Interstellar meteor fragments may have been found in the Pacific Ocean

An expedition to hunt for fragments of a possible interstellar meteor has found 40 tiny iron spherules on the sea floor – but whether they are truly interstellar is controversial 

A microscope image showing some of the spherules
Avi Loeb

Tiny flecks of an interstellar meteor may have been found at the bottom of the ocean. Researchers mounted an expedition to the Pacific Ocean just north of Papua New Guinea to hunt for fragments of the meteor, which fell to Earth in 2014, and they say their search has been successful – but other scientists remain sceptical.

Avi Loeb and Amir Siraj at Harvard University identified the meteor as potentially interstellar in 2019 based on its recorded velocity, which they claimed was fast enough to indicate that it hurtled into our solar system from interstellar space. The data they used came from classified US government sensors, so there wasn’t enough information to prove their claim, but the government released a statement confirming the high velocity. They nicknamed the object Interstellar Meteor 1, or IM1, although many astronomers remain unconvinced that it is truly interstellar.

Using the sparse data the government did release, Loeb and Siraj traced the area where the meteor exploded in the atmosphere, and Loeb and his colleagues headed out on a privately funded voyage. They dragged the sea floor under the area using a magnetic sled to pick up bits of iron, as well as a sieve similar to those used to pan for gold, and they have found 40 of what they say are fragments of IM1.

The fragments are in the form of tiny iron spherules, each less than a millimetre across. This in itself isn’t particularly surprising. “Micrometeorites should be found all across the sea floor due to their constant accumulation by the earth, so if you’re thorough enough you’re bound to find something,” says Alan Fitzsimmons at Queen’s University Belfast in the UK, who was not involved with this work.

However, Loeb says that they only found these spherules in the area under where the explosion is thought to have happened, not in the other spots they visited as controls. He also claims to have found strange compositions upon preliminary analysis.

“The composition didn’t look like anything that is Earth-like – I will not go into detail until we do the complete analysis on land, but we find composition patterns that deviate from what was reported in the past,” he says. “Some elements are abundant that are extremely rare, and some are not present at all.”

One of the elements that seems to be missing is nickel, which usually makes up about 5 to 10 per cent of iron meteorites. That may be unusual, but it isn’t enough to convince some astronomers that the spherules are interstellar. “The allusion is that it’s not like the other spherules, but we don’t know that yet – and in fact there’s a big dispersion in nickel abundance in the others, especially those in the ocean,” says David Jewitt at the University of California, Los Angeles.

Loeb and his colleagues plan to do a more detailed analysis of the spherules as soon as they get back from their expedition, so there should be results within weeks. If they show that these tiny marbles have a very different makeup to those from within the solar system, or that they are far older than the solar system, that could finally be conclusive proof that IM1 truly is interstellar – and that these are the first fragments of an interstellar rock ever recovered.