Overview
- The Cambridge-led paper published Oct. 28, 2026 used new dynamical, atmospheric-entry and impact models to test whether comets could deliver intact hydrogen cyanide to early Earth.
- The team found most comets hit at speeds and steep angles that would vaporize fragile organics so delivery of useful concentrations was extraordinarily rare.
- Across 100,000 simulated comet histories the authors report that meaningful HCN delivery to Earth would be at best a one-in-a-million or one-off fluke.
- The models show Mars’s thinner atmosphere and lower gravity made it somewhat more likely than Earth to preserve cometary organics, changing where astrobiologists might look.
- Authors say the result does not rule out comet delivery but shifts emphasis to carbonaceous asteroids, volcanic or hydrothermal chemistry on Earth, and follow-up modeling and lab tests to reproduce the findings.