Researchers find first example of chirality in interstellar space

Some organic molecules have “left-handed” and “right-handed” versions, a chemical property referred to as chirality. These mirror-image molecules are crucial for biology and have been discovered in meteorites that have crashed to Earth, as well as comets in our solar system.

In a new study published by the journal Science, researchers describe the first-ever incidence of chirality found in interstellar space.

Using powerful radio telescopes, the study team found propylene oxide near the center of the Milky Way in a massive star-forming cloud of dust and gas called Sagittarius B2 (Sgr B2).

“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,” Brett McGuire, a postdoctoral Fellow with the National Radio Astronomy Observatory (NRAO), told redOrbit in a statement.

Development of organic molecules

Intricate natural and organic molecules develop in interstellar clouds like Sgr B2 in multiple ways. The most basic pathway is through gas-phase chemistry, involving particles merging to generate ever more intricate molecules. To molecules like propylene oxide, thin mantles of ice on dust grains help connect small molecules into bigger structures, astronomers have said. These molecules are able to then evaporate off the grains and react inside the cloud.

Each molecule, as it naturally falls and vibrates in interstellar space, emits a unique signature, a number of identifying spikes that show up in the radio spectrum. Bigger and more intricate molecules have a more intricate corresponding signature, which makes them harder to recognize.

Past research has not differentiated between the left- and right-handed versions of a molecule discovered in interstellar space.

“These spectra are like your hands’ shadows,” said study author Brandon Carroll, a chemistry graduate student at CalTech. “It’s impossible to tell if a right hand or a left hand is casting the shadow.”

Every organism on Earth uses one, and just one handedness of many kinds of chiral molecules.Known as homochirality, the phenomenon has crucial ramifications for biological structure, like DNA’s double helix. Researchers do not yet know how biology came to depend on one handedness and not the other. The answer may be discovered in how these molecules naturally develop in space before being integrated into asteroids and comets and later placed on young planets.

“Meteorites in our solar system contain chiral molecules that predate the Earth itself, and chiral molecules have recently been discovered in comets,” Carroll said. “Such small bodies may be what pushed life to the handedness we see today.”

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Image credit: Brett A. McGuire. Foreground: P. Brandon Carroll

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