Violent impacts from comets and other hurtling bodies can pepper planets and their moons with the molecular building blocks of life, new research suggests.
The high-speed collisions unleash intense shock waves that can turn simple organic compounds found in comets and on icy worlds into amino acids, which make proteins, cells and ultimately all living organisms.
The findings suggest that rather than being a purely destructive force, the impacts increase the chances of life originating and being widespread across our solar system.
“We know that impacts are very common in the solar system, because we can see the craters left behind on different planetary bodies,” Imperial College London astrobiologist Zita Martins said. “If impacts occur, then more complex molecules can be made, so these building blocks of life could be widespread throughout our solar system.”
Scientists have previously used computer models to demonstrate that shock waves could turn simple molecules found in icy comets, such as ammonia, carbon dioxide and methanol, into complex amino acids. That work prompted researchers to test the idea by reconstructing celestial impacts in the laboratory.
Researchers at Imperial College and the University of Kent teamed up with Nir Goldman, a researcher at the US Lawrence Livermore National Laboratory, whose models showed amino acids might be made in comet strikes. They made batches of ice mixture laced with ammonia, methanol and carbon dioxide to represent different compositions of comets.
Writing in the journal Nature Geoscience, the researchers show that an impact at about 7km per second produced scores of amino acids in one ice mixture. The impact creates an intense shock wave that fragments the simple compounds, which then recombine into amino acids, such as alanine and glycine. Among the roles they play in life, glycine is a neurotransmitter, which is active in the brain stem and retina, while alanine is found in bacterial cell walls.
“Although there are other chemical paths that can generate amino acids, the one we describe can occur during an impact, where no special conditions, such as UV radiation, are required, if the initial ingredients are present,” said Mark Price, co-author of the study at the University of Kent. “The important implication is that the complex precursors to life, such as amino acids, are widespread, thus increasing the chances of life evolving elsewhere.”