By Jacopo Prisco, CNN
(CNN) — Scientists have discovered the largest organic molecule containing sulfur — a key ingredient for life — ever identified in interstellar space. The researchers call the discovery a “missing link” in scientists’ understanding of the cosmic origins of life’s chemistry.
Sulfur is the 10th most abundant element in the universe and a critical component of amino acids, proteins and enzymes on Earth. But while researchers had previously found sulfur-bearing molecules similar to the newly discovered one in comets and meteorites, there was a puzzling lack of large molecules including sulfur in interstellar space — the vast region between stars that is scattered with clouds of dust and gas.
“Sulfur came to Earth from space long, long ago,” said Mitsunori Araki, a scientist at the Max Planck Institute for Extraterrestrial Physics in Germany and lead author of a study on the discovery, which was published last week in the journal Nature Astronomy.
“However, we have only found a very limited amount of sulfur-bearing molecules in space, which is strange. It should exist in huge amounts, but it’s very difficult to find.”
A different team of researchers previously suggested that sulfur might appear to be rare in space because it’s trapped in cosmic ice — hiding in plain sight rather than missing.
The new detection, therefore, adds an important piece to this puzzle. “This is the largest sulfur-bearing molecule ever found in space, at 13 atoms,” Araki said. “Before this one, the largest only had nine atoms, but it was already a rare case, because most detected sulfur-bearing molecules only had three, four or five atoms.”
Finding larger molecules is important, he added, because it helps to fill an existing gap between simple chemistry found in space and the more complex building blocks of life that have been discovered in comets and meteorites.
The molecule, which also contains carbon and hydrogen, is called 2,5-cyclohexadiene-1-thione and adds to a growing catalog of over 300 molecules observed in space so far. The finding, Araki said, suggests that many more molecules containing sulfur, perhaps even larger, could be detected in the future.
Stellar nurseries
The molecule was found within a molecular cloud called G+0.693–0.027 about 27,000 light years from Earth, near the center of our galaxy.
Molecular clouds are cold and dense concentrations of dust and gas that allow for the formation of molecules. They act as stellar nurseries as gravity creates clumps that eventually become baby stars.
“A molecular cloud is where star formation is happening,” said Valerio Lattanzi, also a scientist at the Max Planck Institute for Extraterrestrial Physics and a coauthor of the study.
Eventually, Lattanzi added, some of these clouds will lead to the formation of planetary systems like our own solar system. “The ingredients that are embedded in the molecular cloud will be transferred to the planets,” he said. “We are trying to find out what the ingredients that will eventually form life are, trying to understand how from simple molecules we get to life as we know it on Earth. And we are trying to add elements to this picture, one by one.”
Researchers first synthesized the molecule by applying an electric discharge to a substance called thiophenol — a foul-smelling liquid containing sulfur