Researchers from LPSC have taken a giant step toward solving the mystery of why sulfur is rare in space. This is particularly exciting because sulfur is the 10th most abundant element in the universe. Sulfur’s a big part of that—forming planets, stars, and even the molecular building blocks of life. The researchers — astrophysicist Ryan Fortenberry, Ralf Kaiser and Samer Gozem — revealed their discoveries in a paper published recently in the journal Nature. Their study provides a possible roadmap for astronomers to explore this mysterious substance further.
The research reveals that while sulfur-bearing molecules have been identified in the interstellar medium, sulfur remains surprisingly rare in clouds of cosmic dust and gas. This riddle of the natural world has baffled scientists for decades. This challenge is uniquely baffling because sulfur is extremely important for life and abundant in many other chemical forms. The study shines a light on two distinct stable configurations of sulfur that can form in cold regions of space: octasulfur crowns and polysulfane chains.
The Role of Sulfur in the Universe
Sulfur is necessary to the chemical reactions that formed life and the stars. As the 10th most abundant element in the cosmos, it plays key roles in photosynthesis, geomicrobiology, and other biological and geological processes. One of its most familiar forms, octasulfur (S 8 ), is made up of eight sulfur atoms in a crown-like ring structure. This rare cross-section allows it to be incredibly stable in even the most challenging environmental conditions.
Researchers had previously inferred that sulfur-rich molecules were abundant in the icy outskirts of interstellar space. In practice, the actual detection of these molecules in molecular clouds has not matched that excitement. According to Ralf Kaiser, “The observed amount of sulfur in dense molecular clouds is less—compared to predicted gas-phase abundances—by three orders of magnitude.” This difference leads to fundamental questions about sulfur’s behavior under such extreme cosmic conditions.
Investigating Sulfur’s Cosmic Puzzle
The work by Fortenberry, Kaiser, and Gozem serves as a powerful reminder that we must continue to ask difficult questions regarding astrochemistry. “The thing that I love about astrochemistry is that it forces you to ask hard questions, then forces you to come up with creative solutions,” Fortenberry stated. One of the reasons is that how researchers used to tell if sulfur’s being detected just isn’t telling the whole story, their findings imply.
Fortenberry elaborated on the limitations faced by astronomers: “If you use, for instance, the James Webb Space Telescope, you get a specific signature at specific wavelengths for oxygen and carbon and nitrogen and so forth. When you do that for sulfur, it’s out of whack, and we don’t know why there isn’t enough molecular sulfur.” This finding has led to a reassessment of how researchers look for such elusive molecules.
Armed with their new understanding, the team suggests that polysulfane molecules could be the key to answering sulfur’s cosmic mystery. These molecules can only be positively detected once they have been sublimated into the gas phase, such as in star-forming regions. This research brings a fresh perspective to how astronomers might find sulfur compounds in space. It discusses how these novel compounds can further teach us about cosmic chemistry.
Implications for Future Research
The research represents a significant step forward in understanding molecular sulfur, which may lead to new innovations. Fortenberry suggests that “if we gain a better understanding of what the chemistry of sulfur can do, the technological commercialization that can come from that can only be realized with a foundation of fundamental knowledge.”
These findings underscore the obvious scientific importance of sulfur, as well as its commercial importance to many industries. Hydrogen sulfide is a well-studied sulfur-containing important toxicant with profound biological effects. It touches and serves as the backdrop for almost everything, from acid rain to volcanic activity.
Kaiser noted, “Laboratory simulations of interstellar conditions such as this study discover possible inventories of sulfur-containing molecules that can be formed on interstellar ices.” This study paints an optimistic picture of astrochemistry’s future. Though daunting, scientists are out there pushing the boundaries of what we know about our universe every day.