A new computer‑simulation study from the University of Cambridge has cast doubt on the long‑standing hypothesis that comets delivered the organic molecules that sparked life on Earth. The research, published in Scientific Reports, examined the likelihood that cometary impacts could have preserved and delivered intact organic compounds to the early planet. The study, led by Dr. Richard Anslow of the Cambridge Institute of Astronomy, ran 100,000 simulations of comet impacts during the first 100 million years of Earth’s history. In 54 % of the runs, the simulations found no successful delivery of organic molecules. In the remaining cases, only a few molecules survived, and in a small fraction of simulations as many as three molecules were retained. Dr. Anslow explained that the high impact velocities typical of early cometary collisions would have destroyed most organic material. The research focused on hydrogen cyanide (HCN), a key prebiotic precursor found in dozens of comets, including Halley and Hale‑Bopp. Even when HCN survived an impact, the study suggests it would have been rapidly destroyed in the ocean. Other essential prebiotic molecules that contain phosphorus and sulfur are rarely found in comets, further limiting their potential contribution. The authors note that alternative sources of organic material may have been more important. The primordial “soup” of Earth’s early oceans could have synthesized necessary molecules, and slower, more numerous asteroid impacts—such as those from Bennu and Ryugu—could have delivered a richer supply of amino acids. The study also points out that the early Mars, with its smaller size and greater distance from the Sun, would have experienced lower‑velocity impacts, potentially making it a more favorable environment for cometary delivery. External experts offered cautious commentary. Dr. Queenie Chan of Royal Holloway University of London noted that HCN might have reacted into less stable compounds before entering the ocean, so the results do not entirely rule out cometary contributions. Dr. Nicolle Zellner of Albion College in Michigan said she was not surprised by the findings and that the authors had set realistic parameters for the simulations. The panspermia hypothesis, which proposes that life’s building blocks were seeded on Earth by comets, has been discussed since 1908 and was popularized in 1961. This new study suggests that cometary impacts may have played a smaller role than previously thought, though it does not eliminate the possibility entirely.