The molecular astrobiologist argued astronomers now need to consider new and bizarre scenarios if we are to find alien life one day.
Dr Sousa-Silva, who led the phosphine study, said: “Here on Earth, oxygen is a really impressive sign of life. But other things besides life make oxygen too.
“It’s important to consider stranger molecules that might not be made as often, but if you do find them on another planet, there’s only one explanation.”
Creatures that do not rely on oxygen to grow are known as anaerobic organisms or anaerobes.
Here on Earth, anaerobes are commonly single-celled bacteria that process hydrogen, for instance, instead of oxygen.