Sulfur And ET

Scientists trying to develop techniques to find life on exoplanets similar to Earth have added sulfur to their quiver. Since some molecules on Earth eat sulfur and release sulfurous oxide, for example, they reason finding either of those in the atmosphere of an Earth-like exoplanet could suggest life.

Of course, sulfur would be only one marker. Evidence of photosynthesis occurring would be an obvious indicator of possible life, for example. Since oxygen quickly combines with other elements, the presence of free oxygen in an atmosphere would suggest some process is constantly replenishing the oxygen. That process may be life.

The spectroscopic signature of a vibrant biosphere is likely to be extremely complex. Teasing several markers from the data instead of relying on any single one will probably be what finally clinches the case for science.