
For years, the space near Earth was assumed to be fairly well known, particularly in terms of detecting near-Earth objects (NEOs) like asteroids and debris. That perception is being turned on its head by new discoveries. According to a recent paper published in The Astrophysical Journal Letters, there could be an undiscovered population of “minimoons“—small natural satellites—around Earth. And what is interesting about these objects is that some of them seem to be debris from the Moon itself.
The research highlights the recently identified object 2024 PT5an asteroid-like body that shows lunar-like features such as orbital properties and compositional similarities with Moon rock. This finding by planetary scientist Teddy Kareta and his Lowell Observatory team opens up the thrilling possibility that numerous other such pieces are orbiting Earth in silence, leftovers from old lunar impacts.
What are minimoons and their role in space science
Minimoons are minor bodies temporarily held in Earth’s gravity. In contrast to the Moon, which is a natural permanent satellite, minimoons have transient orbits—occasionally staying within the gravitational clutches of Earth for weeks, months, or years before finally breaking free again into solar orbit.
Until recently, these objects were thought to be very rare. The first clearly established minimoon of possible lunar origin, Kamo’oalewa, was found in 2021. With the discovery of 2024 PT5, the story is emerging. Researchers are starting to see these objects not as oddities, but as possible members of a larger population that hasn’t been seen because they are too small and have too complicated, changing orbits.
New evidence suggests 2024 PT5 could be a piece of the moon
The identification of 2024 PT5 is especially noteworthy due to its possible lunar origin. Its path and spectral character—a method of determining an object’s composition from the manner in which it scatters light—effectively mimic those of rocks brought back to Earth by NASA’s Apollo missions. This heavily indicates that PT5 could be a piece that was ejected from the surface of the Moon, perhaps by a meteoric impact.
Teddy Kareta emphasised the importance of the discovery at the 56th annual Lunar and Planetary Science Conference, saying: “If there were only one object, that would be interesting but an outlier. If there’s two, we’re pretty confident that’s a population.”
In other words, the confirmation of a second minimoon with lunar properties supports the idea that such objects are more common than previously believed.
Understanding lunar debris: How high-energy impacts send moon fragments into Earth’s orbit
Lunar debris is usually created through high-energy impact events, in which meteoroids collide with the lunar surface and send debris into space. A portion of this debris may fall into the Earth’s sphere of gravitational influence, becoming temporarily captured. They have chaotic, highly elliptical orbits that set them apart from both standard NEOs and Earth’s main Moon. Simulations and tracking models imply that these fragments can be trapped for a few months to a few years, after which they will burn up in Earth’s atmosphere, escape Earth’s gravity, or be deflected by subsequent gravitational encounters.
What minimoons can reveal
The implications of minimoons from a scientific perspective are significant. Minimoons provide a one-of-a-kind chance to investigate the Moon’s impact record without sending complex sample-return missions to the surface of the Moon. By analysing the composition of the minimoons, scientists can determine the nature of the rock, the age of the rock, and possibly trace it to a particular crater or region of geology on the Moon.
This could greatly improve the knowledge of:
- Geological evolution of the Moon
- Rate and magnitude of lunar impact events
- Orbital dynamics of
Earth-Moon interactions
Kareta compared it to forensic science by saying: “It’s like discovering a crime scene has a completely new type of evidence you didn’t realise you had before.”
These pieces are actually natural sample-return missions already underway.
From sample return to space mining: The strategic value of minimoons
Aside from academic curiosity, minimoons also have significant potential for future missions of exploration. Because they are close and relatively slow-moving relative to other NEOs, they are prime targets for:
- Robotic spacecraft missions
- Sample return programs
- Experimentation with navigation and landing technologies for asteroid mining or deep space missions
They provide a valuable stepping stone to deep-space exploration while also facilitating new types of resource analysis and planetary defense testing.
2024 PT5 highlights the need for advanced detection methods
The detection of 2024 PT5 emphasises the necessity of more sensitive sky surveys and special observation programs. The majority of existing asteroid detection systems are optimized for discovering larger, brighter objects. Minimoons, being small and faint, need different methods and continuous monitoring in order to be discovered.
The development of this capability would greatly improve our knowledge of not just minimoons, but also the dynamic interaction between Earth and its cosmic environment.
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