Our solar system does not exist in isolation. It formed within a stellar nursery along with hundreds of sibling stars, and even today has the occasional interaction with interstellar objects such as Oumuamua and Borisov. So it’s reasonable to presume that some interstellar material has reached Earth. Recently, Dr. Avi Loeb and his team gained significant attention with a study proposing that they had found evidence of interstellar material on the ocean seabed. However, a new study challenges this claim, suggesting a more local origin for the discovered material.

The original study was based on a 2014 meteor that entered the Earth’s atmosphere off the coast of Papua New Guinea. The trajectory of this meteor led researchers to speculate that it may have had an extraterrestrial origin. Subsequently, the team led by Dr. Loeb examined the seafloor near Papua New Guinea and discovered small, iron-rich spheres known as spherules. Detailed analysis of the spherules’ composition revealed an unusual isotope distribution that hinted towards an interstellar origin.

Nevertheless, there are some important caveats to consider. Firstly, the exact trajectory of the 2014 meteor is not precisely determined, casting doubt on the direct link between the spherules and this specific extraterrestrial object. Secondly, the presence of “unusual” isotopes in these spherules is not unique to interstellar origins, as demonstrated by the wide variation in iron isotope ratios within our solar system. The new study reveals that the isotope ratios of the spherules fall well within the established range for solar system objects, making the likelihood of an interstellar origin less than 1 in 10,000.

Further investigation led the researchers to explore the possibility of a local impact event as the source of these spherules. They identified a known impact that occurred 790,000 years ago in the region, causing what is known as the Australasian tektite strewn field. By examining additional isotope ratios, they concluded that the composition of the spherules aligns with other materials found within the Australasian tektite strewn field.

While these specific spherules appear to have a local origin, this does not discount the existence of interstellar meteorites on Earth. The search for such objects continues, as there is a high probability that interstellar material has indeed reached our planet. Future studies and observations will be crucial in furthering our understanding of cosmic interactions with Earth.

Reference: Loeb, A., et al. “Recovery and Classification of Spherules from the Pacific Ocean Site of the CNEOS 2014 January 8 (IM1) Bolide.” Research Notes of the AAS 8.1 (2024): 39.

Reference: Desch, Steve. “Be, La, U-rich spherules as microtektites of terrestrial laterites: What goes up must come down.” arXiv preprint arXiv:2403.05161 (2024).