Статья

Detectability of Life Using Oxygen on Pelagic Planets and Water Worlds

Donald M. GlaserSchool of Molecular Sciences, Arizona State University, USA; [email protected]Hilairy E. HartnettSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Steven J. DeschSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Cayman T. UnterbornSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Ariel D. AnbarSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Steffen BuesseckerSchool of Life Sciences, Arizona State University, USATheresa FisherSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Steven D. GlaserSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Stephen R. KaneDepartment of Earth and Planetary Sciences, University of California, Riverside, USAC. M. LisseApplied Physics Laboratory, Johns Hopkins University, USACamerian MillsapsSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]Susanne NeuerSchool of Life Sciences, Arizona State University, USAJ. G. O’RourkeSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]N. SantosInstituto de Astrofísica e Ciências do Espaço, Universidade do Porto, PortugalSara Imari WalkerSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]M. Yu. ZolotovSchool of Earth and Space Exploration, Arizona State University, USA; [email protected]

2020en

ABI

Аннотация

Abstract The search for life on exoplanets is one of the grand scientific challenges of our time. The strategy to date has been to find (e.g., through transit surveys like Kepler) earthlike exoplanets in their stars’ habitable zone, then use transmission spectroscopy to measure biosignature gases, especially oxygen, in the planets’ atmospheres (e.g., using James Webb Space Telescope (JWST)). Already there are more such planets than can be observed by JWST, and missions like the Transiting Exoplanet Survey Satellite and others will find more. A better understanding of the geochemical cycles relevant to biosignature gases is needed, to prioritize targets for costly follow-up observations and to help design future missions. We define a Detectability Index to quantify the likelihood that a biosignature gas could be assigned a biological versus nonbiological origin. We apply this index to the case of oxygen gas, O 2 , on earthlike planets with varying water contents. We demonstrate that on earthlike exoplanets with 0.2 weight percent (wt%) water (i.e., no exposed continents) a reduced flux of bioessential phosphorus limits the export of photosynthetically produced atmospheric O 2 to levels indistinguishable from geophysical production by photolysis of water plus hydrogen escape. Higher water contents >1 wt% that lead to high-pressure ice mantles further slow phosphorus cycling. Paradoxically, the maximum water content allowing use of O 2 as a biosignature, 0.2 wt%, is consistent with no water based on mass and radius. Thus, the utility of an O 2 biosignature likely requires the direct detection of both water and land on a planet.

Перевод пока недоступен

Идентификаторы

DOI: 10.3847/1538-4357/ab822d

Цитирования и источники

Цитирований: 2Использованных источников: 0

Показатели — AkademScholar