The toxic trace gas phosphine is known on Earth as a metabolic product of bacteria and could indicate biological processes in the Venus atmosphere. Not a haven for life: Dense clouds surround Venus at an altitude of about 50 to 70 kilometers. Phosphine does not exist in the atmosphere.

Why is phosphine on Venus?

If phosphides bound in metals like iron, from Venus' deep mantle are ejected into its atmosphere with enough explosive force, they can rise high enough to interact with sulfuric acid and thus form phosphine, Truong said in a statement.

Where can phosphine be found?

Phosphine is a chemical compound made up of one atom of phosphorus and three atoms of hydrogen, and scientists have also spotted it on Earth, Jupiter and Saturn. On the gas giants, it's quite prevalent in the atmospheres, both of which are rich in hydrogen.