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Icy Comet Collisions 'Can Spawn Life'
The building blocks of life can spontaneously come into existence when icy comets smash into planets, according to a new study.
A similar process can create amino acids when a rocky meteorite strikes an ice-covered planet.
Scientists say the discovery suggests that "the basic building blocks of life can be assembled anywhere in the Solar System".
How often the building blocks end up constructing proteins and living organisms is an unanswered question.
But the research fills in another piece of the puzzle of life's origins on Earth.
Scientists believe that about the time life first emerged, between 4.5 and 3.8 billion years ago, Earth was being bombarded by comets and meteorites.
Dr Zita Martins, from the Department of Earth Science and Engineering at Imperial College London, said: "Our work shows that the basic building blocks of life can be assembled anywhere in the Solar System and perhaps beyond.
"However, the catch is that these building blocks need the right conditions in order for life to flourish.
"Excitingly, our study widens the scope for where these important ingredients may be formed in the Solar System and adds another piece to the puzzle of how life on our planet took root."
Proteins, the giant molecules that form living tissue, are made from chains of amino acids whose assembly is directed by the genetic code.
Writing in the journal Nature Geoscience, the scientists show how when a comet impacts it creates a shock wave that generates the molecules needed for amino acids.
Heat from the impact then transforms these molecules into the protein building blocks.
The scientists point out that abundant ice on the surfaces of Enceladus and Europa, two moons orbiting Saturn and Jupiter, could provide the perfect conditions for producing amino acids from meteor impacts.
The study involved firing steel projectiles at high velocity into ice mixtures similar to those found in comets.
A large compressed gas gun, housed at the University of Kent, propelled the projectiles at 4.4 miles per second.
High temperatures and pressures from the impacts led to the creation of several amino acids, including the important protein components glycine and alanine. Non-protein amino acids were also generated.