How can we prove alien life when they inevitably do show up? With a slew of new missions poised to return data from alien worlds, the pace of potential discoveries is likely to accelerate. So, what questions should we ask ourselves when apparent evidence of alien life inevitably arrives? We walk you through the most plausible ways it might first show up, from faint chemical signatures to fossilised microbes. Think of it as a scientific gut-check – a sliding scale of how close different scenarios