Avi Loeb, an astrophysicist at Harvard University, has published a paper claiming that some of the spherules he recovered from the bottom of the Pacific Ocean are from beyond the solar system.
Loeb's analyses were carried out using well-known techniques and state-of-the-art equipment, so there are no concerns that the analyses are faulty. Indeed, most of the spherules do appear to come from outside our own planet, as shown by their abundances of elements such as nickel, magnesium and manganese, which match those of meteorites.
However, a few of the spherules stand out because they have more unusual elemental compositions. These are named "BeLaU" particles by Loeb because they are rich in beryllium, lanthanum and uranium. Loeb rules out them being natural, terrestrial material, or extraterrestrial material from within the solar system, on the basis of their iron isotope compositions.
However, other experts have questioned Loeb's conclusions. They argue that the BeLaU spherules could have come from asteroids within our solar system, or even from the Marshall Islands, which were the site of 67 nuclear tests between 1946 and 1958.
More research is needed to definitively determine the origin of the spherules. However, for now, the evidence is not convincing that they are from beyond the solar system.