When you think of moons, the image that likely comes to mind is our one and only Moon. But did you know Earth often hosts a handful of tiny, temporary moons — known as minimoons — that quietly orbit our planet before continuing their journey around the sun? Recent research suggests that at any given time, Earth may have at least six of these mysterious visitors.
In this blog, we’ll uncover what minimoons are, where they come from, why they’re so hard to detect, and what makes them so scientifically and commercially intriguing.
What Are Minimoons?
Simply put, minimoons are small, natural objects temporarily captured by Earth’s gravity. Unlike our Moon, which is a permanent satellite, minimoons only stick around for a short period — often a few months — before escaping back into orbit around the sun. These fragments are usually no bigger than a car and sometimes as small as a beach ball, making them incredibly difficult to observe from Earth.
According to a study published in the journal Icarus, a minimoon is any object that is temporarily bound to Earth, completes at least one revolution, and comes within roughly four times the distance between the Earth and the Moon during its orbit. These transient moons are part of a cosmic dance, continuously joining and leaving Earth’s gravitational embrace.
Where Do Minimoons Come From?
One of the most intriguing aspects of minimoons is their origin. For years, scientists believed most of them came from the asteroid belt — a region of space between Mars and Jupiter filled with rocky debris. These asteroids sometimes wander close to Earth and get caught in our planet’s gravity.
But recent studies challenge that assumption. Evidence now suggests many minimoons actually come from much closer to home — specifically, from our Moon itself. When meteoroids crash into the Moon’s surface, they eject debris. Some of this lunar material escapes the Moon’s gravity and ends up orbiting Earth for a while before moving on to circle the sun.
For example, the object Kamo’oalewa, discovered in 2016, appears to be a fragment of the Moon blasted away by an impact millions of years ago. Another object, 2024 PT5, also seems to have lunar origins. These findings imply that the Moon may regularly contribute to the population of minimoons.
How Many Minimoon Are There?
In their simulations, researchers estimated that, at any given moment, Earth may host around six minimoons originating from lunar debris. The number isn’t fixed; these objects come and go, constantly replenished by fresh fragments from the Moon and asteroids.
Robert Jedicke, the lead author of the Icarus study, described it as a sort of cosmic square dance — partners change, some leave, and new ones arrive. On average, a minimoon orbits Earth for about nine months before moving on.
However, it’s important to note that this estimate is highly uncertain. Many variables — such as the size and speed of the debris, and the frequency of lunar impacts — make it difficult to calculate precisely how many minimoons exist at any one time.
Why Are Minimoons Hard to Detect?
Despite the fact that minimoons are relatively common, we rarely see them. Their small size and high speed make them elusive to even the most advanced telescopes. Most minimoons measure between 3 to 7 feet (1 to 2 meters) in diameter, about the size of a car or SUV.
Detecting such tiny, fast-moving objects requires them to be close enough to Earth to appear bright in the sky. But when they are close, they also move quickly across the field of view, often leaving streaks rather than points of light in telescope images. These streaks are harder for computer algorithms to identify in large-scale sky surveys.
For example, the minimoon 2020 CD3 was only visible to the Catalina Sky Survey on two of the roughly 1,000 nights it was in range — showing just how challenging these detections can be. Still, every confirmed sighting improves our ability to track and predict future minimoons.
Why Do Minimoons Matter?
Beyond being a cosmic curiosity, minimoon have significant scientific and commercial implications.
Scientific Insights
Studying minimoons can teach us more about the Moon’s surface, impact events, and the mechanics of how debris travels through space. Understanding how lunar material is ejected and temporarily captured by Earth can also help researchers model asteroid impacts on Earth — vital knowledge for planetary defense.
Additionally, minimoons can offer clues about the early solar system and how planets and moons evolved over billions of years.
Commercial Potential
From a commercial perspective, minimoons present an exciting opportunity. Because they orbit close to Earth, they require less fuel to reach than other targets like asteroids in the main belt. This makes them ideal candidates for resource extraction missions, where companies could harvest water, metals, and other valuable materials.
If commercial space companies can develop reliable methods to capture and mine minimoons, it could open up a new frontier in the space economy.
The Future of Minimoon Research
As telescope technology and detection algorithms improve, we can expect to discover many more of these tiny, temporary moons. Every detection adds to our understanding and helps refine estimates of how many minimoons orbit Earth at any given time.
According to Jedicke, the initial estimate of six minimoons is almost certainly too high or too low — but that’s how science works. With every observation, we get closer to the truth.
Final Thoughts
Earth’s minimoons are fascinating reminders that our planet is part of an intricate, dynamic solar system. Though tiny and fleeting, these temporary moons hold clues to our past and potential keys to our future — both scientifically and commercially.
Next time you look up at the night sky, remember: the Moon you see might not be alone. Somewhere out there, a few minimoons are quietly circling, waiting to be discovered.
