The clouds of Venus may contain life. Some 50 to 60 kilometres above the surface, there are small quantities of phosphine gas, a substance that is present in Earth’s atmosphere because it is produced by microbes and by human technological processes. There are no known non-biological mechanisms of making the gas on Venus, so it may be being produced by alien microbes.

Jane Greaves at Cardiff University, UK, led a team of astronomers who looked at Venus using the James Clerk Maxwell Telescope in Hawaii and the …