Potara Earth occasionally captures small asteroids in its gravitational pull, forming temporary companions known as mini-moons. One such event is happening in 2024 with the asteroid 2024 PT5. Discovered on August 7, 2024, by the Asteroid Terrestrial-impact Last Alert System (ATLAS), this small celestial object, roughly 33 feet (10 meters) wide, will temporarily orbit Earth from September 29 to November 25, 2024.
These mini-moons are a rare phenomenon, caused by a precise interaction between an asteroid's speed and proximity to Earth. For an object like 2024 PT5 to become a mini-moon, it must approach Earth at just the right velocity. If it is too fast, it escapes Earth's gravitational influence; too slow, and it may crash into the planet. PT5’s relatively slow velocity allows Earth’s gravity to pull it in, though it won’t complete a full orbit, behaving more like a "captured flyby."
Interestingly, this is not the first time Earth has gained a mini-moon. Similar events have been recorded in 2006, 2020, and as recently as 2022. These small bodies often follow paths similar to Earth’s orbit around the sun, such as those in the Arjuna asteroid group, of which PT5 is a member. These asteroids tend to follow orbits that closely resemble Earth's own, making them prime candidates for temporary capture. However, mini-moons like PT5 do not last long; after a few weeks or months, they usually escape back into space, resuming their heliocentric orbit around the sun.
Although PT5 will be too small and dim to observe with standard telescopes, it serves as a fascinating reminder of Earth's dynamic relationship with near-Earth objects (NEOs). NASA tracks around 28,000 such objects, which are defined as any body coming within 120 million miles of our planet. While PT5 poses no threat to Earth, NASA continues to monitor larger NEOs that could be hazardous, even testing planetary defense methods like the successful deflection of an asteroid in 2022.
Beyond their scientific curiosity, mini-moons also spark interest in the possibility of asteroid mining. Some asteroids contain valuable minerals and water, which could potentially be used as resources in future space exploration missions. Their temporary capture by Earth could provide a convenient opportunity to study them more closely.
After PT5 leaves Earth's gravitational pull in late November, it will return to orbit the sun and make another close pass by Earth in 2055. As our understanding of these temporary companions grows, so does our ability to detect and study them, deepening our knowledge of the objects that frequently wander through our cosmic neighborhood.