The spectrum of the quasi-moon Kamo`oalewa shows striking similarities to that of moon rocks taken during the Apollo missions. And that can only mean one thing…

Our Earth has multiple quasi-moons; natural objects that take as much time to complete a circle around the sun as our planet. With a diameter of 40 to 100 meters, Kamo’oalewa is the smallest, but also the closest and most stable quasi-moon known to Earth. In a new study, researchers took a closer look at this space rock. And that leads to an astonishing discovery.

Earth’s quasi-moons
In addition to Kamo’oalewa, Earth is also home to several other quasi-moons, including Cruithne; an asteroid about two kilometers in size that approaches Earth at a distance of 12 million kilometers. Most quasi-satellites accompany Earth only temporarily. However, temporary is a fairly broad term in this case. Even the quasi-satellite with the most unstable orbit has been traveling with Earth for nearly 1,000 years. And most quasi-satellites do that for much longer; sometimes thousands or even hundreds of thousands of years. Since most quasi-satellites have only been found quite recently, more are expected to be discovered.

Much about quasi-moons is still unknown. That’s because these objects are very faint and hard to see. For example, Kamo`oalewa is about four million times fainter than the faintest star visible to the human eye in the night sky. Kamo`oalewa was discovered in 2016 by NASA astronomers with the Pan-STARRS 1 telescope, located on the Hawaiian shield volcano Haleakala. The name is derived from a Hawaiian creation song.

Research

In a new study, researchers decided to take a closer look at the quasi-moon. Something that is not so easy, by the way. Because of its orbit, Kamo`oalewa can only be observed from Earth for a few weeks in April. In addition, due to its small appearance, the quasi-moon can only be viewed with one of the largest telescopes on Earth.

broken piece

Last April, the researchers held the gigantic Large Binocular Telescope – the largest telescope in the world – at the ready. And that leads to a special discovery. Using the telescope, the team found that Kamo`oalewa’s pattern of reflected light — or spectrum — is strikingly similar to that of moon rocks taken during the Apollo missions. And that suggests that Kamo`oalewa may be a broken-away piece of our own moon.

Lost

So it may well be that the fairly recently discovered quasi-moon may represent a lost fragment of our own natural satellite. Another indication of this is that Kamo`oalewa’s orbit is similar to Earth’s, but with a smaller inclination. In addition, its orbit is not typical of other asteroids orbiting Earth. “It is highly unlikely that a near-Earth asteroid will spontaneously enter a quasi-lunar orbit like Kamo’oalewa’s,” said researcher Renu Malhotra. And if it did, this object probably wouldn’t stay in this particular orbit for long. “Maybe 300 years,” Malhotra continues. “But we think Kamo’oalewa took this job about 500 years ago.”

The team is not yet sure how exactly Kamo`oalewa could have broken away from our moon. There are also no other known asteroids that may have descended from our moon. “I looked at every nearby asteroid, but nothing matched,” said study leader Ben Sharkey. The researchers are already working on a follow-up study to further study the origin of the quasi-moon, with the hope of unraveling the mystery in the near future.