An asteroid near Earth could become a temporary moon, then a crash risk
Scientists have recently identified a small asteroid, designated 2022 RD2, which has the potential to become a temporary mini moon of Earth before shifting onto a trajectory that could pose a hazard later in the century. This asteroid belongs to a rare class known as Arjunas, characterized by their orbits that closely resemble Earth’s and their ability to drift near our planet at low speeds. Such conditions allow Earth’s gravity to capture these asteroids temporarily, leading researchers to classify them as mini moons. NASA has placed 2022 RD2 on its risk list for potential impacts, although the agency’s Center for Near-Earth Object Studies has differing views on its future trajectory. If current predictions are accurate, 2022 RD2 could transition from being a near-Earth object to a temporary moon, and eventually to a potential collision risk—all within a single lifetime.
A team of astronomers from the Universidad Complutense de Madrid has analyzed the asteroid’s orbit and found it to be particularly unstable, with a Lyapunov time of less than 20 years. This means that small gravitational influences can significantly alter its path in a relatively short period. Their findings, published in the *Research Notes of the American Astronomical Society*, suggest that 2022 RD2 could enter a temporary orbit around Earth between 2043 and 2044, allowing it to be captured as a mini moon for several months. The researchers have applied standard criteria for such captures, including close approaches and a reduction in relative speed, to support their predictions. Following its brief stint as a mini moon, the asteroid’s trajectory is expected to become increasingly erratic, with some simulations indicating possible collision paths beginning around 2080. However, NASA’s models suggest that the odds of a collision are less than 0.1 percent, and even in the unlikely event of an impact, the asteroid’s small size—comparable to a three-story building—would likely result in minimal damage.
The Arjuna asteroids, including 2022 RD2, have garnered interest from scientists due to their accessibility for potential space exploration and commercial ventures, such as mining. The researchers believe that some of these asteroids may even be remnants of lunar debris from impacts on the moon. While 2022 RD2 is expected to remain a natural object, its origins and composition are still largely unknown, as only a few Arjunas have been studied in detail. The unique challenge posed by these near-Earth objects lies in their short visibility windows, making them difficult to observe. As the study of this population is just beginning, scientists are eager to gather more data to understand their potential risks and benefits better.
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Scientists have spotted a small asteroid that may circle Earth as a
mini moon
before shifting onto a path that could make it a hazard later in the century.
The
asteroid
, known as 2022 RD2, belongs to a rare class of
space
rocks called Arjunas. These objects travel around the
sun
on orbits that closely match Earth’s and sometimes drift near the planet at unusually low speeds. That sluggish pace can allow Earth’s gravity to trap them for a short time, creating what researchers call mini moons.
NASA
has calculated the asteroid’s orbit and placed it on its
risk list
for potential impacts, though the agency’s Center for Near-Earth Object Studies has reached somewhat different conclusions about the asteroid’s future trajectory.
If these predictions hold, 2022 RD2 could become one of the few known asteroids to shift from near-Earth object to temporary moon and later to a potential crash risk — all within a single lifetime.
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A team of astronomers in Madrid says 2022 RD2 follows an especially unstable path. It has a Lyapunov time — a measure of how quickly an orbit becomes unpredictable — of less than 20 years, much shorter than that of most near-Earth asteroids. That rapid change means small gravitational nudges can push the rock onto dramatically different routes over just a few decades.
Their
findings
appeared this week in
Research Notes of the American Astronomical Society
. The paper’s authors, brothers Carlos and Raúl de la Fuente Marcos of the Universidad Complutense de Madrid, have previously reported on the “quasi-moon”
2025 PN7
and the mini-moon
2024 PT5
, which briefly orbited Earth last year.
An image of the asteroid 2024 PT5, which became a temporary mini moon last year.
Credit: Two-Meter Twin Telescope / Light Bridges / Instituto de Astrofísica de Canarias
A key distinction, they note, is that mini moons get briefly captured by Earth’s gravity. But 2025 PN7 is more of a stalker, merely following Earth on its travels around the sun without becoming a true satellite.
The
Arjunas
interest researchers because of their scientific and practical potential, Carlos told Mashable.
“On the one hand, they are easier to access than other asteroids, so they can be used to test space technology or even to attempt commercial ventures on them such as mining,” he said. “On the other hand, some of them are suspected lunar debris resulting from present-day impacts on the moon.”
Simulations suggest 2022 RD2 could slip into a temporary orbit around Earth between 2043 and 2044, becoming a mini moon for several months. The team applied standard criteria for temporary captures: a close approach, a reduction in relative speed, and a period during which Earth’s gravity exerts enough control to form a true orbit.
After 2022 RD2 leaves Earth’s neighborhood, its path appears to grow more erratic. Some possible trajectories include collision paths beginning around 2080, according to the paper.
But NASA’s models put
potential impact
dates even later and estimate the odds at less than 0.1 percent, said Davide Farnocchia, a navigation engineer with the center. The asteroid is also relatively small, perhaps the size of a three-story building.
“So it wouldn’t cause any significant damage even in the unlikely case it were on an impact trajectory,” Farnocchia told Mashable.
Many recent mini moons and quasi-moons appear to belong to the Arjuna population — a loose cluster of Earth-like objects that trail our planet along its path around the sun. Their origins and composition remain largely unknown because only a few have been studied in detail. Some show similarities to the
actual moon
, Carlos said, but scientists need more data.
Although some small objects near Earth turn out to be old spacecraft or rocket boosters, the researchers say 2022 RD2 is almost certainly natural. And while their projections don’t confirm a future collision, they can’t yet rule it out.
“The study of this population is just beginning,” Carlos said. “Paradoxically, being so close to us, they are comparatively difficult to study, as many of them have short visibility windows and far between.”
