Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso


  • John Lee Grenfell
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_5282-2


In exoplanet science the term “bioindicator” refers to an indication (or “hint”) that life as we know it could be present – but in order to decide more definitively would require additional information.


The detection, e.g., of atmospheric methane in an exoplanetary atmosphere would constitute a bioindicator because additional information is needed in order to determine whether or not the source is biological. This, in the case of methane, can be tested, e.g., by comparing the ratio of its outgassing amount with other outgassed species such as H2 (see, e.g., Oze et al. 2012) and/or by determining the carbon isotope ratio (as discussed in the review of Etiope and Sherwood Lollar 2013). In contrast, the term “biosignature” refers to a robust signal that is strongly suggestive of life. For example, the atmospheric detection of an Earth-like amount of nitrous oxide (N2O) for an Earth-like planet orbiting a sunlike star would constitute a biosignature because according...


Isotope Ratio Nitrous Oxide Carbon Isotope Carbon Isotope Ratio Atmospheric Methane 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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References and Further Reading

  1. Etiope G, Sherwood Lollar B (2013) Abiotic methane on Earth. Rev Geophys 51(2):276–299ADSCrossRefGoogle Scholar
  2. Hewitt CN, Jackson AV (eds) (2009) Atmospheric science for environmental scientists. Wiley-Blackwell, Oxford, p 105Google Scholar
  3. Kaiser J, Röckmann T (2005) Absence of isotope exchange in the reaction of N2O + O(1D) and the global 17O budget of nitrous oxide. Geophys Res Lett 32:LI15808ADSCrossRefGoogle Scholar
  4. Oze C, Jones C, Goldsmith JI, Rosenbauer RJ (2012) Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces. Proc Natl Acad Sci U S A 109:E3211ADSCrossRefGoogle Scholar
  5. Selsis F, Despois D, Parisot J-P (2002) Parisot, signature of life on exoplanets: can Darwin produce false positive detections? Astron Astrophys 388:985–1003ADSCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Institut für Planetenforschung, Extrasolare Planeten und AtmosphärenDeutsches Zentrum für Luft- und Raumfahrt (DLR)BerlinGermany