Este artigo foi escrito originalmente em inglês.
Ler em Português
Sar2901 is a temporary mini-moon, a small object that got gravitationally captured into a brief, unstable orbit around the Earth-Moon system. Eventually, it will escape back into an orbit around the Sun. On September 2, 2026, the Minor Planet Center posted here the following statement:
“The object Sar2901 … [has] an orbit that is suggestive of either a mini-moon or an artificial object. The broader community seems to be split as to which is the most favored … The object has faded from view and is likely to only become accessible to observation in the mid-to-late November (2026) period. If/when observations are obtained in the November/December 2026 period, it will be plausible to determine the magnitude of any non-gravitational forces acting on the orbit, thus enabling a refined assessment about the nature of this object. Moreover, additional characterization observations are also likely to be taken in that same period.”
Sar2901 could be a small asteroid of natural origin which was temporarily captured by Earth-Moon gravity, or a discarded rocket stage, panel, or other hardware still orbiting the Sun on an Earth-like path, occasionally swinging back close enough to briefly re-enter a quasi-Earth orbit.
This second category has precedents. For example, the object J002E3, discovered in 2002, was eventually identified as the S-IVB third stage of the Apollo 12 Saturn V rocket, confirmed through spectroscopic analysis to show the signatures of titanium dioxide paint consistent with the rocket’s white coating. This particular mini-moon turned out to be NASA hardware from the 1970s.
The scientist Marshall Eubanks tweeted here that Sar2901 came close to Earth in the past, notably during the period of April 10–20, 1970. This period overlaps with the Apollo 13 launch on April 11, 1970, the explosion of its oxygen tank on April 13, 1970, and its splashdown on April 17, 1970. The specific candidate object being proposed as Sar2901’s true identity is a panel ejected during the Apollo 13 explosion. The oxygen tank explosion on April 14, 1970 blew off an exterior panel of the Service Module, which was documented at the time and even photographed by the crew. Sar2901 could also be one of the four panels of the Apollo 13 S-IVB (the Saturn V third stage) which were jettisoned as part of normal lunar module extraction procedures. This is another plausible debris source from the same mission, independent of the accident itself.
Current orbital data on Sar2901 is insufficiently accurate for running it backward in time to see whether the trajectory intersects with Earth in a way consistent with an object launched or ejected from an Earth-bound orbit around April 13, 1970, compared to an alternative trajectory which might be more consistent with a natural asteroid’s independent heliocentric orbit that just happened to pass near Earth around the same date coincidentally.
Distinguishing a piece of 56-year-old space debris from a genuine natural mini-moon requires precise orbital back-integration over decades and is sensitive to small perturbations. In particular, solar radiation pressure triggers a much larger non-gravitational acceleration for a lightweight metal panel than for a solid rocky asteroid of similar apparent brightness, making this acceleration one of the better discriminating clues. In addition, spectroscopic data — as was eventually obtained for J002E3 — could be used to match reflected light spectra against known spacecraft materials, such as aluminum, paint or titanium dioxide, rather than a natural surface composed of silicate or carbonaceous material.
Three years after the first interstellar object, 1I/`Oumuamua, was discovered, the same telescope in Hawaii, Pan STARRS-1, discovered the anomalous near-Earth object 2020 SO, which like 1I/`Oumuamua was pushed away from the Sun by solar radiation pressure without any signs of cometary outgassing. Ultimately, the spectrum of 2020 SO revealed that the surface is made of stainless steel, as expected for the Centaur upper stage used by NASA on the September, 20 1966 launch of the Surveyor 2 spacecraft.
Sar2901’s identity, whether it is Apollo 13 panels or unrelated natural asteroid that happened to pass by around the same time, is not yet resolved, and would need either better orbital back-integration data or spectroscopic follow-up attempting to match reflectance against Apollo-era materials, to move its detection from an “intriguing coincidence” to a status of “confirmed identification.”
It is important to separate a technological origin from a natural origin for space objects near Earth, because such studies provide a training data set for anomalous interstellar objects like 1I/`Oumuamua. As long as we are open minded to the possibility of alien probes visiting the inner solar system, we might discover the products of other technological civilizations in our backyard. There is nothing more important than such a discovery in fostering our own aspirations for interstellar travel.
Authorized publication by Dr.Avi Loeb
