Comet Impacts May Have Jump-Started Life on Earth

An image of Halley's Comet taken in 1986.
An image of Halley's Comet taken in 1986. (Image credit: NASA)

Life's building blocks can form in the harsh environment of deep space, a new study suggests, bolstering the odds that a comet or meteorite strike may have jump-started biological evolution on Earth.

Linked pairs of amino acids called dipeptides can take shape in space-like conditions, a team of chemists found. Dipeptides brought to Earth aboard a comet or meteorite billions of years ago may have then catalyzed the formation of even more complex molecules necessary for life as we know it, such as proteins and sugars, researchers said.

"It is fascinating to consider that the most basic biochemical building blocks that led to life on Earth may well have had an extraterrestrial origin," study co-author Richard Mathies, of the University of California, Berkeley, said in a statement.

The chemists created a mock mini-comet in the lab, chilling a mixture of carbon dioxide, ammonia and various hydrocarbons such as methane and ethane down to 10 degrees above absolute zero (minus 442 degrees Fahrenheit, or minus 263 degrees Celsius) in a vacuum chamber.

They then zapped the mixture with high-energy electrons, simulating the effect of impacts by cosmic rays — fast-moving charged particles that pervade our Milky Way galaxy.

The electrons sparked some interesting reactions. The team detected many complex, carbon-containing organic molecules, including nine different amino acids and at least two dipeptides.

The new study, which was published online last week in The Astrophysical Journal, breaks ground by showing that molecules as complex as dipeptides can probably form far from Earth. But it also adds to a growing body of evidence indicating that organics may be common throughout the solar system.

Amino acids have been found in comets and meteorites, and organics swirl about in the thick, nitrogen-based atmosphere of Saturn's huge moon Titan. Many researchers think organics are also common on the dwarf planet Pluto and other objects in the Kuiper Belt, the ring of icy bodies beyond Neptune's orbit.

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Mike Wall
Senior Space Writer

Michael Wall is a Senior Space Writer with and joined the team in 2010. He primarily covers exoplanets, spaceflight and military space, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.