There are a small number of objects that scientists call quasi-satellites that orbit Earth. One of them is called Kamo'oalewa , and it is a near- Earth asteroid . It resembles the Moon in some aspects and could be a part of it.
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The asteroid was discovered in 2016 with Pan-STARRS at Haleakala. It is an unusual object because its orbit changes over time. But as it changes, it always stays close to Earth.
Its surface is also remarkable. It reflects light in the same way that the Moon does, thanks to the presence of silicates. This is an interesting clue to its origin, but it is not the only one. While Kamo'oalewa is not the only quasi- satellite, it is nevertheless the smallest, the closest, and the most stable of them.
A new study examines the object's orbit to understand whether it could have originated from the Moon. The study is called Orbital pathways for a Lunar-Ejecta Origin of the Near-Earth Asteroid Kamo`oalewa. The lead author is Jose Daniel Castro-Cisneros of the Department of Physics at the University of Arizona.
Sometimes, small bodies in the Solar System do not follow heliocentric orbits. Instead, due to orbital resonances, they can share the orbit of a planet. These are called co-orbital objects.
Kamo'oalewa lies beyond Earth's Hill sphere, which is a region of space that dominates the pull of satellites. The Moon lies within the Hill sphere, and although its orbit is subject to minor perturbations and changes, it is fairly stable. But Kamo'oalewa lies outside the sphere, and its orbit is highly elliptical. It is called a quasi-satellite because the Sun exerts a greater pull on it than the Earth.
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Since they can't go back in time and watch the Moon's history, scientists do the next best thing. They use computers to simulate events with a wide variety of variable values and see what they find. In this paper, the researchers modeled particles ejected from the Moon by collisions.
Most of the particles in their simulation leave the neighborhood of Earth and the Moon and transition into orbits around the Sun, which is not surprising. The dominant mass of the Sun influences everything in the Solar System.
But some do not enter heliocentric orbits. Instead, they occupy orbits similar to that of Kamo’oalewa.
Kamo’oalewa has a moderate eclipsing inclination of about 8°. In the simulation, most launched particles have inclinations even smaller than that, usually between 1° and 3°. But some of them reached higher inclinations similar to Kamo’oalewa.
Simulations show that Kamo'oalewa does not need to have started journey with its highest inclination compared to other particles. Its inclination also does not stay at 8°. During close approaches to Earth, it experiences jumps in inclination that occur over hundreds of years and then change again.
If scientists can prove that Kamo'oalewa is a piece of the Moon, then that would open up some interesting possibilities. It would be a first and "... would be of great interest for cosmochemical study as a sample of ancient lunar material," the authors write.
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There is talk of missions to Kamo'oalewa, but it may not be very intense. If all or some of these missions are successful, we will finally be able to determine whether Kamo'oalewa is indeed a part of the Moon.
