An artist's depiction of an asteroid circling Earth. Getty Images
A mini-moon, named 2024 PT5, has been orbiting Earth for the last two months but is now preparing to leave our planet's orbit as it heads on a decades-long journey through the solar system. This bus-sized asteroid, which is currently about 2 million miles (3.2 million kilometres) away from Earth, is being pulled away by the sun's gravity.
The asteroid was first spotted by the Asteroid Terrestrial-Impact Last Alert System (ATLAS) on August 7, 2024, and was captured by Earth's gravity on September 29. Since then, it has completed one full orbit around Earth and is now set to move away as it falls under the sun's influence. This phenomenon, where objects temporarily orbit Earth, is referred to as a "mini-moon."
While the exact origin of this mini-moon is uncertain, scientists suspect it may be a chunk of the Moon itself. The theory is that it could have been ejected from the Moon centuries ago after being hit by an asteroid. Josh Handal, a program analyst at NASA's Planetary Defense Coordination Office, wrote in a blog post, "Given the similarity between asteroid 2024 PT5's motion and that of our planet's, scientists suspect that the object could be a large chunk of rock ejected from the Moon's surface after an asteroid impact long ago."
Although similar orbits have been found for rocket debris from past space missions, analysis of 2024 PT5's motion suggests it is more likely to be of natural origin, rather than a piece of a rocket.
Despite leaving Earth's orbit, this mini-moon is not gone for good. In January, it will swing by Earth again, getting much closer than its current position—about 1.1 million miles (1.78 million kilometers) away, traveling at twice its current speed. This will be a farewell pass before it continues its orbit around the sun. NASA plans to track this flyby using the Goldstone Solar System Radar antenna in California's Mojave Desert for a week.
After this pass, asteroid-watchers will have to wait until 2055 to catch another glimpse of the mini-moon as it returns for another brief lap around Earth.
While mini-moons may sound like space curiosities, they have practical importance too. Research indicates that these rocks could contain valuable minerals and water, which might one day be used for rocket fuel. This makes them interesting targets for future space missions, especially for companies looking to mine asteroids and explore new resources in space.
