Earth’s Mini-Moon 2024 PT5: A Brief Visit from a Lunar Relic

Earth’s Mini-Moon: Asteroid 2024 PT5 Overview

Earth recently hosted an asteroid known as 2024 PT5, described as a “mini-moon.” It entered Earth’s orbit on September 29, 2024, and departed on November 25, 2024. Analysis shows that this asteroid may originate from material ejected from Earth’s true moon during a past collision.

Origins and Composition

The leading theory for moon formation is called the “giant impact hypothesis,” which suggests that a massive collision occurred around 4 billion years ago, leading to the formation of the moon from cooled, ejected material. According to Carlos de la Fuente Marcos, the lead author of the study, multiple lines of evidence indicate that 2024 PT5 might be a lunar fragment or a large boulder from the moon.

Spectra analysis of 2024 PT5 shows that its chemical composition closely matches samples collected during historic moon missions, including NASA’s Apollo missions and the Russian Luna missions.

How Earth Captured 2024 PT5

2024 PT5 came from the Arjuna asteroid belt, which has a similar orbital path to Earth, located about 93 million miles from the sun. Marcos explained that some objects from this belt can closely approach Earth, allowing min-moons like 2024 PT5 to enter our orbit.

To be considered a mini-moon, an asteroid must approach Earth within approximately 2.8 million miles at a speed of less than 2,200 miles per hour. The capture of 2024 PT5 began when it met these criteria and will end when its orbit is disturbed by the sun’s gravity.

Mini-Moon Engagements

There are two main types of mini-moon events: long stays, where an asteroid completes one or more orbits, and short engagements, where it does not complete a full revolution. 2024 PT5 belonged to the latter category, having a brief tenure around Earth.

After leaving, 2024 PT5 returned to the Arjuna asteroid belt, joining other objects.

Future Studies

The orbit of 2024 PT5 has been well established thanks to data from the Teide Observatory. NASA plans to study this asteroid further during another close approach on January 9, 2025.

The findings about 2024 PT5 help scientists understand that other bodies in the Arjuna asteroid belt might also have lunar origins. Marcos summarized by saying that mini-moons like 2024 PT5 come and go, with more captures expected soon, thanks to advances in Near Earth Object surveys.

The research findings are part of a paper accepted for publication in the journal Astronomy & Astrophysics.