Are Aliens Out There? Left- and Right-Handed Molecules May Hold the Answer

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Proving that life exists on distant planets may seem a near impossibility, but researchers at the National Institute of Standards and Technology (NIST) have a theory that may shed light (literally!) on the age-old question. They’d like to launch an instrument into space that could detect the “chirality”—or handedness—of the light from molecules on other planets.

Most molecules that favor life—like oxygen, for example—are chiral. This means they are either right- or left-handed. And this is where light comes in. Light polarizes off of chiral molecules necessary to life in detectable ways. By studying this polarization on other planets, NIST researchers think they might be able to detect whether life exists there.

Thom Germer, the NIST physicist leading the research, warns that the definition of “life” needs to be pretty loose. “You don’t want to limit yourself to looking for specific materials like oxygen that Earth creatures use, because that makes assumptions about what life is,” he told Science Daily. “But amino acids, sugars, DNA—each of these substances is either right- or left-handed in every living thing.”

Scientists already know that when an organism reproduces, its offspring will have chiral molecules with the same handedness. Theoretically, as life spreads on a planet, more and more molecules that favor a particular handedness would fill the landscape.

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Although the NIST team is dreaming large, they’re starting out small. So far, the team has built a device that shines light onto plant leaves and bacteria, and then detects the reflections from chlorophyll. Germer says they’ll next build a device that could be used on the surface of a pond. If they keep getting promising results, they’ll build another that could be used on an entire region on Earth, and eventually one that could be built into a large telescope or mounted on a space probe.

“What’s neat about the concept is that it is sensitive to something that comes from the process behind organic self-assembly,” Germer told Science Daily, “but not necessarily life as we know it.”