Exoplanet Biosignatures: Future Directions


Extrasolar planet

Exoplanet science promises a continued rapid accumulation of rocky planet observations in the near future, energizing a drive to understand and interpret an unprecedented wealth of data to search for signs of life. The large statistics of exoplanet samples, combined with the ambiguity of our understanding of universal properties of life and its signatures, necessitate a quantitative framework for biosignature assessment.

In anticipation of the large, broad, biased, and sparse data that will be generated in the coming years, we present here a Bayesian framework that leverages the diversity of disciplinary perspectives that must come to bear on the problem of detecting alien life. The framework quantifies metrics for the detectability of signs of life in terms of the likelihoods of being produced by non-living or living processing, providing a language to define the conditional probabilities and confidence levels of future life detection. Importantly, the statistical approach adopted provides a framework for constraining the prior probability of life with or without positive detection.

We lay out a framework that addresses how the detectability of life necessarily requires understanding: 1) what is not life; 2) the processes of life, spanning the molecular to planetary scales, and scales of seconds to billions of years; and 3) the prior probabilities for the emergence of life and the universals of biological innovation. The goal is to develop a quantitative framework that is not entrained to specific definitions for life or its signatures, and instead frames the problem of remote detection of life in terms of what is observable and what we can infer from those observables based on what is known about non-living and living processes.

Sara I. Walker, William Bains, Leroy Cronin, Shiladitya DasSarma, Sebastian Danielache, Shawn Domagal-Goldman, Betul Kacar, Nancy Y. Kiang, Adrian Lenardic, Christopher T. Reinhard, William Moore, Edward W. Schwieterman, Evgenya L. Shkolnik, Harrison B. Smith
(Submitted on 23 May 2017)

Comments: 69 pages, 13 figures; The paper is the fourth in a series of 5 review manuscripts of the NExSS Exoplanet Biosignatures Workshop. Community commenting is solicited at this url: this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1705.08071 [astro-ph.EP] (or arXiv:1705.08071v1 [astro-ph.EP] for this version)
Submission history
From: Sara Walker
[v1] Tue, 23 May 2017 04:10:10 GMT (2497kb)

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