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newscientist 00429.txt

#Crack a comet to spawn the ingredients of life Some of the key ingredients for life may have been shocked into existence. A physical simulation of a comet's impact with a planet shows that the conditions are extreme enough to create amino acids within the comet's ice. Astrobiologists have wondered long 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's more one comet Wild 2 was shown recently to contain the simplest amino acid glycine. But how such an amino acid could form there is still a mystery. We do however know that high speed impacts are a ubiquitous process as we see impact craters on every solid surface in the solar system says Mark Price at the University of Kent UK. Theoretical studies had suggested that the shock of an impact could rearrange the components of the ice into something more interesting. The idea is that a comet would contain the raw materials for life-building compounds says Nir Goldman of Lawrence Livermore National Laboratory in California who made the theoretical calculations. When 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. 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's colleague Zita Martins at Imperial College London who found it contained the amino acids alanine and norvaline. This is significant as we now have a simple realistic mechanism to generate amino acids Price says. As impacts between icy bodies occur throughout the solar system then complex organic molecules are also very probably widespread. This is a neat way of suggesting prebiotic material could be produced regardless of the external conditions of the planet says Goldman. You could have a planet that isn't really conducive to forming amino acids like early Earth supposedly wasn't he says. But 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. Journal reference: Nature Geoscience DOI: 10.1038/ngeo1930correction: When this article was published first on 15 september it did not give details of the researcher who detected amino acids in the ice. These have now been included d

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