The Sound of an Interstellar Meteor Might Have Just Been a Rumbling Truck

A 2023 expedition to the Pacific Ocean, searching for debris from a suspected extraterrestrial object, may have been looking in the wrong place. A new look at the infrasound data used to locate the point of impact suggests that they may have been confused by the rumblings of a truck driving past.

On 14 January 2018, a space rock hit the Earth’s atmosphere off the coast of Papua New Guinea. It was detected by what are mysteriously described as “US Government Sensors”, and given the catalogue entry “CNEOS 2014-01-08”. Based on the brightness of the fireball and its apparent speed, the physical rock likely survived without burning up completely. The observation was logged in a database kept by the Center for Near Earth Object Studies. Bolides like this can be a spectacular sight, when spotted by human eyes, but they are not rare; several are detected each week.

Extrasolar objects

A few years later, Oumuamua was discovered. Oumuamua was traveling at a high speed, along a path that showed it was not orbiting the Sun. Instead, it had come from interstellar space and was merely passing through. This was very exciting because it was the first time anybody had observed an interstellar rocky object, and so it attracted a lot of attention.

Some observations showed that Oumuamua’s path wasn’t steady, but kept making tiny changes. Most scientists agreed that this was almost certainly because of pockets of ice melting and jetting away in the Sun’s heat. This is a common phenomenon, that we often see happening with comets. More detailed observations and simulations showed that it had a long and skinny shape, more like a splinter than a boulder, which is very unusual among the asteroids and comets that we’re used to. But Oumuamua only really hit the mainstream press when a well-known and prestigious astrophysicist decided, in a surprising leap of logic, that all these details proved that it could be an alien spacecraft!

The Oumuamua discovery led many scientists to start searching for other interstellar objects. CNEOS 2014-01-08, with its high reported speed, looked like a promising candidate. The physicist who had made such a big deal about Oumuamua being artificial took a closer look at the bolide reports and concluded that it must have been traveling fast enough to be another extrasolar object. This claim was controversial, not only because the government sensors appear to be classified and so cannot be verified, but because meteor speeds are notoriously difficult to measure. Observers have mistakenly reported extrasolar meteors as far back as 1951!

But if CNEOS 2014-01-08 truly was from outside the Solar System, and we could find pieces of it, that would be an incredible discovery: The first actual geological samples from a planetary system outside our own!

The expedition

This is why an expedition was launched in 2023 to try and find it. The research team used seismic and infrasound data from seismic research stations in the area to try and find the exact place where the meteorite would have splashed into the sea. They identified two likely signals from Geoscience Australia’s Passive Seismic Network. The signals were recorded by Manus Island, Papua New Guinea (AU.MANU) and Coen, Queensland, Australia (AU.COEN), at around the same time that the fireball was detected. They triangulated a precise location based on those recordings, and sailed out to search the ocean floor.

The expedition was widely reported as a success, after they found “metallic spherules”. These spherules had an unusual composition, which the expedition leader said was proof of a possible extraterrestrial origin. Like the speed calculations, though, this interpretation was widely challenged. Specialists in other fields have weighed in to argue that there was nothing unusual about the debris, and that various natural and human processes could have created them (My personal favorite: 19th century pollution!). With so much doubt as to where the spherules came from in the first place, it’s probably not wise to say that they are of “extraterrestrial technological” origin.

The truck

The most recent challenge to the results of this expedition come from a team led by Dr Benjamin Fernando of Johns Hopkins University. Their report focuses on the seismic and infrasound data used to locate the impact site.

They noticed a number of problems with the expedition’s analysis, starting with the fact that none of the detections happened within 30 seconds of the fireball. But beyond that, these stations are located in the Pacific Ring of Fire, which is very tectonically active. They detect a great many earthquakes and other natural seismic events every day, and some of these happened at the same time as the meteorite impact. Separating the two signals is hard to do without distorting both of them. This adds a lot of error to any calculations based on those data.

Along with seismic data, these stations also have infrasound detectors, meant to detect and monitor nuclear weapons tests. But infrasound has a limited range, and is strongly affected by geography.

Fernando’s team concluded that only one station recorded an infrasound signal that could have come from CNEOS 2014-01-08, and that none of the seismic detections had anything to do with the bolide. Based on this, they believe that the expedition was looking in the wrong place, and that the debris they discovered had nothing at all to do with the 2014 bolide.

But their most damning claim is this: The strongest signal had an unusual pattern, lasting a long time and coming from a direction which changed halfway. They noticed that there is a road passing near the station, with a curve in it that matches the change in direction of the signal. They point out that the signals recorded by trucks driving that road are a far closer match than any natural event.

In other words, they believe that the expedition based its search location for an extraterrestrial meteorite on the noise of somebody in a truck going for a drive.

In their defense

It’s tempting to laugh at the researchers on the expedition, especially since their leader was a respected astrophysicist who has recently developed a reputation for having crackpot ideas about aliens. But I think there is value in investigating these questions.

It’s easy to get tired of cranks and fools wasting our time with conspiracy theories and crazy stories about abductions. And we should always be skeptical of any claims about aliens, given what we know about the physics of interstellar travel and the absurd scale of the Universe.

But most astronomers agree that life has to exist elsewhere in the Universe, and many think that it could well be intelligent and technologically capable, like us. Nobody’s saying that they can’t possibly exist, only that it’s extremely unlikely that they are over here!

So we should be skeptical of these reports. It’s good to not waste too much time studying them, when there are other mysteries that are far more likely to be true. But that doesn’t mean we should ignore the possibility altogether. It would be disastrous if, by some chance, it turned out to be real, and the scientific community had simply refused to acknowledge it! When new evidence comes in, we must revisit our assumptions and go back and check our previous conclusions. And it’s important that somebody do this even when we’re certain that they’ll get a negative result.

To learn more, visit https://hub.jhu.edu/2024/03/07/alien-meteor-truck/