When the James Webb Space Telescope detected potential biosignatures in the atmosphere of K2-18 b last year, the discovery sparked intense debate. Here was a sub-Neptune exoplanet 124 light years away, possibly harboring methane, carbon dioxide, and even dimethyl sulfide, which is a gas produced by phytoplankton on Earth. But before we get too excited about alien life, it's necessary to understand if this planet's atmosphere can even survive the harsh environment of the host star.