Conceptual artwork of phosphine in space. This is a molecule, PH3, consisting of a single atom of hydrogen and three atoms of phosphorus. It is a very toxic, colourless and flammable gas. Phosphine has been found in the atmospheres of Saturn, Jupiter and, more recently, Venus, where it has been suggested as the byproduct of biological processes. It has also been detected in the emission jets of the comet 67P/Churyumov-Gerasimenko, as well as in interstellar gas clouds.