Some of the key ingredients for life may have been shocked into existence. A physical simulation of a comet鈥檚 impact with a planet shows that the conditions are extreme enough to create amino acids within the comet鈥檚 ice.
Astrobiologists have long wondered whether life or its ingredients could have travelled to Earth on the back of a comet or asteroid. Comets are known to contain the organic precursors of amino acids, which are the building blocks of proteins.
What鈥檚 more, one comet, Wild 2, was recently shown to contain the simplest amino acid, glycine. But how such an amino acid could form there is still a mystery.
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鈥淲e do, however, know that high speed impacts are a ubiquitous process as we see impact craters on every solid surface in the solar system,鈥� says at the University of Kent, UK.
Speeding pellet
Theoretical studies had suggested that the shock of an impact could rearrange the components of the ice into something more interesting.
鈥淭he idea is that a comet would contain the raw materials for life-building compounds,鈥� says of Lawrence Livermore National Laboratory in California, who made the theoretical calculations. 鈥淲hen a comet impacts a planetary surface, it creates very high pressures and temperatures. Those will then drive the raw materials that already exist in the comet to form more complex things that could be life-building.鈥�
To find out if this works in practice, Price and colleagues made model comet ice in the lab containing various amounts of ammonia, carbon dioxide and methanol. Then they shot the ice with a steel pellet travelling at about 7 kilometres a second to simulate the comet smacking into a planet, or another body colliding with the comet.
The goop that remained after the ice was evaporated away was analysed by Price鈥檚 colleague , who found it contained the amino acids alanine and norvaline.
鈥淭his is significant, as we now have a simple, realistic mechanism to generate amino acids,鈥� Price says. 鈥淎s impacts between icy bodies occur throughout the solar system, then complex organic molecules are also, very probably, widespread.鈥�
鈥淭his is a neat way of suggesting prebiotic material could be produced regardless of the external conditions of the planet,鈥� says Goldman.
鈥淵ou could have a planet that isn鈥檛 really conducive to forming amino acids, like early Earth supposedly wasn鈥檛,鈥� he says. 鈥淏ut then you can have a comet come in, and that impact will drive prebiotic processes within the comet itself, regardless of what the planet looks like.鈥�
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