Earth to gain a temporary triple mini-moon as asteroid 2022 RD2 returns in 2043–2044

Astronomers have discovered that asteroid 2022 RD₂ will become a temporary companion to Earth not once, but three separate times during 2043 and 2044. This small Apollo-type asteroid, only 5–11 m (16–36 feet) wide, belongs to a population of near-Earth objects known as Arjunas — bodies whose orbits closely match Earth’s own.

Numerical simulations published in Research Notes of the American Astronomical Society in November 2025 show that 2022 RD₂ will enter Earth’s gravitational sphere of influence three times: from November 12 to December 12, 2043; again from February 29 to May 21, 2044; and finally between July 10 and July 29, 2044. During each of these intervals, it will act as a mini-moon, temporarily orbiting our planet before the Sun’s gravity pulls it away again.

The triple capture sequence stands out because no other known asteroid has been predicted to perform such a pattern within a single year. Previous mini-moons like 2006 RH₁₂₀ and 2020 CD₃ orbited Earth once before escaping. For 2022 RD₂, the dynamic is more complex: each capture is short, lasting from a few weeks to several months, and all three occur in rapid succession.

These transient events happen when an asteroid approaches at very low speed, typically less than 1 km/s (0.6 mi/s), and passes inside one Hill radius of Earth, about 0.01 AU. Inside this distance, Earth’s gravity can temporarily dominate the Sun’s, creating a brief natural satellite.

During each of its three predicted captures, 2022 RD₂’s energy relative to Earth will turn negative, meeting the standard definition of a temporary satellite. If the Sun’s gravity were somehow removed, the asteroid would remain bound to Earth indefinitely.

Chaotic path and unstable future

The orbit of 2022 RD₂ is remarkably Earth-like. It travels around the Sun at a distance of about 1.033 AU, with a low eccentricity of 0.0355. Its inclination is small, keeping it almost in the same plane as Earth’s orbit. This makes close approaches slow and frequent, but it also creates instability.

The asteroid’s Lyapunov time, the interval over which its motion remains predictable, is under 20 years. In dynamical terms, that means its orbit is chaotic. Small perturbations from Earth, the Moon, or even Venus can drastically alter its trajectory. The research team tested 1 000 slightly different orbits (or clones) and found that all underwent the triple capture, but after that, their futures diverged rapidly.

Once 2022 RD₂ escapes its third capture in mid-2044, it will drift into an unstable phase, potentially shifting into a “virtual impactor” orbit. According to the Jet Propulsion Laboratory’s Sentry monitoring system, there is a 0.097 percent probability of a collision with Earth between 2080 and 2124, corresponding to 101 virtual impact events.

If such an impact ever occurs, it would be minor. An asteroid this size would release energy comparable to a small airburst, far below the threshold for regional damage. Still, events like this help scientists refine models for how small asteroids interact with Earth’s gravity and atmosphere.

Because of its tiny size and faintness, its absolute magnitude is H = 28.6 ± 0.3—2022 RD₂ is invisible to all but the most powerful telescopes. It was discovered by Pan-STARRS 2 in Haleakalā on September 2, 2022, based on 45 observations over 84 days. Future detections will be needed to keep track of it as it approaches again.

The Arjuna asteroids: quiet wanderers of Earth’s path

The Arjuna group occupies a region of near-Earth space where orbits are nearly identical to our planet’s. These objects complete one revolution around the Sun in about one year, maintaining a 1:1 orbital resonance with Earth. Because of that synchrony, their motion relative to Earth is unusually slow, often less than 1 km/s (0.6 mi/s), making temporary captures possible.

Some Arjunas trace horseshoe orbits around Earth’s position, looping ahead and behind the planet over centuries. Others act as quasi-satellites, staying close to Earth while technically remaining in solar orbit. A few, like 2022 RD₂, are caught for a time as mini-moons.

Arjuna asteroids have a special scientific importance. Their gentle approaches mean they can be reached with small amounts of energy, making them ideal targets for spacecraft missions. A probe could rendezvous with such a body using less fuel than is required to reach the Moon, perform sampling, and return before the asteroid escapes.

The Arjunas are also thought to form a transitional population between the main asteroid belt and Earth-impacting meteoroids. Because they cross Earth’s orbit repeatedly, they provide a natural laboratory for studying how gravitational resonances and planetary encounters shape near-Earth space.

However, their Earth-like orbits also make them difficult to discover. They often appear close to the Sun in the sky and are faint; many are smaller than 20 m (65 feet). Upcoming wide-field surveys like the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will likely reveal many more in the coming decade.

How temporary satellites form and vanish

A temporary satellite capture occurs when an asteroid’s relative energy with respect to Earth becomes negative, and its distance drops below one Hill radius. The effect is strongest when the approach velocity is low. The asteroid then enters a looping trajectory around Earth before escaping back into solar orbit.

Because the Sun’s gravitational pull remains strong even within Earth’s Hill sphere, these orbits are not closed ellipses but complex three-body paths. The asteroid can complete several loops, shift direction, or appear to orbit backward before it departs.

For 2022 RD₂, the simulations show three such episodes. Each begins with a slow approach from ahead of Earth in its orbit, followed by capture and release a few weeks later. The third capture in July 2044 will be brief but complete, crossing the threshold between quasi-satellite and true mini-moon status.

These dynamics are not unique to Earth. Other planets, such as Jupiter and Mars, also experience temporary captures, but Earth’s smaller gravitational field and the stabilizing influence of the Moon make them rarer and shorter-lived here.

Studying such events helps scientists understand how gravitational chaos operates in the Earth–Moon–Sun system. It also aids mission planners in identifying natural low-energy gateways between Earth orbit and the broader Solar System.

Why 2022 RD₂ matters

The discovery of a future triple mini-moon series shows that even small asteroids can display surprisingly complex gravitational behavior. Each capture reveals the delicate balance between Earth’s pull and the Sun’s, and how a few metres per second can decide whether an object becomes a satellite, a passerby, or a future impactor.

These events also demonstrate that the region around Earth is dynamically active. Our planet is not isolated in space—it continuously interacts with a shifting cloud of near-Earth objects whose orbits evolve on decadal timescales. 2022 RD₂ is one of the clearest examples yet of how these interactions unfold.

The next decades will allow astronomers to test this prediction directly. If confirmed, the triple mini-moon sequence will mark one of the most complex temporary satellite captures ever recorded. Radar observations, optical tracking, and detailed numerical modeling will all play a role in verifying its behavior.

Mini-moons like 2022 RD₂ are reminders that the frontier of celestial mechanics lies close to home. The delicate gravitational choreography between Earth, the Moon, and the Sun still holds surprises, even for objects only a few metres across.

References:

¹ Rapid Dynamical Evolution in the Arjuna Asteroid Belt: Apollo 2022 RD₂ Goes from Mini-moon to Virtual Impactor in About 40 yr – Carlos de la Fuente Marcos and Raúl de la Fuente Marcos – Research Notes of the American Astronomical Society – November 2025 – https://iopscience.iop.org/article/10.3847/2515-5172/ae2001#rnaasae2001s4 – OPEN ACCESS

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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