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Unlike most planets in the solar system, Earth usually has only one permanent satellite. However, it occasionally captures passing asteroids, creating temporary “mini‑moons.” Over the past few decades, four such objects have been documented.
Asteroid 2022 NX1 (5–15 m diameter) first orbited Earth for 98 days from October 1980 to January 1981. After a brief 19‑day interlude, it returned for a second, 29‑day stint. In 2022 it was drawn back into Earth’s gravity for a single 21‑day capture, marking the first known near‑Earth object to undergo multiple captures in one close‑encounter episode.
In a similar event, Asteroid 1991 VG (≈10 m) was briefly trapped from November 1991 to April 1992. When it was observed again in May 2017, its orbit closely matched Earth’s heliocentric path, so it was no longer considered a mini‑moon.
Asteroid 2006 RH120 proved the most enduring. From late May 2006 to late July 2007, the 5‑m asteroid orbited Earth three times, remaining in a stable, temporary orbit for over a year.
More recently, Asteroid 2020 CD3 (≈1 m) was detected in February 2020. Scientists estimated it had been looping around Earth for about a year before being flung back into interplanetary space in early March 2020.
Scientists are still piecing together the dynamics that allow asteroids to be temporarily held by Earth’s gravity. The key factor is gravitational perturbation—small shifts in an object’s trajectory caused by the gravitational influence of other bodies.
For example, Asteroid 2024 PT5 was initially projected to be caught by Earth in September 2024. NASA’s observations, however, show its orbit around the Sun lies too far from Earth for capture. If future perturbations bring it closer, Earth’s gravity could indeed draw it in.
The Moon stabilizes Earth’s axial tilt and moderates seasonal extremes, but the temporary mini‑moons are too small and distant to affect our planet’s climate or orbital dynamics significantly.
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