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Chirality. Are you
right- or left-handed?

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And did you know that some building blocks of life have an answer to that question, too?

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Amino acids are molecules
that make up proteins.

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All living things on
Earth rely on them.

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Many amino acids come in 
two mirror image versions 
that can't be superimposed.

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To get a sense of this,

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put your hands palms
down and then try to
cover one with the other.

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See how your thumbs still
point in opposite directions?

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This handedness is chirality, and it can be found in molecules too.

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So who cares if amino acids are north or south paws?

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Well, it affects how 
they interact with
life. On Earth,

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life produces almost exclusively left-handed amino acids and right-

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handed sugars.

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But no one knows when or how that convention got started.

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One theory is that the
solar system predominantly
made left-handed

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amino acids before life
began, and life just followed suit.

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To find out, we recently sent a spacecraft 
called OSIRIS-REx to
an asteroid called

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Bennu to collect samples of
early solar system material
and bring them to Earth.

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Astrobiologists found
amino acids in the
rocks from Bennu,

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but they weren't 
all left-handed.

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They were evenly split, about half left-handed
and half-right.

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This suggests that early Earth might have had
a more equal mixture
of left- and right-

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handed amino acids, too, and something about life turned things to the left.

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Scientists are just
beginning to study

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the Bennu samples and are already asking new questions.

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Sometimes getting the right
data means you're left with
an even bigger mystery.