{"id":804174,"date":"2026-11-01T08:58:32","date_gmt":"2026-11-01T13:58:32","guid":{"rendered":"https:\/\/spaceweekly.com\/?p=804174"},"modified":"2026-11-01T08:58:32","modified_gmt":"2026-11-01T13:58:32","slug":"did-comets-seed-life-on-earth-a-new-study-says-probably-not","status":"publish","type":"post","link":"https:\/\/spaceweekly.com\/?p=804174","title":{"rendered":"Did comets seed life on Earth? A new study says \u2014 probably not"},"content":{"rendered":"
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\nView larger. | Did comets seed life on Earth? That\u2019s been the leading theory for the past 100 years. But a new study suggests it was unlikely. Image via N. Lira\/ ALMA\/ ESO\/ NAOJ\/ NRAO.<\/figcaption><\/figure>\n<\/div>\n
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For about the past century,<\/strong> scientists have believed that comets brought the seeds of life \u2014 prebiotic molecules \u2014 to Earth. But is it true? Did comets seed life on Earth?<\/li>\n
A new study says \u2014 probably not. <\/strong>The study suggests that scenario \u2014 planetary life seeded by comets \u2014 was rare in our solar system.<\/li>\n
Any molecules delivered to Earth<\/strong> were likely deposited in a one-off event, the study says, not on an ongoing basis.<\/li>\n<\/ul>\n
Science news, night sky events and beautiful photos, all in one place.<\/em> Click here to subscribe to our free daily newsletter.<\/strong><\/p>\n
Did comets seed life on Earth billions of years ago?<\/h3>\n
For the past century, scientists have believed that comets likely brought the chemical and molecular building blocks of life to Earth. But did they? A new study challenges that long-standing theory.<\/p>\n
Researchers from the University of Cambridge in the U.K. led the new study. They said on October 28, 2026, that any material that comets did deliver was probably a one-off fluke. That\u2019s in contrast to the idea of a steady supply of life-seeding molecules from comets, raining down from the skies.<\/p>\n
And it means comets bringing these molecules to Earth was likely an exceedingly rare event, the scientists say.<\/p>\n
The researchers published their potentially game-changing peer-reviewed results in Scientific Reports<\/em> on October 28, 2026.<\/p>\n\n
Organic molecules wouldn\u2019t survive<\/h3>\n
The main problem with the life-seeded-by-comets theory has to do with the comets themselves. They move too fast.<\/p>\n
The researchers created a computer model \u2014 a digital representation of a real-world system \u2014 to learn that comets would approach Earth too fast and at too sharp an angle to be effective life-seeders.<\/p>\n
They learned that the organic molecules in comets are fragile. If these molecules did manage to make the fiery journey through Earth\u2019s atmosphere \u2014 and reach Earth\u2019s surface \u2014 they\u2019d likely have vaporized on impact, according to this research. It\u2019s possible the organic molecules from comets might survive an impact on Mars, with its weaker gravity. But even that is unlikely, the researchers say. Richard Anslow at the University of Cambridge\u2019s Institute of Astronomy is the lead author of the new study. Anslow said:<\/p>\n
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This is not to say it definitely happened on Mars, of course. But suggests it would be unlikely if it happened on Earth and didn\u2019t happen on Mars. <\/p>\n<\/blockquote>\n
Or the other, perhaps more likely, alternative is that it didn\u2019t happen on either planet. Anslow said:<\/p>\n
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Historically, scientists thought that comets were important for the origin of life on Earth, because they carried carbon- and nitrogen-bearing molecules, so these giant space snowballs were almost like a \u2018get out of jail free card\u2019 that brought all the molecules a planet would need to seed life. It\u2019s kind of a romantic idea, but our results suggest it\u2019s highly unlikely.<\/p>\n<\/blockquote>\n
Could comets slow down enough?<\/h3>\n
There was another scenario that the researchers had considered. If planets in a planetary system were orbiting close enough together, that might cause comets to slow down. Basically, the comets would \u201cbounce\u201d from one planet to the next, as previously reported by EarthSky in 2023. And they would deliver the organic molecules as they did so.<\/p>\n
But could that have happened in our own solar system? The researchers investigated the possibility. They used recent advances in comet impact simulations, comet-atmosphere interactions and dynamic modeling of the origin and evolution of comets. As Anslow noted:<\/p>\n
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We\u2019re learning more and more all the time about how our solar system and the Earth formed, and pulling this together with lots of different advances in modelling, which allowed us to investigate this idea that has been around for close to a century,<\/p>\n<\/blockquote>\n
