Recent research has shown that planets orbiting cool stars are potentially susceptible to the abiotic accumulation of oxygen, often considered a key biosignature. A new study led by UW doctoral student Edward Schwieterman and Professor Victoria Meadows has found that these potential “false positives” for life are accompanied by other spectral signatures that would indicate their abiotic origin. If abiotic oxygen is produced through CO2 photolysis, CO would also be also be observable in transit transmission observations. If the abiotic oxygen is from a history of massive hydrogen escape, the substantial oxygen atmosphere that would remain could be identified by pressure-sensitive O4 features in transmission or reflected light observations. This information can help inform future astronomical biosignature surveys of nearby planetary systems. The paper has been published in the Astrophysical Journal Letters. UW Astronomy graduate students Rodrigo Luger and Giada Arney and VPL researchers Shawn Domagal-Goldman, Drake Deming, Sonny Harman, Amit Misra, and Rory Barnes also contributed.