Study finds comets unlikely to have delivered life's building blocks to Earth

By the Everything Space news desk · 28 Oct 2026 · written from the sources below

Image: Phys.org

New simulations suggest fragile prebiotic molecules carried by comets would mostly vaporize on impact, undercutting a popular origin-of-life theory.

A new study led by researchers at the University of Cambridge casts doubt on the idea that comets seeded Earth with the molecular ingredients for life. Using computer modeling, the team found that any successful delivery of organic molecules by comets would have been an extreme rarity rather than a consistent source of prebiotic material.

The researchers modeled the speed and angle at which comets would strike Earth's atmosphere and found that these impacts were generally too fast and too steep for delicate organic molecules to survive. Instead, such molecules would likely vaporize before ever reaching the surface.

The team focused on hydrogen cyanide, a molecule commonly found in comets and considered important for prebiotic chemistry. Even in rare cases where it might survive impact, the simulations showed that the odds of achieving a concentration useful for kickstarting life's chemistry were vanishingly small, especially given how quickly comet strikes declined during Earth's first half billion years.

Interestingly, the study found that Mars might have been a somewhat more favorable target for this kind of delivery, since its smaller size and thinner atmosphere could have let more cometary material reach the ground intact during the solar system's early, comet-heavy period. The researchers stress this doesn't confirm it happened on Mars, but it suggests that if it was unlikely on Earth, it may have been just as unlikely-or more likely-there.

With comets looking like an improbable source, the researchers point to other explanations for life's chemical origins, such as asteroid impacts, which occurred far more frequently, or chemical processes that unfolded entirely on Earth without outside input.

The team suggests their findings could help guide the search for life beyond our solar system, particularly as next-generation telescopes come online, by helping identify which planetary systems might realistically support this kind of prebiotic delivery mechanism.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.