Hostname: page-component-cd9895bd7-jn8rn Total loading time: 0 Render date: 2024-12-18T11:14:22.415Z Has data issue: false hasContentIssue false
  • English
  • Français

Astrobiologists are rational but not Bayesian

Published online by Cambridge University Press:  17 June 2021

William Bains Open the ORCID record for William Bains [Opens in a new window]  and
Janusz Jurand Petkowski Open the ORCID record for Janusz Jurand Petkowski [Opens in a new window]
William Bains*
Affiliation:
Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA02139, USA School of Physics & Astronomy, Cardiff University, 4 The Parade, CardiffCF24 3AA, UK
Janusz Jurand Petkowski
Affiliation:
Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA02139, USA
*
Author for correspondence: William Bains, E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The search for biosignatures is likely to generate controversial results, with no single biosignature being clear proof of the presence of life. Bayesian statistical frameworks have been suggested as a tool for testing the effect that a new observation has on our belief in the presence of life on another planet. We test this approach here using the tentative discovery of phosphine on Venus as an example of a possible detection of a biosignature on an otherwise well-characterized planet. We report on a survey of astrobiologists' views on the likelihood of life on Enceladus, Europa, Mars, Titan and Venus before the announcement of the detection of phosphine in Venus' atmosphere (the Bayesian Prior Probability) and after the announcement (the Posterior Probability). Survey results show that respondents have a general view on the likelihood of life on any world, independent of the relative ranking of specific bodies, and that there is a distinct ‘fans of icy moons’ sub-community. The announcement of the potential presence of phosphine on Venus resulted in the community showing a small but significant increase in its confidence that there was life on Venus; nevertheless the community still considers Venus to be the least likely abode of life among the five targets considered, last after Titan. We derive a Bayesian formulation that explicitly includes both the uncertainty in the interpretation of the signal as well as uncertainty in whether phosphine on Venus could have been produced by life. We show that although the community has shown rational restraint about a highly unexpected and still tentative detection, their changing expectations do not fit a Bayesian model.

