\”Mini Moon\” comes to earth to \”visit\”

Li Mingtao

Recently, a new friend has been added around the earth. An asteroid code-named 2024 PT5 was briefly captured by Earth\’s gravity and became Earth\’s \”mini-moon\” from September 29 to November 25, after which it will return to orbit around the sun again. The \”mini moon\” was discovered by observation instruments deployed in South Africa. It has an equivalent diameter of about 11 meters, which is equivalent to the height of three or four stories. Due to its small size and distance, the \”mini-moon\” is extremely dim and cannot be directly seen by humans with the naked eye.

It is not uncommon for asteroids to be captured by Earth\’s gravity. There are countless asteroids in the solar system. They are the remaining debris left after the formation of the solar system. There are tens of millions of asteroids orbiting the earth alone. They orbit the sun like the earth. When these asteroids intersect with the Earth\’s orbit, if their orbital energy is similar to that of the Earth, they may be captured by the Earth\’s gravity and become the Earth\’s \”mini moon.\” According to scientists\’ inference, there may be a \”mini-moon\” orbiting around the earth at any time, but currently human observation capabilities are limited and cannot locate its specific location.

Prior to this, humans have discovered four \”mini-moons\” that were briefly captured by the Earth\’s gravity, namely asteroids code-named 2006 RH120, 2020 CD3, 2022 NX1 and 1991 VG. Among them, the first two \”mini moons\” are only the size of a refrigerator or a car. They have circled the earth several times and are called \”temporarily captured earth orbiting objects.\” The latter two and the newly discovered 2024 PT5 asteroid only orbited millions of kilometers away from the earth for a few dozen days and did not actually fly around the earth. They are called \”temporarily captured flybys\” ” is equivalent to coming to Earth to “visit” and then leaving in a hurry.

The discovery of the 2024 PT5 asteroid has created conditions for humans to carry out a series of precise observations. Scientists have planned to mobilize optical telescopes and radar telescopes to observe this \”mini-moon\” to obtain information on its rotation, shape, surface material and material composition. Scientists speculate that this type of asteroid that orbits close to the Earth may have originated from the moon, and may be the sputter produced by a larger asteroid impacting the moon.

The orbital energy of the \”mini moon\” is close to that of the Earth. Imagine that if humans can discover these \”mini-moons\” far enough in advance, they will have the opportunity to launch spacecraft to capture them at low cost. For example, the spacecraft propulsion system can be used to exert force on asteroids, and by consuming a certain amount of fuel, they can be permanently left in orbit around the Earth and then transformed into an asteroid space station. Robots and astronauts can then be dispatched to land on the space station, or valuable samples of the asteroid can be brought back to ground laboratories for research and analysis. We can even use this asteroid as a test object to carry out space experiments such as asteroid defense and resource development and utilization.

The \”mini moon\” will visit the earth periodically. For example, according to model calculations, this timeThe 2024 PT5 asteroid will \”return\” to Earth in 2055. Humans may be able to prepare in advance and use the spacecraft propulsion system to change its orbit when it visits the earth, allowing this \”mini moon\” to stay permanently.

Nine days embrace the \”moon\” and the vastness of the galaxy. With the continuous development of aerospace technology, mankind\’s journey to dream of the stars will surely become more brilliant.

(The author is a researcher at the National Space Science Center, Chinese Academy of Sciences)

\”People\’s Daily\” (Page 17, October 15, 2024)