2019ApJ...883..143L

We show that the total habitable volume in the atmospheres of cool brown dwarfs with effective temperatures of ∼250-350 K is possibly larger by 2 orders of magnitude than that of Earth-like planets. We also study the role of aerosols, nutrients, and photosynthesis in facilitating life in brown dwarf atmospheres. Our predictions might be testable through searches for spectral edges in the near-infrared and chemical disequilibrium in the atmospheres of nearby brown dwarfs that are either free-floating or within several au of stars. For the latter category, we find that the James Webb Space Telescope may be able to achieve a signal-to-noise ratio of ∼5 after a few hours of integration time per source for the detection of biogenic spectral features in ∼10³ cool brown dwarfs.