Keywords

Bayesian statisticsbiosignaturecommunitysurvey
Type
Research Article
Information
International Journal of Astrobiology , Volume 20 , Issue 4 , August 2021 , pp. 312 - 318
Check for updates
Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bains, W (2008) Random number generation and creativity. Medical Hypotheses 70, 186–190.CrossRefGoogle ScholarPubMed
Bains, W, Petkowski, JJ, Sousa-Silva, C and Seager, S (2019) New environmental model for thermodynamic ecology of biological phosphine production. Science of the Total Environment 658, 521–536.CrossRefGoogle ScholarPubMed
Bains, W, Petkowski, JJ, Seager, S, Ranjan, S, Sousa-Silva, C, Rimmer, P, Zhan, Z, Greaves, JS and Richards, AMS (2021) Phosphine on Venus cannot be explained by conventional processes. Astrobiology. in press.Google Scholar
Benneke, B and Seager, S (2012) Atmospheric retrieval for super-Earths: uniquely constraining the atmospheric composition with transmission spectroscopy. The Astrophysical Journal 753, 100.CrossRefGoogle Scholar
Catling, DC, Krissansen-Totton, J, Kiang, NY, Crisp, D, Robinson, TD, DasSarma, S, Rushby, AJ, Del Genio, A, Bains, W and Domagal-Goldman, S (2018) Exoplanet biosignatures: a framework for their assessment. Astrobiology 18, 709–738.CrossRefGoogle ScholarPubMed
Deming, LD and Seager, S (2017) Illusion and reality in the atmospheres of exoplanets. Journal of Geophysical Research: Planets 122, 53–75.Google Scholar
Gibson, NP, Pont, F and Aigrain, S (2011) A new look at NICMOS transmission spectroscopy of HD 189733, GJ-436 and XO-1: no conclusive evidence for molecular features. Monthly Notices of the Royal Astronomical Society 411, 2199–2213.CrossRefGoogle Scholar
Greaves, JS, Richards, AMS, Bains, W, Rimmer, PB, Sagawa, H, Clements, DL, Seager, S, Petkowski, JJ, Sousa-Silva, C, Ranjan, S, Drabek-Maunder, E, Fraser, HJ, Cartwright, A, Mueller-Wodarg, I, Zhan, Z, Friberg, P, Coulson, I, Lee, EL and Hoge, J (2020) Phosphine gas in the cloud decks of Venus. Nature Astronomy (2020) 1-10CrossRefGoogle Scholar
Jeans, J (1930) The Universe Around Us. Cambridge, UK: Cambridge University Press (Cambridge, England,UK), p. 343.Google Scholar
Lauro, SE, Pettinelli, E, Caprarelli, G, Guallini, L, Rossi, AP, Mattei, E, Cosciotti, B, Cicchetti, A, Soldovieri, F, Cartacci, M, Di Paolo, F, Noschese, R and Orosei, R (2020) Multiple subglacial water bodies below the south pole of Mars unveiled by new MARSIS data. Nature Astronomy 5, 63–70.CrossRefGoogle Scholar
Meadows, VS, Reinhard, CT, Arney, GN, Parenteau, MN, Schwieterman, EW, Domagal-Goldman, SD, Lincowski, AP, Stapelfeldt, KR, Rauer, H and DasSarma, S (2018) Exoplanet biosignatures: understanding oxygen as a biosignature in the context of its environment. Astrobiology 18, 630–662.CrossRefGoogle ScholarPubMed
NAS (2019) An Astrobiology Strategy for the Search for Life in the Universe. Washington, DC, USA: National Academies of Science Technology and Medicine.Google Scholar
Neveu, M, Hays, LE, Voytek, MA, New, MH and Schulte, MD (2018) The ladder of life detection. Astrobiology 18, 1375–1402.CrossRefGoogle ScholarPubMed
O'Hagan, A, Buck, CE, Daneshkhah, A, Eiser, JR, Garthwaite, PH, Jenkinson, DJ, Oakley, JE and Rakow, T (2006) Uncertain Judgements: Eliciting Experts' Probabilities. Chichester, West Sussex, England, UK: John Wiley & Sons.CrossRefGoogle Scholar
Oró, J (2002) Historical understanding of life's beginnings. Life's origin. In Schopf, JW (ed.), The Beginning of Biological Evolution. Berkeley, CA, USA: University of California Press, pp. 7–45.Google Scholar
Pohorille, A and Sokolowska, J (2020) Evaluating biosignatures for life detection. Astrobiology. https://doi.org/10.1089/ast.2019.2151CrossRefGoogle ScholarPubMed
Schwieterman, EW, Kiang, NY, Parenteau, MN, Harman, CE, DasSarma, S, Fisher, TM, Arney, GN, Hartnett, HE, Reinhard, CT and Olson, SL (2018) Exoplanet biosignatures: a review of remotely detectable signs of life. Astrobiology 18, 663–708.CrossRefGoogle ScholarPubMed
Seager, S and Bains, W (2015) The search for signs of life on exoplanets at the interface of chemistry and planetary science. Science Advances 1, e1500047.CrossRefGoogle Scholar
Seager, S, Schrenk, M and Bains, W (2012) An astrophysical view of Earth-based metabolic biosignature gases. Astrobiology 12, 61–82.CrossRefGoogle ScholarPubMed
Seager, S, Bains, W and Hu, R (2013) Biosignature gases in H2-dominated atmospheres on rocky exoplanets. The Astrophysical Journal 777, 95.CrossRefGoogle Scholar
Seager, S, Petkowski, JJ, Gao, P, Bains, W, Bryan, NC, Ranjan, S and Greaves, J (2020) The Venusian lower atmosphere haze as a depot for desiccated microbial life: a proposed life cycle for persistence of the Venusian aerial biosphere. Astrobiology. https://doi.org/10.1089/ast.2020.2244.CrossRefGoogle ScholarPubMed
Sousa-Silva, C, Seager, S, Ranjan, S, Petkowski, JJ, Zhan, Z, Hu, R and Bains, W (2020) Phosphine as a biosignature gas in exoplanet atmospheres. Astrobiology 20, 235–268.CrossRefGoogle ScholarPubMed
Walker, SI, Bains, W, Cronin, L, DasSarma, S, Danielache, S, Domagal-Goldman, S, Kacar, B, Kiang, NY, Lenardic, A and Reinhard, CT (2018) Exoplanet biosignatures: future directions. Astrobiology 18, 779–824.CrossRefGoogle ScholarPubMed
Supplementary material: PDF

Bains and Petkowski supplementary material

Appendices

Download Bains and Petkowski supplementary material(PDF)
PDF 523.2 KB