But scientists say smaller, rocky planets like Earth and Venus don’t have enough energy to produce a lot of phosphine in the same way. But one thing seems to be very good at making it: anaerobic life or microbial organisms that don’t need oxygen or they don’t use it.
In such worlds, “as far as we can tell, phosphine can only be produced by life,” said Dr. Sousa-Silva. She has long studied gas, based on the theory that finding that it is emitted by rocky planets orbiting distant stars may be evidence that life exists elsewhere in the Bird’s Path.
Here on Earth, phosphine is present in our gut, in the feces of badgers and penguins, in some deep-sea worms, as well as in other biological environments associated with anaerobic organisms. It is also very poisonous. The soldiers have used it for chemical warfare, and it is used as a fumigant on farms. On the TV show “Bad” protagonist Walter White forces two opponents to be killed.
But scientists have yet to explain how the Earth’s microbes do it.
“There’s not much understanding of where it comes from, how it comes from things like that,” said Matthew Pasek, a geographer at the University of South Florida in Tampa. “We’ve seen that relate to where microbes are, but we haven’t seen a microb do that, which is a subtle but important difference.”
Dr. Sousa-Silva was surprised when Dr. Greaves said he discovered phosphine.
“This moment plays a lot in my mind because I took a few minutes to consider what was going on,” she said.
If Venus really contained phosphine, she believed there could be no obvious explanation other than anaerobic life.