SpaceThe essential guide to proving we’ve found alien life From mudstones on Mars to strange gases in exoplanet atmospheres, tentative evidence for extraterrestrial life is starting to come thick and fast. But when we've found it, how will we know for sure? Features
EarthThe audacious quest to light up the sky with artificial auroras How a Finnish physicist named Karl Lemström once became obsessed with recreating the aurora borealis from scratch – and may have ended up creating something even more intriguing Features