Any life that uses sulfur for the backbones of complex molecules in its biology is likely to mix it with other elements, not just on side chains but in the backbone chain itself. In this respect, it is similar to Nitrogen and Phosphorus-Based Life and Boron-Based Life, but even our biochemistry uses a mixture of elements, as the polypeptides that make up proteins have a spine made from carbon and nitrogen, and the twenty or so side chains they use to create a vast array of possibilities contain many different elements. An alien species might have an even more irregular mix.
A nitrogen-sulfur polymer may work as the backbone for complex structures. Neither of these elements would work well on their own, yet between them, life might just be a possibility. They would use polymers made from alternate nitrogen and sulfur atoms with side chains attached to the nitrogen. In acidic water, they would break down into simple molecules, but the polymers are more stable under neutral and alkaline conditions. A sulfur atom can act as a link between molecules based on carbon, as well. As opposed to organic chains with different side groups stuck to them, life might use different organic segments linked by sulfur bridges.
There does not seem be any fundamental reason why nitrogen-sulfur or organic-sulfur life could not live at the same temperatures, breathe the same air and drink the same water as us, except that it may be likely to have originated in different conditions and evolved to match them. For example, it may be that worlds with higher levels of sulfur mostly support Sulfur-Breathing Life. They would, of course, require different nutrients either way, and may be associated with unpleasant, pungent sulfur compounds.
Game and Story Use
- Finding out the biology and hence needs of an alien species may be used as a puzzle, and a sulfurous biology could be a part of it.
- What would a nitrogen-sulfur species be like? It's not an easy question, but we can speculate on a few things.
- We know as much that they'd have a pungent odor and need food that contains sulfur.
- They would need to regulate their acidity levels well, and dead matter would break down quickly when exposed to mild acids.
- As sulfur bridges are responsible for the toughness of animal hairs, horns and nails, they might be quite robust in their composition.
- Any shells or other mineral parts might be made from iron sulfide or a similar compound.