Fischer-Gödde and colleagues used ruthenium isotopes in 2024 to show the Chicxulub impactor was a carbonaceous-type asteroid formed beyond Jupiter's orbit, ruling out a comet and noting that five other impacts they tested were ordinary inner-belt rocks. In July 2026, Makhatadze and colleagues measured nickel isotopes in marine clays holding the impact ejecta and constrained the impactor to CO chondrites and some ungrouped chondrites.
Coverage declared the asteroid finally identified. The paper's own language is most likely CO chondrite-like, with ungrouped chondrites still inside the constraint: the clan named, not the parent body. Per the Vrije Universiteit Brussel release, carbonaceous chondrites are about five percent of meteorites found on Earth, and CO types are a small fraction of those.
The identification rests on isotope ratios in ancient clay: a nickel atom's weight, measured sixty-six million years after the fact, discriminates between rock families born in different suburbs of the young solar system. The chain from that measurement to a dinosaurless world is itself the artifact.
If the rarest rocks do the most damage, what exactly is the sky survey protecting us from?