Chirality. Are you right- or left-handed?
And did you know that some building blocks of life have an answer to that question, too?
Amino acids are molecules that make up proteins.
All living things on Earth rely on them.
Many amino acids come in two mirror image versions that can't be superimposed.
To get a sense of this,
put your hands palms down and then try to cover one with the other.
See how your thumbs still point in opposite directions?
This handedness is chirality, and it can be found in molecules too.
So who cares if amino acids are north or south paws?
Well, it affects how they interact with life. On Earth,
life produces almost exclusively left-handed amino acids and right-
handed sugars.
But no one knows when or how that convention got started.
One theory is that the solar system predominantly made left-handed
amino acids before life began, and life just followed suit.
To find out, we recently sent a spacecraft called OSIRIS-REx to an asteroid called
Bennu to collect samples of early solar system material and bring them to Earth.
Astrobiologists found amino acids in the rocks from Bennu,
but they weren't all left-handed.
They were evenly split, about half left-handed and half-right.
This suggests that early Earth might have had a more equal mixture of left- and right-
handed amino acids, too, and something about life turned things to the left.
Scientists are just beginning to study
the Bennu samples and are already asking new questions.
Sometimes getting the right data means you're left with an even bigger mystery.