moon. (credit: Wikimedia Commons)

By analyzing lunar samples taken from the Apollo 14 mission, the researchers found it to be the closest match. Essentially, this means that Kamoʻoalewa must have broken off the lunar surface at some point.

But this has another problem, since although it is possible, it is also unprecedented.

“I looked through all the near-Earth asteroid spectra that we had access to, and nothing matched,” said lead study author Ben Sharkey, a graduate student at the University of Arizona, in a statement. statement, regarding that there are no other known NEOs that are believed to have detached from the Moon.

Unsure at first and struggling for three years, the researchers had to make another observation of the asteroid. However, COVID-19 turned off the telescopes needed to view it in April 2020, costing them a chance to take another look. This was difficult, as Kamoʻoalewa is extremely faint, 4 million times fainter than the faintest visible star in the sky. Seeing it without a telescope is impossible.

But in the spring of 2021, they were finally able to observe Kamoʻoalewa and the pieces began to come together.

Observations supported the idea that it fell off the Moon, and there is more evidence to support this. According to Renu Malhotra of the University of Arizona, who led the orbit analysis portion of the study, another clue is the orbit.

Kamoʻoalewa’s orbit is not typical of other NEOs, and it is very similar to Earth’s, only slightly inclined.

“It is highly unlikely that a garden-type near-Earth asteroid will spontaneously move into a quasi-satellite orbit like Kamoʻoalewa,” he explained. “It will not stay in this particular orbit for long, only about 300 years in the future, and we estimate that it reached this orbit about 500 years ago.”

How it separated from the Moon remains a mystery, and Malhotra’s lab is currently working to investigate it further.

But they are not the only ones interested in this asteroid.

Currently, Kamoʻoalewa is anticipated to be one of the targets of China’s planned ZhengHe mission. Scheduled to launch in 2024-2025, this robotic problem will target Kamoʻoalewa and Comet 311P / PanSTARRS to collect samples.

When these samples finally return, the nature of the asteroid may become clearer.

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