There’s a long history of astronomers looking for signs of life on Venus. Throughout the 19th century and into the 20th, reports circulated of a mysterious glow, known as the Ashen Light, which sporadically appeared on the planet’s night side. Could it be a product of civilisation, perhaps the glow of vast ritual bonfires breaking through the thick clouds that were known to blanket the planet? Later writers speculated about vast underground cities, or intelligent creatures who made the most of the thick atmosphere for aerial acrobatics. When spacecraft finally visited our neighbouring planet, in the 1960s, dreams of life on Venus receded. A runaway version of the greenhouse effect has changed what may once have been a pleasant world to a decent approximation of hell; the surface temperature is hot enough to melt lead, the pressure on the ground high enough to crush a visiting astronaut, and those thick clouds are mostly sulphuric acid. A few dreamers still wrote of floating cities in Venusian clouds, but attention turned to Mars as the best bet for searching for past or present life. Until this week, that is.