Sulfur is one of the most abundant elements in the universe. If you peer into a diffuse interstellar cloud, you find loads of it - about the amount expected based on fusion patterns of the stars it was born in. However, if you look at a dense, cold, molecular cloud - the kind where those stars actually form - it seems like 99% of the sulfur that is expected to be there is missing. Scientists have puzzled over this missing sulfur problem for decades, though a leading theory is that the element hides on icy dust grains making it hard to detect. A new paper published in Astronomy & Astrophysics from the Max Planck Institute for Extraterrestrial Physics and the Centro de Astrobiologia describes a new computer simulation model that they aimed to support the interpretation of laboratory results and test our current understanding of sulfur evolution in interstellar ices.