A sensational claim made last year that an ‘alien’ meteorite hit Earth near Papua New Guinea in 2014 got its first in-person airing with the broader scientific community on 12 March. At the Lunar and Planetary Science Conference in The Woodlands, Texas, scientists clashed over whether a research team has indeed found fragments of a space rock that came from outside the Solar System.

The debate occurred at a packed session featuring Hairuo Fu, a graduate student at Harvard University in Cambridge, Massachusetts, who is a member of the team that found the fragments. Team leader Avi Loeb, an astrophysicist at Harvard who did not attend the conference, has made other controversial claims about extraterrestrial discoveries. Many scientists have said that they don't want to spend much of their time analysing and refuting these claims.

During his presentation, Fu described tiny metallic blobs that Loeb’s expedition dredged from the sea floor near Papua New Guinea last year, and said that the spherules have a chemical composition of unknown origin1. He then faced questions from a long line of scientists sceptical of the implications of extraterrestrial material. “At the very least, it is something different from what we know,” Fu responded.

New work questions the team’s findings. In a manuscript posted on the arXiv preprint server on 8 March2, ahead of peer review, a researcher argues that the debris collected by Loeb and his co-workers is actually molten blobs generated when an asteroid hit Earth 788,000 years ago.

“What they found has all the characteristics of microtektites — little pieces of melted Earth that came from this impact,” says preprint author Steve Desch, an astrophysicist at Arizona State University in Tempe.

Whoops.

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