From https://iopscience.iop.org/article/10.3847/2515-5172/ad03f9
Quote:
Abstract
Chemical composition for spherules recovered from the search area of CNEOS 2014-01-08 in the Pacific Ocean has been recently released. A three-order of magnitude difference from CI-chondrites has been identified for elements beryllium, lanthanum and uranium in five samples. The lack of consensus regarding atmospheric survival and precision of path estimates motivate an examination of possible contaminants. Contents of nickel, beryllium, lanthanum and uranium are examined in the context of a known anthropogenic source of contamination, and found to be consistent with coal ash as suggested from a publicly available coal chemical composition database (COALQUAL). The meteoritic origin is disfavored.
To the best of my knowledge, all meteorites are extra-terrestrial in origin and made up of the remnants of previous stars and of supernovas. It should not be at all surprising if material ejected or created by various processes such as supernovas and stellar collisions from elsewhere in the universe could reach the Earth as meteorites. As far as I can see, the only way to distinguish these from the material left over from the creation of the solar system would be by their measured trajectories.
We shouldn't expect to find evidence of alien intelligence in them, though. Even if some of the previous generation of stars from which the Earth had planets that were occupied by intelligent life, their debris would be an extremely tiny fraction of the debris from the previous stars and planets even if it all survived a supernova that flung it out in space, only a very tiny fraction of that debris would be likely to reach Earth.
Also, there is a hypothesis that it would take at least a third generation of stars before intelligent life would even be possible. Think about it -- the first generation of stars could hardly have had planets -- elements heavier than lithium would need to have been created by processes such as stellar nucleosynthesis, supernova nucleosynthesis, or the collision of heavy stars -- not even carbon existed back then. So intelligent life would have to come later.
As I understand it, the second generation of stars did not yet have a great abundance of elements heavier than lithium available when they formed and would, by necessity, be relatively small stars and a great many probably remain to this day. The material available to form their planets was very limited.
So figure that it would need a third or later generation star.
Another possibility for debris from extra terrestrial civilizations would be if they sent out probes such as a very limited number of our probes. After however many million years, it wouldn't be surprising if they came within one or two light years of another star, but the chance of reaching another civilization would be vanishingly small.
Or perhaps there was a collision between a planet with intelligent life and a very large asteroid that knocked part of the planet away. The portion of the debris that would be of the civilization would be tiny. It would also be likely to be unable to reach escape velocity to escape its star -- look at our moon as an example.
So while material from outside our solar system could reach us, the presence of debris from an alien civilization would be vanishingly small.