‘Bouncing’ Comets Could Deliver Life’s Building Blocks To Earth And Alien Planets, Study Finds


“Bouncing” comets could have delivered the building blocks for life on Earth and may have seeded other planets with key ingredients as well, according to research published Wednesday in the Proceedings of the Royal Society A, a finding that adds to our understanding of the potential origins of life that could help narrow down places to search for alien life beyond our solar system.

Key Facts

The emergence of life on Earth required a set of chemical precursors like amino acids and proteins that scientists believe developed naturally from a “primordial soup” or arrived when objects like comets and asteroids crashed into the planet from outer space.

While it is still an open question as to how life began on Earth, researchers from the University of Cambridge said their research has identified a mechanism through which comets could potentially deliver these chemical building blocks for life to other planets in the galaxy.

The complex molecules needed to form life would typically be destroyed in the high energy environment created when a comet enters a planet’s atmosphere and strikes a planet but the researchers said the chemicals could survive if the comet was moving slowly enough.

For planets orbiting a star like our own Sun, the researchers said mathematical models show that these slow speed collisions—below 15 kilometers per second—are more likely if multiple planets are clustered together in close orbits.

These “peas in a pod” planets could bounce a comet around like a cosmic pinball with their gravitational pulls and slow it down enough to deliver a payload of intact chemical precursors for life, the researchers said.

First author Richard Anslow, from Cambridge’s Institute of Astronomy, said the “exciting” finding means scientists “can start identifying the type of systems we can use to test different” scenarios for the possible origin of life elsewhere in the universe.

Key Background

Earth is the only place in the universe known to harbor life and despite years of searching, scientists have no clear idea of how life got started, what conditions it requires or whether it exists elsewhere in the universe. Scientists do not even have a unified definition of what life is or whether it would resemble life on Earth. Given the number of planets out there, many are puzzled and even concerned by the stony silence from outer space and our failure to find any signs of intelligent life out there at all, also known as the Fermi Paradox. Our lack of contact is not through lack and experts and space agencies, including NASA, have been hunting for signs of life and attempting to detect radio transmissions from other planetary systems.

Crucial Quote

“In these tightly-packed systems, each planet has a chance to interact with and trap a comet,” said Anslow, adding that “it’s possible that this mechanism could be how prebiotic molecules end up on planets” instead of being formed through chemical reactions on the planet. “It’s a different way to look at the great work that’s already been done on Earth,” he said. “What molecular pathways led to the enormous variety of life we see around us? Are there other planets where the same pathways exist? It’s an exciting time, being able to combine advances in astronomy and chemistry to study some of the most fundamental questions of all.”

Further Reading

A New Theory on Why We Haven’t Found Aliens Yet: They’re sleeping. (Slate)

Scientific AmericanThe Search for Extraterrestrial Life as We Don’t Know It
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