But, these scientists said, even that scenario would be rare. Even if the molecules survived hitting the surface of a planet, there wouldn\u2019t be enough of them to help kickstart life. They said that\u2019s true even for hydrogen cyanide (HCN), one of the most important life-related molecules found in comets in our solar system.<\/p>\n
\nArtist\u2019s concept of comets orbiting a young star. An earlier study had suggested that in some newly forming planetary systems, comets could \u201cbounce\u201d between the orbits of different planets. That motion could slow down the bouncing comets enough to crash into a planet without destroying the comets\u2019 precious cargo: life\u2019s building blocks. Image via NASA\/ FUSE\/ Lynnette Cook.<\/figcaption><\/figure>\n<\/div>\n
Over time, comets strikes would have declined<\/h3>\n
There\u2019s also the element of time. Our solar system formed about 4.6 billion years ago from a vast, swirling cloud of gas and dust. As the sun took shape at the center, leftover material collided and clumped together, gradually building the planets. <\/p>\n
But the early solar system was a chaotic place, with asteroids, comets and other bits of debris flying about and crashing into the young worlds. Some researchers have proposed that comets delivered organic molecules \u2014 the chemical ingredients for life \u2014 to early Earth. But this scenario would have had to play out early<\/em> in the solar system\u2019s history. <\/p>\n
Scientists believe the rate of comet impacts on Earth dropped considerably after the first 500 million years. And even then, the chances of comets delivering enough of the organic molecules to seed earthly life was slim. Anslow said:<\/p>\n
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It would really have to be a one-in-a-million occurrence, because not only would you need an impact at just the right speed and just the right angle, you would also need everything to happen after that point, in terms of the concentration and the speed at which the chemical origins of life got going. We can\u2019t rule out for certain that it happened that way. But it seems to be a really rare occurrence; at best, a one-off fluke.<\/p>\n<\/blockquote>\n
\nArtist\u2019s concept of Earth and a couple of nearby asteroids. Asteroids could also have potentially brought the seeds of life to Earth. Image via ESA\/ P. Carril.<\/figcaption><\/figure>\n<\/div>\n
Origins of the seeds of life<\/h3>\n
The findings present an important question. If the seeds of life didn\u2019t come from comets, then where did they come from? There are various possibilities.<\/p>\n
It\u2019s possible they came from asteroids rather than comets. Asteroid impacts were a lot more common than comet impacts. And asteroids carry many of the same molecular building blocks.<\/p>\n
Or, the molecules might simply have originated right here on Earth. And so the search for answers about the origin of life on Earth continues.<\/p>\n
Bottom line: Did comets seed life on Earth? It\u2019s unlikely, a new study from the University of Cambridge says. It would have been a very rare occurrence.<\/p>\n
Source: Cometary impacts an unlikely pathway towards the origins of life on Earth<\/p>\n
Via University of Cambridge<\/p>\n
Read more: The best comets of 2026: Here\u2019s what to watch for<\/p>\n
Read more: TESS finds 30 exocomets for Beta Pictoris<\/p>\n
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Paul Scott Anderson<\/h4>\n
View Articles\n <\/p><\/div>\n
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About the Author:<\/h6>\n
Paul Scott Anderson has had a passion for space exploration that began when he was a child when he watched Carl Sagan\u2019s Cosmos. He studied English, writing, art and computer\/publication design in high school and college. He later started his blog The Meridiani Journal in 2005, which was later renamed Planetaria. He also later started the blog Fermi Paradoxica, about the search for life elsewhere in the universe.
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\nWhile interested in all aspects of space exploration, his primary passion is planetary science and SETI. In 2011, he started writing about space on a freelance basis with Universe Today. He has also written for SpaceFlight Insider and AmericaSpace and has also been published in The Mars Quarterly. He also did some supplementary writing for the iOS app Exoplanet.
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\nHe has been writing for EarthSky since 2018, and also assists with proofing and social media.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n
![\"Multiple](\"https:\/\/earthsky.org\/upl\/2023\/11\/comets-Beta-Pictoris-artist-concept-August-3-2007.jpg\")
![\"Artwork](\"https:\/\/earthsky.org\/upl\/2024\/06\/2-asteroids-pass-Earth-ESA-P-Carril.jpg\")