NASA astrobiologists have
discovered amino acids -- a core building block of life -- in a type of meteorite previously thought unable to harbour such complex organic molecules. Its surprise discovery has caused the agency to rethink basic assumptions of how the acids are formed.
Amino acids are like the Lego bricks of life, a fundamental component that underpins every living thing on Earth. 20 different amino acids are used, in an enormous variety of arrangements, to build the millions of different proteins that all Earthly life is built upon.
A team led by Dr Daniel Glavin of NASA's Goddard Space Flight Centre discovered the acids in a Ureilite
meteorite: a rare type of celestial object created when two asteroids collide. The shock of that impact heats the meteorite up to enormous temperatures of almost 1,100 degrees Celsius, a blisteringly hot temperature that would turn any organic molecules, including amino acids, into fried carbon.
But the fragile compounds were still found on the unceremoniously named
Asteroid 2008 TC3 when it crashed into the Nubian Desert of northern Sudan back in 2008. And seeing as Earth only uses left-handed amino acids, and the 19 different acids sampled were both left- and right-handed, they had to have come from space rather than Ureilite being contaminated by Earth.
So how did the amino acids end up on a Ureilite, which would have subjected to temperatures hot enough to melt iron, and quickly turn the organic building blocks into
carbon? Glavin thinks they were created after the initial impact, even though there would be no water to help form the amino acids.
It suggests that there are other ways that these acids are created, outside of the water-based mechanisms that biologists recognise. "Finding them in this type of meteorite suggests that there is more than one way to make amino acids in space," said Dr Glavin, "which increases the chance for finding life elsewhere in the
universe."
Now, the team at Goddard is planning experiments to test various gas-phase chemical reactions, to see if they too generate amino acids without
water, and prove the hypothesis.
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