Changing Planet

Did Comets Kick-Start Life On Earth?

An artist concept of a young rocky planet being bombarded by comets. Credit: NASA/JPL-Caltech

A thought-provoking new study is bolstering the notion that comets raining down on Earth billions of years ago may have seeded our young planet with the organic building blocks of life.

Through powerful computer simulations of comet impacts of various sizes, astronomers have found that it is possible that complex organic molecules  may have hitched a ride on inbound comets, successfully delivering them to the surface of the Earth. (Related: Did Comets Make Life on Earth Possible?)

Previous research suggests that our planet billions of years ago was without much of a habitable environment except possibly for the ancient oceans where all the ingredients of life may have come together. (See also: Comet Swarm Delivered Earth’s Oceans?)

This new study however suggests that comets might have been key in bringing to Earth the right molecules, like copious amounts of water, carbon dioxide, ammonia and alcohol too.

Researchers estimate that when the Earth was young and was going through periods of ongoing bombardments from comets and asteroids, there may have been as much as 10 trillion kilograms (22 trillion pounds) of organic matter carried to Earth’ surface each and every year!

These impacts would end up,  “delivering up to several orders of magnitude greater mass of organics than what likely pre-existed on the planet,” said co-author Nir Goldman of Lawrence Livermore National Laboratory, California, in a press statement.

The energy of the impact itself would be nature’s driving force that helped spark the synthesis of a soup of prebiotic compounds that would eventually help form  important precursors that would jump-start life- like proteins, enzymes, sugars and even the bases of DNA and RNA.

“Cometary impacts could result in the synthesis of prebiotic molecules without the need for other ‘special’ conditions, such as the presence of catalysts, UV radiation, or special pre-existing conditions on a planet,” said Goldman.

“This data is critical in understanding the role of impact events in the formation of life-building compounds both on early Earth and on other planets and in guiding future experimentation in these areas.”

The research will appear in the June 20 issue of The Journal of Physical Chemistry A.

Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.
  • Syed Mashkur Alam

    These are very old stories about the creation of life-form on Earth. I am very surprised to see the scientists are not any less than any religious fundamentalists. Because, their trend to prove that ‘only we are right’. The only difference between them is that, they don’t throw mortars to prove their theory.

    But, there are books already prevailing amongst us about the creation of the Universe, in the name of Old Testament, New Testament and Qur’an. If anybody is skeptical about Qur’an, read Genesis and Exodus. Please don’t call them mere stories or imaginary theories. If you call deny them, how can you expect them to accept your theories..? Because, whatever is written about the creation of life-form is still remaining as a concept only. There is no solid evidence. Perhaps God could have made it easy for you with the detailed explanations, but He didn’t. Because it was not His objective to explain His scientific formulas. Rather He intended human being to believe in what He has done and follow the paths of the chosen ones throughout the entire human history.

    Still you have a chance to improve in your researches, only if you can follow His books. Please don’t ignore this suggestion. This will help you to quench your thirst of knowledge for sure.

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (

Social Media