Astronomers and other planetary scientists have confirmed the significant presence of phosphine gas on Venus, which they believe signals extraterrestrial life, according to a pair of papers published Monday in Nature. On Earth, phosphine is found in the human gut, some types of animal feces, deep sea worms and in environments that house anaerobic bacteria. Building off a Cardiff University researcher’s 2017 telescope observation of phosphine gas in Venus’ atmosphere, the team of researchers observed concentrations of the gas 20 times higher than in the Earth’s atmosphere and ran computer simulations to test different hypotheses as to why. The researchers assert that although phosphine can be synthesized without life on larger planets like Jupiter and Saturn, smaller, rocky planets like Earth and Venus need anaerobic life to manufacture the volatile gas. Other scientists question their work, however, and the means by which Earth microbes make phosphine is still unclear.

“We’ve seen it associated with where microbes are at, but we have not seen a microbe do it, which is a subtle difference, but an important one,” said Matthew Pasek, a geoscientist at the University of South Florida, who was not involved in the study. Monday’s study, however, may help convince NASA to fund Venus exploration efforts, with NASA announcing it would consider a proposal for a pair of Venus spacecraft in a funding competition earlier this year.