The Case of the Missing Sulfur: Chemists Find Answers in Space

Clouds of cosmic dust and gas contain many of the building blocks needed for life, but sulfur is mysteriously rare. One of the most common forms of sulfur is S8, a ring of sulfur atoms that form a crown-like structure. A team of astrochemists, including an Ole Miss researcher, has discovered that  the crowns may help point scientists in the right direction. Credit Graphic by John McCustion/University Marketing and Communications

For decades, scientists have been puzzled by a strange cosmic riddle: sulfur, one of the universe’s most common elements and essential to life, seems to be missing in space. Now, a new study may have uncovered where it’s been hiding all along.

An international team of researchers — including astrochemist Ryan Fortenberry (University of Mississippi), chemist Ralf Kaiser (University of Hawaii at Mānoa), and computational chemist Samer Gozem (Georgia State University) — has published fresh insights in Nature Communications that could change how astronomers search for sulfur among the stars.

“Hydrogen sulfide is everywhere on Earth — from volcanoes to coal-fired power plants, even in the chemistry that drives acid rain,” Fortenberry explained. “If we understand sulfur chemistry in space, we can better grasp its role not just in astronomy, but also in technology here on Earth.”

Despite being the 10th most abundant element in the universe, sulfur has been notoriously elusive in interstellar space. Observations suggest that dense molecular clouds contain far less sulfur than predicted — off by a staggering factor of a thousand.

So where is it?

The answer, it seems, could be frozen in interstellar ice. In the extreme cold of space, sulfur atoms don’t just float around freely. Instead, they can lock into two main forms:

octasulfur crowns (rings of eight sulfur atoms arranged like tiny crowns)

polysulfanes (long chains of sulfur atoms connected with hydrogen).

These stable molecules cling to icy dust grains, effectively “hiding” sulfur in solid form.

That helps explain why space telescopes, like the James Webb Space Telescope, struggle to detect sulfur the same way they do oxygen, carbon, or nitrogen. “When you look for sulfur, the signals are off,” said Fortenberry. “It’s not that it isn’t there — it’s just in a form we weren’t looking for.”

READ ALSO: Chinese firm develops world's largest LED mesh Flying Display

READ ALSO: Northrop Grumman Successfully Tests World’s Most Powerful Rocket Booster for NASA Moon Missions

The team’s experiments simulated the icy, low-temperature conditions of deep space, showing that these sulfur compounds could be surprisingly abundant. Astronomers may soon be able to look for them directly, especially once these ices warm up in star-forming regions and release sulfur molecules into the gas phase, where radio telescopes can spot them.

But sulfur is tricky. Unlike more stable elements, its molecules don’t sit still. They constantly shift between rings, chains, and other shapes. “It never maintains the same structure,” Fortenberry said. “It’s kind of like a virus — always changing.”

Still, identifying these stable sulfur-rich candidates gives astronomers a new roadmap in their cosmic treasure hunt. And for Fortenberry, that’s what makes astrochemistry so exciting: “It forces us to ask hard questions and come up with creative answers. And those answers often lead to unexpected, positive breakthroughs.”

So while sulfur may have been hiding in plain sight — frozen in the ices of space — scientists are finally getting closer to solving one of astronomy’s most enduring mysteries.