Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life
PublisherMary Ann Liebert Inc.
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AbstractIn the coming years and decades, advanced space-and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere. Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a comprehensive overview of our current understanding of potential exoplanet biosignatures, including gaseous, surface, and temporal biosignatures. We additionally survey biogenic spectral features that are well known in the specialist literature but have not yet been robustly vetted in the context of exoplanet biosignatures. We briefly review advances in assessing biosignature plausibility, including novel methods for determining chemical disequilibrium from remotely obtainable data and assessment tools for determining the minimum biomass required to maintain short-lived biogenic gases as atmospheric signatures. We focus particularly on advances made since the seminal review by Des Marais et al. The purpose of this work is not to propose new biosignature strategies, a goal left to companion articles in this series, but to review the current literature, draw meaningful connections between seemingly disparate areas, and clear the way for a path forward. Copyright 2018 Edward W. Schwieterman et al.
SponsorsThis work was also supported by the NASA Astrobiology Institute, including the VPL under Cooperative Agreement Number NNA13AA93A and the Alternative Earths team under Cooperative Agreement Number NNA15BB03A. S.D. acknowledges support from NASA exobiology grant NNX15AM07G. The research of R.H. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Identifier to cite or link to this itemhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85042219205&doi=10.1089%2fast.2017.1729&partnerID=40&md5=b19d0667da12a02aadd3ed2deb0a6cd0; http://hdl.handle.net/10713/9712