July 28, 2021 updates Posted on July 28, 2021 by Doug Loss Oxygenation, Life, and the Planetary System during Earth’s Middle History: An Overview https://liebertpub.com/doi/10.1089/ast.2020.2418 Assessment of Ammonia as a Biosignature Gas in Exoplanet Atmospheres https://arxiv.org/abs/2107.12424 The Keck Planet Imager and Characterizer: A dedicated single-mode fiber injection unit for high resolution exoplanet spectroscopy https://arxiv.org/abs/2107.12556