Comets probably didn't seed life on Earth after all

Full narration (transcript)

Comets probably didn't seed life on Earth after all. A University of Cambridge team modelled how comets deliver fragile prebiotic molecules, published in Scientific Reports. The romantic idea was that giant space snowballs brought carbon and nitrogen building blocks ready-made. But the models say comets hit too fast, and at too sharp an angle. The fragile organics would almost certainly vaporise. They focused on hydrogen cyanide, or H C N, a key prebiotic molecule often found on comets. Even a useful delivery would be, at best, a one-off fluke — not a steady rain of ingredients. In Earth's first 500 million years there were, at most, a handful of chances for that kind of H C N delivery. More likely sources: asteroid impacts, which were far more common, or chemistry that started on Earth itself. Mars looks a bit less unlikely because it's smaller with a thinner atmosphere — but still highly unlikely. Lead author Richard Anslow says we can't rule it out completely. It just looks vanishingly rare. Follow the link to the main website for much deeper information.

Sources

1. [1] phys.org, 28 Oct 2026 (University of Cambridge). https://phys.org/news/2026-10-comets-didnt-seed-life-earth.html
2. [2] Anslow R et al. Cometary delivery of prebiotic molecules. Scientific Reports. 2026. doi:10.1038/s41598-026-74214-y. https://doi.org/10.1038/s41598-026-74214-y