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Odd asteroid seems to be a broken piece of the Moon

By Michael Irving
November 11, 2021
Odd asteroid seems to be a broken piece of the Moon
An artist's impression of Kamo`oalewa, a small near-Earth asteroid that a new study suggests is a fragment of the Moon
An artist's impression of Kamo`oalewa, a small near-Earth asteroid that a new study suggests is a fragment of the Moon
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An artist's impression of Kamo`oalewa, a small near-Earth asteroid that a new study suggests is a fragment of the Moon
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An artist's impression of Kamo`oalewa, a small near-Earth asteroid that a new study suggests is a fragment of the Moon

A curious space rock has just gotten curiouser. The asteroid Kamo`oalewa has an odd orbit that makes it almost a mini-moon of Earth – and now it may really earn that title, as new observations show that it could in fact be a fragment of the Moon.

Discovered in 2016, Kamo`oalewa measures about 40 m (130 ft) wide and rotates once every 28 minutes or so. Technically it orbits the Sun, but it also kind of orbits Earth at a distance 13.6 times further than the Moon, alternating between swinging out ahead of us and lagging behind. That makes it a “quasi-satellite.”

Despite its relative proximity to Earth, Kamo`oalewa is tricky to study, being small, faint and only visible for a few weeks every April. So for the new work, astronomers peered through that window earlier this year to study the elusive rock using the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT).

The team measured the object’s spectrum, the pattern of light that reflects off its surface. Because different elements reflect and absorb different wavelengths of light, scientists can use an object’s spectrum to determine what it’s composed of. In this case, Kamo`oalewa was mostly silicate-based.

That fingerprint didn’t match any other known near-Earth asteroid, the team says. The closest match was to lunar rocks brought back by Apollo astronauts, suggesting Kamo`oalewa is a piece of the Moon that broke off at some point, perhaps during some kind of impact event. That would make it the first known asteroid of lunar origin, and its unusual orbit lends weight to that hypothesis.

"It is very unlikely that a garden-variety near-Earth asteroid would spontaneously move into a quasi-satellite orbit like Kamo`oalewa's," says Renu Malhotra, co-author of the study. "It will not remain in this particular orbit for very long, only about 300 years in the future, and we estimate that it arrived in this orbit about 500 years ago."

Further work by the team will focus on tracking down Kamo`oalewa’s origins in more detail.

The research was published in the journal Nature Communications Earth and Environment.

Source: University of Arizona

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SpaceAsteroidAstronomyEarthMoonUniversity of Arizona
8 comments
Michael Irving
Michael Irving
Michael has always been fascinated by space, technology, dinosaurs, and the weirder mysteries of the universe. With a Bachelor of Arts in Professional Writing and several years experience under his belt, he joined New Atlas as a staff writer in 2016.

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8 comments
vince
We have two moons! Who would have thought.
Expanded Viewpoint
Many years ago, I read an historical account of a man who was observing the moon back in the 1800's I think it was, and he described something striking the moon, and when it did, he said that it shot up a huge amount of "hot coals and ashes" that were quite bright and he was very impressed by it all. This would fall far inside of the estimate of 500 years ago being the time frame for the creation of this space rock though. Of course back then, no one really knew what our moon was composed of, so he had to apply what he was familiar with, which was burning organic material, like in a cooking fire.
This space rock could have come from an impact on the dark side of the moon, and if it happened during our day light hours, on a cold and cloudy winter's day, no one would have seen any flash of light or plume of ejecta.
Username
@Expanded - there is no constant "dark" side of the moon. There is a perpetual "far" side of the moon.
DJ's "Feed Me Doggie"
It shold have been named "Butt-Head", since we now have two moons.
Expanded Viewpoint
Since our moon does not rotate on an axis, we see only one half of it, and because we do not see the other side of it, it can be said to be "dark" to us. But yes, you are right, the sun does shine on the far side, we just don't see it from here. Due to Earth being on one side of it, the far side is much more exposed to cosmic debris and is quite jagged with many large craters from meteor impacts.
A.L.
The most likely scenario is that the asteroid was blasted out of the Moon’s surface by an impact event, perhaps the one that carved the immense Mare Orientalis into the Far Side, the largest impact crater on the Moon by a wide margin.

As for

“Kamo`oalewa measures about 40 m (130 ft) wide and rotates once every 28 minutes or so. Technically it orbits the Sun, but it also kind of orbits Earth at a distance 13.6 times further than the Moon…”

That’s 13.6 times FARTHER (literal distance) than the Moon, not further (metaphorical distance).
Kevin Ritchey
The article states that it only has about 300 years left in its current orbit but says nothing about after that. Leaves one wondering…
Unsold
I'm wondering if it's just an gravitational aglomeration of impact debris or something more solid, like metals.