Washington | A complex organic molecule essential for biology has been discovered for the first time in interstellar space, a finding that may help understand how life originated in the universe. Like a pair of human hands, certain organic molecules have mirror-image versions of themselves, a chemical property known as chirality.
These molecules are essential for biology and have been found in meteorites on Earth and comets in our Solar System. However, none has been detected in the vast reaches of interstellar space, until now.
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 centre of our Galaxy in an enormous star-forming cloud of dust and gas known as 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, said Brett McGuire, postdoctoral fellow at the National Radio Astronomy Observatory (NRAO) in the US.
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 the US. Complex organic molecules form in interstellar clouds like Sgr B2 in several ways.
To form complex molecules like propylene oxide astronomers believe thin mantles of ice on dust grains help link small molecules into longer and larger structures. These molecules can then evaporate from the surface of the grains and further react in the gas of the surrounding cloud.
To date, more than 180 molecules have been detected in space. Each molecule gives off a distinctive signature, a series of telltale spikes that appear in the radio spectrum. Larger and more complex molecules have a correspondingly more complex signature, making them harder to detect.
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. 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.