A glowing metal ring crashed into the Earth. No one knows where it came from

It’s been more than a week since reports first emerged of a “glowing ring of metal” falling from the sky and crashing near a remote village in Kenya.

According to the Kenyan Space Agency, the object weighed 1,100 pounds and was more than 8 feet in diameter when measured after its Dec. 30 landing. A few days later, the space agency confidently announced that the object was part of space debris, saying it was a ring that had broken off from a rocket. “Such objects are typically designed to burn up as they reenter Earth’s atmosphere or fall over unoccupied areas such as the oceans,” the space agency told The New York Times.

Since those initial reports were published in the Western media, a small group of dedicated space trackers have been using open-source data to try to identify exactly which space object fell in Kenya. So far, they have not been able to identify the rocket launch that could account for the large ring.

Now some space researchers believe that the object may not have come from space at all.

Did it really come from space?

Space is increasingly crowded, but large chunks of metal from rockets don’t usually fly into Earth orbit undetected and untracked.

“The ring was thought to be space debris, but the evidence is slim,” wrote Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. McDowell is highly regarded for his analysis of space objects. “The most likely space-related possibility is the re-entry of the SYLDA adapter from the Ariane V184 flight, object 33155. However, I am not entirely convinced that the ring is space debris at all,” he wrote.

Another prominent space explorer, Marco Langbroek, believes it is plausible that the ring came from space, so he is further investigating objects that may have returned at the time of the discovery of the Kenya site. c blog post written on Wednesday he noted that in addition to the metal ring, other fragments that appeared consistent with space debris—including material that looked like carbon sheaths and insulating foil—were found several kilometers from the ring.

Like McDowell, Langbrook concluded that the most likely source for the object was Ariane V launch this happened in July 2008, when the European rocket lifted two satellites into geosynchronous transfer orbit.

The Ariane V rocket was a rather unique rocket in that it was designed with the capacity to launch two medium-sized satellites into geostationary transfer orbit, a destination far more popular in the late 1990s and early 2000s than it is today. To accommodate both satellites, the SYstème de Lancement Double Ariane (SYLDA) envelope was placed over the lower satellite to support mounting a second satellite on top of it. During the 2008 launch. that SYLDA projectile was launched into a 1.6-degree inclined geosynchronous transfer orbit, Langbroek said.

Could it have come from a European rocket?

Over the years, this object has been tracked by the US military, which maintains a database of space objects so that active spacecraft can avoid collisions. Due to the lack of tracking stations near the equator, this object is observed only periodically. According to Langbroek, its last observation took place on December 23, when it was in a highly elliptical orbit, reaching perigee only 90 miles (146 km) from Earth. This was a week before an object crashed in Kenya.

Based on his modeling of the possible re-entry of the SYLDA projectile, Langbroek believes it is possible that the European object may have landed in Kenya around the time it was observed to re-enter.

However, an anonymous X account using the handle DutchSpace, which despite anonymity has provided reliable information about Ariane launch vehicles in the past, post a topic this indicates that this ring cannot have been part of the SYLDA shell. With images and documentation, it seems clear that neither the diameter nor the mass of the SYLDA component matches the ring found in Kenya.

Additionally, Arianespace employees said newspaper Le Parisien on Thursday that they don’t believe the space debris is connected to the Ariane V rocket. Basically, if the ring doesn’t fit, you have an excuse.

So what was it?

This story originally appeared on Ars Technica.