Astrobiology. 2018 Jun;18(6):619-629. doi: 10.1089/ast.2018.1862. Epub 2018 May 9.

Exoplanet Biosignatures: At the Dawn of a New Era of Planetary Observations.

Kiang NY^1,^2,³, Domagal-Goldman S^2,^3,⁴, Parenteau MN^3,⁵, Catling DC^3,⁶, Fujii Y⁷, Meadows VS^3,⁸, Schwieterman EW^3,^9,^10,¹¹, Walker SI^11,^12,^13,¹⁴.

Author information

1: 1 NASA Goddard Institute for Space Studies (GISS) , New York, New York, USA .
2: 2 Nexus for Exoplanet System Science , ROCKE-3D Team, NASA GISS, USA .
3: 3 NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington , Seattle, Washington, USA .
4: 4 NASA Goddard Space Flight Center , Greenbelt, Maryland, USA .
5: 5 NASA Ames Research Center , Exobiology Branch, Mountain View, California, USA .
6: 6 Department of Earth and Space Sciences/Astrobiology Program, University of Washington , Seattle, Washington, USA .
7: 7 Earth-Life Science Institute, Tokyo Institute of Technology , Ookayama, Meguro, Tokyo, Japan .
8: 8 Astronomy Department, University of Washington , Seattle, Washington, USA .
9: 9 Department of Earth Sciences, University of California , Riverside, California, USA .
10: 10 NASA Postdoctoral Program, Universities Space Research Association , Columbia, Maryland, USA .
11: 11 Blue Marble Space Institute of Science , Seattle, Washington, USA .
12: 12 School of Earth and Space Exploration, Arizona State University , Tempe, Arizona, USA .
13: 13 Beyond Center for Fundamental Concepts in Science, Arizona State University , Tempe, Arizona, USA .
14: 14 ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University , Tempe, Arizona, USA .

Abstract

The rapid rate of discoveries of exoplanets has expanded the scope of the science possible for the remote detection of life beyond Earth. The Exoplanet Biosignatures Workshop Without Walls (EBWWW) held in 2016 engaged the international scientific community across diverse scientific disciplines, to assess the state of the science and technology in the search for life on exoplanets, and to identify paths for progress. The workshop activities resulted in five major review papers, which provide (1) an encyclopedic review of known and proposed biosignatures and models used to ascertain them (Schwieterman et al., 2018 in this issue); (2) an in-depth review of O₂ as a biosignature, rigorously examining the nuances of false positives and false negatives for evidence of life (Meadows et al., 2018 in this issue); (3) a Bayesian framework to comprehensively organize current understanding to quantify confidence in biosignature assessments (Catling et al., 2018 in this issue); (4) an extension of that Bayesian framework in anticipation of increasing planetary data and novel concepts of biosignatures (Walker et al., 2018 in this issue); and (5) a review of the upcoming telescope capabilities to characterize exoplanets and their environment (Fujii et al., 2018 in this issue). Because of the immense content of these review papers, this summary provides a guide to their complementary scope and highlights salient features. Strong themes that emerged from the workshop were that biosignatures must be interpreted in the context of their environment, and that frameworks must be developed to link diverse forms of scientific understanding of that context to quantify the likelihood that a biosignature has been observed. Models are needed to explore the parameter space where measurements will be widespread but sparse in detail. Given the technological prospects for large ground-based telescopes and space-based observatories, the detection of atmospheric signatures of a few potentially habitable planets may come before 2030. Key Words: Exoplanets-Biosignatures-Remote observation-Spectral imaging-Bayesian analysis. Astrobiology 18, 619-626.