Chiral Molecule Detected in Interstellar Space
Like a pair of human hands, certain organic molecules have mirror-image versions of themselves, a chemical property known as chirality. These so-called "handed" molecules are essential for biology and have intriguingly been found in meteorites on Earth and comets in our Solar System. None, however, has been detected in the vast reaches of interstellar space, until now.
A team of scientists using highly sensitive radio telescopes have discovered the first complex organic chiral molecule in interstellar space. The molecule, propylene oxide (CH3CHOCH2), was found near the center of our Galaxy in an enormous star-forming cloud of dust and gas known as Sagittarius B2 (Sgr B2).
The research was undertaken primarily with the National Science Foundation’s Green Bank Telescope (GBT) in West Virginia as part of the Prebiotic Interstellar Molecular Survey. Additional supporting observations were taken with the Parkes radio telescope in Australia.
“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, a chemist and Jansky Postdoctoral Fellow with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia.
“Propylene oxide is among the most complex and structurally intricate molecules detected so far in space,” said Brandon Carroll, a chemistry graduate student at 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.”
McGuire and Carroll share first authorship on a paper published in the journal Science. They also are presenting their results at the American Astronomical Society meeting in San Diego, California.
Every living thing on Earth uses one, and only one handedness of many types of chiral molecules. This trait, called homochirality, is critical for life and has important implications for many biological structures, including DNA’s double helix. Scientists do not yet understand how biology came to rely on one handedness and not the other. The answer, the researchers speculate, may be found in the way these molecules naturally form in space before being incorporated into asteroids and comets and later deposited 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,” noted Carroll. “Such small bodies may be what pushed life to the handedness we see today.”
“By discovering a chiral molecule in space, we finally have a way to study where and how these molecules form before they find their way into meteorites and comets, and to understand the role they play in the origins of homochirality and life,” McGuire said.