Of the 34 thousand known near-Earth asteroids, only a few dozen fly in an orbit close to the Earth’s. The trajectories of the rest only intersect the vicinity of the Earth’s orbit. Most of those “flying” in orbit near our planet are objects from the Asteroid Belt, located between the orbits of Mars and Jupiter. These are mainly carbon (class C) and silicon (class S) asteroids. Asteroid Kamoalev is not at all like them.
This asteroid was discovered in 2016. It flies in orbit around the Sun, but in the same “rhythm” as the Earth (in a 1:1 resonance). And close to the planet. Therefore, although Kamoaleva does not orbit the Earth, due to its trajectory it looks like a satellite – a quasi-satellite.
Particular interest in it arose in 2021. Data collected by the LBT observatory showed that Kamoaleva’s composition is more similar to the Moon than to a typical asteroid. To test the theory of lunar origin, an international team of astronomers resorted to computer modeling. The results were published in the journal Nature Astronomy.
The goal was to find the parameters of an asteroid collision with the lunar surface that could produce debris the size of Kamoalev. In addition, this fragment had to escape from the gravity of the Moon. It turned out that to form such a high-speed fragment with a diameter of 36-60 meters, an asteroid with a diameter of 0.78-1.44 kilometers is required. The impact event should have left a crater with a diameter of 10-20 kilometers.
It is noteworthy that the average rotation speed of the ejected fragments turned out to be close to the anomalously high rotation speed of Kamoalev. However, such rotation can be explained in another way. For example, the NORP effect and collisions with other asteroids.
There are tens of thousands of craters on the Moon with a diameter of over 10 kilometers, but most of them are billions of years old. Quasi-satellites are not survivable. Their lifespan is approximately 10 million years, in unique cases – about 100 million years. They either fly away, collide with each other and are destroyed, or fall to the Earth, Moon or Sun. This means that Kamoaleva is quite “young”. But there are only a few dozen “young” craters of suitable diameter on the Moon.
The youngest suitable lunar crater is Giordano Bruno, which is 22 kilometers in diameter and 1-10 million years old. The composition of Kamoaleva is similar to matter from the crater. Moreover, the asteroid’s material resembles samples collected by the Soviet Luna 24 mission, which are believed to have included material from the crater.
The scientists ran the model using Giordano Bruno’s parameters. It was formed by the fall of a body with a diameter of 1.66 kilometers. In this case, 100-400 fragments with a diameter of more than 36 meters should have formed. Of these, as the model showed, over the next 10 years only 40% to 18% “survive” (the further you go, the fewer “survivors”). It turns out that 50-120 of the 300 primary fragments of the Giordano Bruno crater can fly near the Earth.
Kamoaleva is still very “lucky”, because of all the debris, only a fraction of a percent enters an orbit similar to the orbit of this astroid. At best, if the collision occurred only a million years ago, Kamoalev may have two “brothers.”
It is not surprising that all this debris has not yet been discovered. According to researchers, to date only 1% of near-Earth asteroids of this size have been caught.
All this makes the upcoming Chinese Tianwen-2 mission, scheduled to launch in 2025, even more attractive. The device will go just to Kamoaleva, collect its samples and return to Earth with them. Given that the asteroid can withstand rapid rotation, it is likely that it is a monolithic object and not a “pile” of gravel like asteroids Bennu and Itokawa. Humanity has never explored such monolithic asteroids before.
