Scientists reported phosphine in Venus's clouds in 2020, then watched the finding come under fierce attack. But years of follow-up observations have repeatedly recovered the signal with far more data, while no known non-biological process has yet been shown to produce the claimed amounts.

Scientists reported phosphine in Venus's clouds in 2020, then watched the finding come under fierce attack. But years of follow-up observations have repeatedly recovered the signal with far more data, while no known non-biological process has yet been shown to produce the claimed amounts.

The phosphine argument at Venus did not end when the original result was challenged. Reprocessed ALMA observations, a disputed reanalysis of SOFIA data and a far larger monitoring programme with the James Clerk Maxwell Telescope have all recovered candidate signals. That makes the 2020 finding harder to dismiss as one bad spectrum. It does not make phosphine universally accepted, and it does not establish life in the clouds. Three questions are …