The Earth’s quasi-satellite Kamu-Arewa may have been a piece of lunar debris. Its origins are revealed through simulations WIRED.jp

You might think that astronomers have already discovered all the near-Earth asteroids and comets. However, this is not actually the case. Some of them are hidden in orbit in places that are difficult to monitor. This is because it is located in a location that can only be discovered by looking directly at the sun.

One such object is asteroid 469219 Kamoʻoalewa. It remained undiscovered until seven years ago, and even after its discovery, its origins remained shrouded in mystery. However, its origins have finally become clear.

Astronomers first discovered Kamoo’Alewa through a telescope above Haleakala volcano on the Hawaiian island of Maui. He gave it a Hawaiian name meaning “vibrating heavenly body.”

This celestial body is considered a “semi-satellite” of the Earth. Although its presence is small, from Earth’s perspective it appears to be a constant nearby companion, just like the distant Moon. However, it actually flies outside the influence of Earth’s gravity and orbits around the Sun instead of the Earth.

Astronomer Renu Malhotra of the University of Arizona thought early on that the object might be different from the asteroid belt, where most near-Earth objects originate. “We realized that its orbital characteristics made it different from other near-Earth asteroids, and that it might have a different origin,” Malhotra says.

When her team measured the spectrum of light, it looked suspiciously similar to silicates found on the Moon, not on asteroids. The result isPublished in 2021.

So the research team came up with a dramatic theory. The 50-metre-long space rock was blown off the moon by an asteroid impact millions of years ago.

They found that Duck-o-Arewa’s oscillating orbit actually agrees with this theory. The research team will share their research results with…Announced in late October.

What the simulation results revealed

Malhotra and doctoral student José Daniel Castro Cisneros used a digital model to simulate how a piece of moon rock would collide in space. It is possible for an asteroid to collide with the moon’s surface and drop pieces of regolith quickly enough to reach escape velocity, which means it will no longer fall to the moon’s surface, and the two have proven this with a model.

They then modeled the subsequent trajectories of these rocks and assessed whether any of them would end up in an orbit similar to that of Kamwarewa. It turns out that some of them actually do.

Such studies would require modeling a wide range of potential paths for impact-generated lunar debris. Malhotra and Castro-Cisneros found that a Kamwarewa-like path is rare but not impossible, occurring in 0.8% of the scenarios they studied.

This may seem unlikely, but it is more likely than competing theories that an asteroid coming from the asteroid belt was captured by gravity and ended up in such an unstable orbit. According to Castro Cisneros, the probability of a theory emerging in the asteroid belt is essentially zero.