Water-planets in the habitable zone: atmospheric chemistry, observable features, and the case of kepler-62e and -62f

Abstract

Planets composed of large quantities of water that reside in the habitable zone are expected to have distinct geophysics and geochemistry of their surfaces and atmospheres. We explore these properties motivated by two key questions: whether such planets could provide habitable conditions and whether they exhibit discernable spectral features that distinguish a water-planet from a rocky Earth-like planet. We show that the recently discovered planets Kepler-62e and -62f are the first viable candidates for habitable zone water-planets. We use these planets as test cases for discussing those differences in detail. We generate atmospheric spectral models and find that potentially habitable water-planets show a distinctive spectral fingerprint in transit depending on their position in the habitable zone.