Solving a Three-dimensional Jigsaw: A Key to Life Before Its Origin on Earth?

Flip a coin. You'll get heads or tails. Flip a thousand coins and you'd expect roughly half of each. The odds of flipping every single one and getting a head are incredible - which makes it all the more mysterious that life seems to come from an even greater coincidence. Arizona State and Brown University researchers have shown that these unlikely odds may have come from space - which answers one question by asking ten far bigger and cooler ones.

Many organic molecules have a "handedness" - just like your hands, amazingly enough, two versions of the same thing identical in all respects except being mirror images. See, not all the molecular chemistry is hard! When these chemicals are created in the laboratory they show the even-handed 50/50 split you'd expect - but all life on Earth is based on the fact that our amino acids are all lefties, while the DNA molecules are right handed. Why this should be has been a chemical question for a long time.

In 2004, Professor Pizzarello and colleagues showed that this life-question could predate life itself. While evolving complex species over millions of years might seem like a huge and incredible process (so huge that some people refuse to believe it happened at all), it was preceded by an infinitely vaster chemical puzzle. Lakes of acid-this and molecular-that before even the simplest bacteria, acting and reacting on each other, eventually giving rise to the precursors of life. Imagine doing a three-dimensional jigsaw with a million parts by putting all the pieces in a box and shaking- it took a long time. Professor Pizzarello's research showed that a few asymmetric amino acids in this soup could catalyse certain reactions, tipping the entire chemical balance in favor of one-handednesses.

A demonstration which has just become a lot more exciting with the detection of those asymmetric acids in meteorite fragments. Up until now meteors have always shown the same handedness as terrestrial life, because by the time we get to them they've been covered in the stuff. Fortunately meteorite GRA95229 (snappy name) smashed into the Earth and was immediately stored in the ultimate safe deposit box: beneath a huge glacier where nothing could affect it. Recently excavated, space center facilities were employed to keep it free from contamination until we could learn what we needed - that asymmetric chemicals exist beyond the Earth.

This doesn't explain why all the life on Earth is one-handed - it does the other science thing instead, upgrading the question to far better and more mysterious ones. How far throughout the universe are these chemicals one-sided - and why? Was all life on Earth injected by a bunch of lop-sided chemicals hitch-hiking on a meteorite impact? And if life on Earth came from space - can we really doubt that it's out there too?

Posted by Luke McKinney.