Science & Tech · Science & Environment · 13 hrs ago
Comets were unlikely to deliver life's building blocks to early Earth
Researchers say comets probably did not deliver life's building blocks to Earth because most would have struck too fast and at too steep an angle.
Comets contain organic compounds, including hydrogen cyanide, which can help drive chemical reactions linked to life.
Scientists have proposed that comets supplied some of the chemistry needed for life to begin during Earth's early history.
A team led by Richard Anslow used computer simulations to test whether hydrogen cyanide could survive a comet's passage through the atmosphere and its impact.
The simulations found that intact delivery would be extremely rare; the study estimates only one impact over more than a billion years might deliver a meaningful amount.
Any surviving material would also need to land on solid ground, since the ocean could dilute it too quickly.
The findings challenge the idea that comets seeded Earth with life's chemical ingredients, but do not rule it out completely.
A new study says comet impacts were unlikely to deliver enough intact organic molecules to early Earth to help life begin.
Researchers used computer simulations focused on hydrogen cyanide, a molecule that can drive chemical reactions relevant to life.
Most comets would have struck Earth too fast and at too steep an angle for the molecules to survive.
The study, published in Scientific Reports, does not rule out comet delivery but finds that successful impacts would have been rare.
The researchers say asteroids or chemical processes on Earth itself could be alternative sources of life’s building blocks.
- Who
- Researchers led by Richard Anslow, including a team from the University of Cambridge.
- What
- A study found that comets were unlikely to deliver enough intact organic molecules to early Earth to help life begin.
- When
- Published October 28, 2026.
- Where
- The study concerns comet impacts on early Earth and was published in Scientific Reports.
- Why
- Most comets would have struck too fast and at too steep an angle for molecules such as hydrogen cyanide to survive in useful amounts.
Proponents of comet delivery
Researchers skeptical of comet delivery
Likelihood
Proponents of comet delivery
Comets carry organic compounds and may have supplied early Earth with chemical building blocks for life.
Researchers skeptical of comet delivery
Simulations suggest successful delivery of useful amounts of hydrogen cyanide would have been extremely rare.
Evidence
Proponents of comet delivery
Rosetta detected glycine and phosphorus on comet 67P/Churyumov–Gerasimenko.
Researchers skeptical of comet delivery
High impact speeds and steep angles would destroy most organic compounds, the researchers say.
ESA’s Rosetta mission visited comet 67P/Churyumov–Gerasimenko and detected glycine and phosphorus.
Anslow and colleagues proposed that comets could be slowed by bouncing between planets in systems with closely spaced planets.
The study on comet impacts and the origins of life was published in Scientific Reports.
- Study journal
- Scientific Reports
- Molecule studied
- Hydrogen cyanide (HCN)
- Comet visited by Rosetta
- 67P/Churyumov–Gerasimenko
- Rosetta visit
- 2014
- Study lead author
- Richard Anslow
3 sources
What people are saying
It’s kind of a romantic idea, but our results suggest it’s highly unlikely.
Even though we see that comets contain all of these molecules in really high concentrations, it’s not straightforward to go from there to saying we’re going to have all of these available for prebiotic chemistry on the surface of the Earth
But it’s important to revisit these ideas as our understanding of both comets and the early solar system improves