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Cambridge study challenges comets’ role in life’s origins

Computer modelling suggests fragile prebiotic molecules would rarely survive comet impacts on early Earth.

A peer-reviewed study led by researchers at the University of Cambridge has challenged the idea that comets regularly delivered the chemical ingredients for life on Earth. The authors say cometary delivery remains possible but would have been extremely rare.

The research, published in Scientific Reports, examined whether hydrogen cyanide and other organic molecules carried by comets could survive passage through Earth’s atmosphere and impact with the surface. The researchers combined models of comet dynamics, atmospheric entry and impact conditions.

Their simulations suggest that comets usually travelled too fast or entered at angles that would have destroyed or vaporised fragile molecules. Even in cases where molecules survived, the concentration delivered to the surface would probably have been too low for useful prebiotic chemistry.

The researchers describe the scenario as a possible one-off event rather than a dependable supply mechanism. That does not show that comets played no role in Earth’s history, and it does not identify a replacement explanation for the origin of life.

The study also suggests that Mars may have offered slightly better conditions for cometary delivery because its thinner atmosphere would have made it easier for material to reach the surface. The authors stress that this is a modelling result, not evidence that life or its chemical precursors arrived on Mars.

The work is a new analysis of a long-standing hypothesis, not a final answer about how life began. Other possibilities include chemical processes on Earth or delivery by asteroids, and the relative importance of those routes remains unresolved.

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