Scientists now can work out what the atmospheres of worlds outside our solar system are made of. Using the James Webb Space Telescope, we have seen water, carbon dioxide, methane, and other gases. Could we, from this distance, know how those gases formed? Possibly. Looking for planets with signs of being intentionally changed - terraforming - would give us proof of an advanced civilization, and a new paper explores just how the investigation process would work. Senior astronomer Franck Marchis talks with authors Edward W. Schwieterman and Daniel Angerhausen about what these gases would be and why they would work as evidence of life. (Recorded 28 August 2024.)