A special property of Earth's organic molecules could be caused by supernovae, a new study says — suggesting that life’s building blocks were created not on Earth, but elsewhere in the cosmos.
Many of these building blocks, such as amino acids, sugars and other molecules, are chiral — they come in two identical forms that are mirror opposites. Human hands are the best example of chirality: They are asymmetrical mirror images of each other, so you cannot superimpose them on each other. Imagine using your left hand to shake someone's right hand.
In chemistry, chirality refers to asymmetrical molecules that also cannot be superimposed on each other. They are considered right- or left-handed depending on how their atoms are arranged.
On Earth, life tends to be left-handed (though a recent study suggests its lower forms can be ambidextrous). Left-handedness also seems to prevail throughout the cosmos, according to studies of meteorites. Researchers from Lawrence Livermore National Laboratory believe supernovas are the reason.When a star collapses, it ejects a slew of particles that include electron antineutrinos, which are right-handed. Nuclear astrophysicist Richard Boyd and his colleagues suggest these particles would interact with right-handed nitrogen atoms inside amino acid molecules.
This interaction would convert the nitrogen into carbon, thereby destroying the righty amino acid molecules. The left-handed nitrogen would be left alone, for the most part, which means left-handed amino acids would be dominant. That could explain their prevalence on Earth and elsewhere in the universe.
Boyd says it might be possible to run experiments using intense neutrino sources, such as the Spallation Neutron Source at Oak Ridge National Laboratory, to test this theory.
If it’s true, it could mean that Earth’s amino acids did not arise on Earth, but elsewhere in the universe. We are all star stuff, indeed.
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