On Jan. 8, 2014, a meteor raced through Earth’s atmosphere off Papua New Guinea, exploded into a fireball over the ocean, and disappeared. That would have been the end of it. Except for Harvard astronomer Abraham “Avi” Loeb, who in 2019 analyzed data from low-frequency sound sensors run by the U.S. Department of Defense capable of detecting the tracks of meteors. Based on the object’s apparently unusual trajectory and immense speed, Loeb and colleagues concluded it was the first documented object from outside the solar system to encounter the Earth. They dubbed it IM1, the “I” standing for “Interstellar.”
Most meteors vaporize in the air; solid fragments that reach the ground, known as meteorites, are rare. But finding anything from IM1 could be scientific coup. Loeb, a sometimes controversial scientific superstar and best-selling author of a book about the search for extraterrestrial life, went to work organizing a search expedition.
One problem: the record of the airborne shock wave left room for a wide margin of error regarding where anything may have fallen into the ocean―an area of some 120 square kilometers. To help refine the data, the group turned to an earthquake seismometer at a naval base on the Papua New Guinea island of Manus, the nearest land. In its records, they found an earthquake signal matching the time of the meteor―an apparent quivering of the Earth’s surface as the airborne wave hit. Bolstered by this, they zeroed in on a 16-kilometer-square strip of seabed about 50 miles north of the island.
In June 2023, Loeb’s team scoured the ocean bottom with powerful magnets towed under a ship. They found no meteorites, but did dredge up some 700 spherules―tiny droplets solidified from molten material, which sometimes rain down when a meteor burns up. Not only that—they said some spherules had ratios of elements not found on Earth or any other planet in the solar system. And even more than that: “Another possibility is that this unfamiliar abundance pattern may reflect an extraterrestrial technological origin”―as Loeb and others speculated, bits of an alien spacecraft.
While even the U.S. Space Command agreed the object was probably interstellar, many scientists doubted that Loeb had really found its remnants, much less that it was something made by aliens. Among them: a group of planetary scientists led by Benjamin Fernando of Johns Hopkins University. They decided to look into not the spherules themselves, but the earthquake record. For this, they recruited Göran Ekström, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory known for studying unusual seismic events.
The group reported their results at the March Lunar and Planetary Science Conference. And a ruckus ensued in the scientific community and in media.
In the seismic station’s records, Ekström found the purported meteor-inspired signal right where it was supposed to be. Then he looked further and found that the records contained hundreds of other tremors in the weeks before and after, and many of them looked similar to that of the meteor. They were not characteristic of the small earthquakes that commonly shake this region, located on the Pacific Ring of Fire, where tectonic plates are constantly rubbing shoulders.
The signals consisted of so-called Rayleigh waves, high-frequency motions that travel on or just under the surface, and die out quickly as they radiate from their source. These can be generated by earthquakes, but also by human activities, including explosions, electrical signals and vehicles. The sources of these ones seemed to be moving, not stationary. Moreover, they appeared in a definite pattern: several per hour, almost invariably between 5am and 11pm local time.
The team checked a Google Earth map showing the seismometer and its environs. It was just off the main road to the harbor, near the Manus Navy Health Center. The center seemed to be a locus of activity, with the signals moving back and forth from it, southwest to north―the same orientation as the road. Ekström’s conclusion: the seismicity was coming from trucks bumping along the irregular surface of the road, mostly in daytime, stopping at the health center to deliver or pick up people or supplies, then going back where they came from. That included the purported tremor from the meteor explosion.
“The signal Harvard used to locate the impact is totally bogus,” said Ekström. “There’s a rich literature on the kind of seismicity produced by vehicles. When you drive along a bumpy road, you’re generating waves that have all the characteristics of the ones we saw.” The clincher, he said: the daily ebb and flow of the signals. “Meteors, earthquakes, landslides, whatever natural phenomena, they don’t watch the clock. People do.”
The team also reanalyzed the airborne sound waves, and identified what they say is a more likely location for the meteor to have blown up, some 100 miles north of the Harvard search area. “The fireball location was actually very far away from where the oceanographic expedition went to retrieve these meteor fragments,” said Fernando in a press release. “Not only did they use the wrong signal, they were looking in the wrong place.” The group argues that the recovered spherules are probably remnants of ordinary meteorites, possibly mixed with contaminants from the Earth. “We strongly suspect it wasn’t aliens,” Fernando added.
Loeb quickly struck back. Pointing out that Fernando’s team had yet to publish their results in a peer-reviewed journal, he wrote a rebuttal on the popular website Medium and another on the scientific site arXiv. He said his team had primarily used the airborne sound data, and would have searched basically the same area with or without the seismic data. He told the Washington Post that the critics “did not collect material, they did not analyze anything. They just sit on their chairs and express their opinions.” Loeb said that when he gets enough funding, he will resume the search for fragments.
As a result of the seismic study, Loeb was widely razzed by media including The New York Times. But some scientists told Scientific American that even if the material was not interstellar, the search could produce useful science. Eleanor Sansom, a planetary scientist at Australia’s Curtin University and coauthor of the seismic study, said that tracking incoming meteors is a fledgling field. “Trying to work out how things come through our atmosphere, where they’re coming from and where they’re going to land is really exciting,” she said.
“They should have talked to a seismologist the first time,” said Ekström. That said, he added, “People love this stuff, everything about aliens and meteors and meteorites. If they do go back, I hope they find something interesting.”
