The Light in the Search for Aliens

Author:  Karuna Meda
Institution:  University of Pennsylvania

Our fascination with extraterrestrial life has grown over the years, with the first unmanned voyage to Mars and the iconic hollow-eyed, slithery green alien frequenting sci-fi movies and novels. Are aliens simply objects of the imagination, or have we just not looked long and far enough? A scientific team working at the National Institute of Standards and Technology (NIST) has used a novel approach to answer this elusive question. The researchers, led by Thom Germer, claim that extra terrestrial life may be found even before it leaves its home- the secret lies in the "handedness" of light.

The research team created and utilized a device that shines light upon plant leaves and bacteria, and afterwards they identified from a short distance the polarized reflections from the chlorophyll in these leaves and bacteria. The device successfully detected chirality- or handedness' from both the plants and bacteria. So what exactly is chirality? All organic molecules have a certain chirality,' defined as the direction in which a molecule rotates polarized light. According to scientists, this handedness' may be used to detect biochemical features of a planet's landscape, rather than spotting aliens directly. A right-handed molecule and a left-handed molecule differ in their chemical properties; this difference can be detected by the device Germer and his colleagues built to reveal if molecules indicative of "life" are present on a planet. Furthermore, the device can use chirality to look for telltale signs that life may have influenced a planetary landscape.

"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," says Germer, a physicist at the institute. "But amino acids, sugars, DNA,each of these substances is either right- or left-handed in every living thing."

What is the unique property of chiral molecules that might allow us to detect life? While both living and non-living molecules have the ability to rotate polarized light, living molecules can reproduce and their offspring will inherit the same chiral properties. As a population of these molecules grows, there will be an evident bias towards a particular handedness.

"If the surface had just a collection of random chiral molecules, half would go left, half right," Germer explains. "But life's self-assembly means they all would go one way. It's hard to imagine a planet's surface exhibiting handedness without the presence of self-assembly, which is an essential component of life."

Gremer and his colleagues say that the device needs to be improved and tested with a broad range of organic molecules, but they are hopeful of its potential use in large telescopes and space probes in the future. The search for aliens is more exciting than it has ever been, but only time will tell if we are really the only living creatures in this universe.

Written By: Karuna Meda

Edited by: News and Features Editor Yangguang Ou and Senior News and Features Editor Falishia Sloan

Published by Falishia Sloan