For years, astrochemists have been on a cosmic scavenger hunt for sulfur, a life-essential factor. They anticipated to seek out it sprinkled generously throughout the universe, primarily in chilly clouds of gasoline and mud the place stars are born. However shock! There’s manner much less sulfur on the market than their fashions predicted.
This thriller, referred to as the sulfur depletion drawback, has puzzled researchers for many years. It’s like planning a feast and realizing the principle ingredient is lacking. The place did all of the sulfur go?
A global staff of researchers, together with Ryan Fortenberry, an astrochemist on the College of Mississippi, Ralf Kaiser, professor of chemistry on the College of Hawaii at Mānoa, and Samer Gozem, computational chemist at Georgia State College, might level to the place it has been hiding. A greater understanding of sulfur’s chemistry and the technological commercialization that may consequence requires a basis in basic information.
In dense molecular clouds, scientists anticipated to seek out numerous sulfur floating round as gasoline. However what they discovered was a thousand instances lower than predicted. That’s an enormous hole! So the place’s it hiding?
Astronomers solve Sulfur mystery with Ammonium Hydrosulfide salt
The reply could be frozen in plain sight: interstellar ice. In these icy areas, sulfur can shape-shift into two sneaky varieties: Octasulfur crowns, through which eight sulfur atoms are linked in a hoop, like a tiny golden crown, and Polysulfanes, the place chains of sulfur atoms are held along with hydrogen, like molecular spaghetti.
These varieties persist with icy dust grains, locking sulfur away in strong type, making it invisible to telescopes that search for gasoline.
As Fortenberry explains, “telescopes just like the James Webb can simply spot components like oxygen and carbon by their gentle signatures. However whenever you do this for sulfur, it’s out of whack, and we don’t know why there isn’t sufficient molecular sulfur.”
“What this work is exhibiting is that the most typical types of sulfur that we already find out about are most likely the place the sulfur is hiding.”
This new analysis means that sulfur-rich molecules may very well be hiding within the icy corners of area, ready to be found. In lab simulations mimicking interstellar circumstances, they confirmed how sulfur might bond into polysulfanes and different shapes on frozen mud grains. These molecules could be frequent in area ice, and when that ice warms up in star-forming areas, the sulfur escapes into gasoline, able to be noticed by radio telescopes.
So as an alternative of searching for sulfur in its typical varieties, astronomers now have a brand new set of clues: seek for the shapes sulfur prefers when it’s frozen.
However right here’s the twist: sulfur is a shapeshifter. It doesn’t quiet down. It morphs from rings to chains to different wild varieties, like a molecular chameleon. Or as Fortenberry places it, “It’s sort of like a virus – because it strikes, it adjustments.”
Their work doesn’t simply resolve a puzzle; it opens up an entire new mind-set. By figuring out secure sulfur shapes, they’ve given astronomers targets to hunt for within the huge interstellar medium.
Journal Reference:
- Herath, A., McAnally, M., Turner, A.M., et al. Lacking interstellar sulfur in inventories of polysulfanes and molecular octasulfur crowns. Nat Commun 16, 5571 (2025). DOI: 10.1038/s41467-025-61259-2
