Life’s first handshake.
Take a look at your hands — they are mirror images of each other. Just like your hands, certain organic molecules have mirror images of themselves, and this is a chemical property known as chirality. But some of these ‘handed’ molecules that are key for biological life, such as amino acids, proteins, enzymes, and sugars, are found in nature as only left-handed or right-handed. This is a phenomenon known as homochirality.
Although homochirality molecules have been found in meteorites and comets in our solar system, none have been detected outside of the Milky Way. Until now, that is.
Using the Green Bank Telescope (GBT) in West Virginia and observations from CSIRO’s Parkes radio telescope in Australia, scientists discovered the molecular signature of propylene oxide (CH3CHOCH2) in an interstellar gas cloud about 3 million times the mass of our sun, called Sagittarius B2, located about 390 light-years from the centre of the Milky Way.
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"This is the first molecule detected in interstellar space that has the property of chirality, making it a pioneering leap forward in our understanding of how prebiotic molecules are made in the Universe and the effects they may have on the origins of life," said Brett McGuire from the National Radio Astronomy Observatory in Virginia and first author of the study, in an NRAO news release.
But no one knows how homochirality came about, so the discovery of a handed molecule in Sagittarius B2 is a pretty big deal.
"Propylene oxide is among the most complex and structurally intricate molecules detected so far in space," said second author, Brandon Carroll, from the California Institute of Technology in Pasadena. "Detecting this molecule opens the door for further experiments determining how and where molecular handedness emerges, and why one form may be slightly more abundant than the other."
How did this organic molecule originate? Researchers think it likely formed in the gas cloud due to thin mantles of ice developing on extremely tiny dust grains floating in space. What’s more, these chiral molecules might eventually make their way onto asteroids and comets, which could end up on the surface of planets after an impact.
"Meteorites in our Solar System contain chiral molecules that predate Earth itself, and chiral molecules have recently been discovered in comets," said Carroll. "Such small bodies may be what pushed life to the handedness we see today."
Next, the scientists will determine whether the detected propylene oxide molecules are left-, or right-handed. The study is published in the journal Science.
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