Even if there's life on TRAPPIST-1, we probably can't detect it

If we ever find life on other worlds, it is unlikely to be a powerful message from space. It's certainly possible that an alien civilization specifically sends us a radio message like a scene out of Contact, but the more likely scenario is that we observe some kind of biological signature in an exoplanet's atmosphere, such as oxygen or chlorophyll. But as a recent study released on the arXiv preprint server shows, that could be more difficult than we thought.