A University of Cambridge team led by Dr. Richard Anslow of the Institute of Astronomy has published a paper in Scientific Reports, dated October 28, 2026, titled "Cometary Impacts an Unlikely Pathway Towards the Origins of Life on Earth."

For roughly a century, scientists have considered comets a likely delivery vehicle for the carbon- and nitrogen-bearing molecules needed for prebiotic chemistry.

The new work argues the delivery would have been, in Anslow's words, "a one-off fluke" at best — a striking reversal of a long-standing assumption about how life's ingredients arrived here.

The researchers used computer models of comet arrivals through planetary atmospheres and found the journey far more hostile than earlier work recognized.

Organic molecules such as hydrogen cyanide — a common comet compound central to proposed pathways toward sugars, lipids, and genetic material — rarely survived impact, according to the srpske.rs report on the paper.

Comets strike too fast and too steeply, and Earth's atmosphere destroys small or obliquely arriving comets first. Even when some molecule did survive, crater-lake groundwater would quickly dilute the concentration below what prebiotic chemistry requires.

According to srpske.rs, in 100,000 simulated bombardment histories of Earth, 54 percent contained no impact that would deliver hydrogen cyanide in sufficient concentration for prebiotic chemistry.

The team also revisited its own 2023 "ping-pong comet" idea — that comets could bounce between nearby planets, shedding organics at gentler speeds — and concluded the scenario is possible but highly unlikely.

Anslow told press it would take a one-in-a-million alignment of impact speed, angle, concentration, and chemistry timing, and that it cannot be ruled out for certain but appears exceedingly rare.

The simulations extended to Venus and Mars, where the researchers found more favorable conditions: Mars's weaker gravity and thinner atmosphere let comets survive impacts far more often — Universe Today-style coverage cited by srpske.rs reports five times more often than on Earth — though the authors still call it a stretch for organics to arrive intact there.

As likelier sources of life's building blocks on Earth, the paper names asteroid impacts, which were far more numerous, and chemical precursors forming on Earth itself without any outside input.

The paper is a modeling estimate, not an observation, and its authors caution delivery cannot be ruled out entirely — only that it is highly unlikely. It also covers just hydrogen cyanide and short-period comets, leaving other compounds untested.

The team suggests future exoplanet searches, including successors to the James Webb Space Telescope such as the proposed Habitable Worlds Observatory, could flag planetary systems where comet-borne delivery is more plausible.

Separately, research in Nature Geoscience covered by Universe Today argues Earth's water may have formed locally from molten pebble rain in a hydrogen-rich early atmosphere, further easing reliance on cosmic deliveries.