The same amino acids that are here on Earth have also been found in meteorites. “The bottom line is that you have these materials that come from space,” says researcher Steve Macko. He thinks this points to a cosmic origin for life on Earth.
Making the case for our cosmic origin is the fact that all of the meteorite’s amino acids favor the “left-handed” molecular structure, which is also favored by life on Earth, but just why life chose left over right is a mystery. “Essentially all of your protein is made of L-amino acids,” said Macko. “Why is that? We don’t know. The curious thing is that if you go to a meteorite you find a predominance of the same thing.”
However, life is made up of 20 amino acids and only 8 of these have been discovered in meteorites, so what happened to the other 12? Perhaps they were originally on the meteorites but somehow were destroyed or can’t be detected.
Amino acids were first thought to have been created in the early atmosphere of Earth by lightning-like electrical charges in a fog of water, methane and ammonia. When this atmosphere was recreated in the laboratory by Stanley Miller and Harold Urey, they were able to synthesize amino acids. This would mean that life could be isolated on a single planet.
But then scientists discovered what looked like living organisms on a meteorite that fell near Murchison, Australia in 1969. The mix of amino acids found on the meteorite were similar to those produced in the Miller-Urey laboratory experiments, with one important difference?unlike in the lab experiments, the amino acids on the meteorite were left-handed, just like the amino acids on Earth, so scientists theorized that life must have arrived on Earth from outer space. This means that life travels between planets in our solar system and could even travel between solar systems. This could mean that life is made up of the same basic amino acids all over the galaxy, no matter where it takes root.
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