New Insights Into The Origins Of The Chemistry Of Life

Researchers at the Max Planck Institute for Extraterrestrial Physics (MPE), in collaboration with astrophysicists from the Centro de Astrobiología (CAB), CSIC-INTA, have identified the largest sulfur-bearing molecule ever found in space: 2,5-cyclohexadiene-1-thione (C₆H₆S).

They made this breakthrough by combining laboratory experiments with astronomical observations. The molecule resides in the molecular cloud G+0.693–0.027, about 27,000 light-years from Earth near the center of the Milky Way. With a stable six-membered ring and a total of 13 atoms, it far exceeds the size of all previously detected sulfur-containing compounds in space.

“This is the first unambiguous detection of a complex, ring-shaped sulfur-containing molecule in interstellar space—and a crucial step toward understanding the chemical link between space and the building blocks of life”, says Mitsunori Araki, scientist at MPE and lead author of the study.

Until now, astronomers had only detected small sulfur compounds—mostly with six atoms or fewer—in interstellar space. Large, complex sulfur-containing molecules were expected, particularly due to sulfur’s essential role in proteins and enzymes, yet these larger molecules had remained elusive. This gap between interstellar chemistry and the organic inventory found in comets and meteorites had been a central mystery in astrochemistry.

This is a state-of-the-art self-developed laboratory spectrometer. MPE scientists Christian Endres and Mitsunori Araki (right) orchestrate the experiment: one drives the production of a new molecule, while the other captures its signatures through precision spectroscopy. At the center of the photo stands a massive vacuum chamber—the arena where a new molecule is born and immediately put under measurement. — MPE

The newly discovered C₆H₆S is structurally related to molecules found in extraterrestrial samples—and is the first of its kind definitively detected in space. It establishes a direct chemical “bridge” between the interstellar medium and our own solar system.

The team synthesized the molecule in the lab by applying a 1,000-volt electrical discharge to the evil smelling liquid thiophenol (C₆H₅SH). Using a self-developed spectrometer, they precisely measured the radio emission frequencies of C₆H₆S, producing a unique “radio fingerprint” with more than seven significant digits. This signature was then matched to astronomical data from a large observational survey led by CAB, collected with the IRAM 30m and the Yebes 40-meter radio telescopes in Spain.

“Our results show that a 13-atom molecule structurally similar to those in comets already exists in a young, starless molecular cloud. This proves that the chemical groundwork for life begins long before stars form”, says Valerio Lattanzi, Scientist at MPE.

The discovery suggests that many more complex sulfur-bearing molecules likely remain undetected—and that the fundamental ingredients of life may have formed in the depths of interstellar space, long before Earth came into existence.

Astrobiology, Astrochemistry,