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Radioactive meteorites may have helped create the building blocks of life a few million years after the solar system was formed.

Amino acids are molecules that combine to form proteins, making them essential for life as we know it. They have been found on carbonaceous chondrites, a type of radioactive meteorite, leading some to postulate that the parent bodies that spawned these space rocks may have played a role in the origins of life.

鈥淭he amino acids produced in meteorite parent bodies would be directly delivered to the ancient Earth as meteorites, and may have become building blocks of life,鈥� says at Yokohama National University in Japan.

Exactly how these amino acids could be created in meteorites has remained a mystery, but now Kobukawa and her colleagues have experimentally shown that some could have been synthesised by chemical reactions driven by gamma rays.

The researchers mixed solutions of ammonia, formaldehyde and methanol in water, in proportions similar to those thought to be found on meteorite parent bodies. They then exposed them to gamma rays produced by a sample of cobalt-60, a stand-in for the same rays known to be produced by radioactive isotopes found on meteorites, such as aluminium-26, that are difficult to work with in the lab due to their long half-lives.

The team measured the amino acids produced by this reaction and found there was a similar proportion of them to that discovered in the Murchison meteorite, a 100-kilogram lump of rock that landed in Australia in 1969.

However, at NASA鈥檚 Goddard Space Flight Center in Maryland says it will be a long time before we can definitively point to the reaction pathway that synthesised amino acids billions of years ago.

鈥淵ou can make amino acids out of many different processes and reactions,鈥� he says, 鈥淎nd what they did is just find one more possible mechanism, which is valid, but not the only one.鈥�

Aponte says there are difficulties in ruling out different candidate processes, since we don鈥檛 have a clear understanding of the different temperatures, compounds or levels of water and irradiation that meteorites encounter over their lifetime, and recreating such conditions is often difficult in a laboratory.

鈥淭here鈥檚 still a lot of work to be done to fully understand how all these different mechanisms come into play,鈥� he says.

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