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Surface and Temporal Biosignatures

  • Edward W. SchwietermanEmail author
Living reference work entry

Abstract

Recent discoveries of potentially habitable exoplanets have ignited the prospect of spectroscopic investigations of exoplanet surfaces and atmospheres for signs of life. This chapter provides an overview of potential surface and temporal exoplanet biosignatures, reviewing Earth analogues and proposed applications based on observations and models. The vegetation red-edge (VRE) remains the most well-studied surface biosignature. Extensions of the VRE, spectral “edges” produced in part by photosynthetic or nonphotosynthetic pigments, may likewise present potential evidence of life. Polarization signatures have the capacity to discriminate between biotic and abiotic “edge” features in the face of false positives from bandgap-generating material. Temporal biosignatures – modulations in measurable quantities such as gas abundances (e.g., CO2), surface features, or emission of light (e.g., fluorescence, bioluminescence) that can be directly linked to the actions of a biosphere – are in general less well studied than surface or gaseous biosignatures. However, remote observations of Earth’s biosphere nonetheless provide proofs of concept for these techniques and are reviewed here. Surface and temporal biosignatures provide complementary information to gaseous biosignatures and, while likely more challenging to observe, would contribute information inaccessible from study of the time-averaged atmospheric composition alone.

Notes

Acknowledgments

The author gratefully acknowledges support from the NASA Astrobiology Institute and the NASA Postdoctoral Program administered by the Universities Space Research Association. The author also appreciatively acknowledges support from and access to tools developed by the NAI Virtual Planetary Laboratory under Cooperative Agreement Number NNA13AA93A. This chapter was improved by helpful comments from Kim Bott and Victoria Meadows.

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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.University of California, RiversideRiversideUSA

Section editors and affiliations

  • Victoria Meadows
    • 1
  • Rory Barnes
    • 2
  1. 1.Astronomy DepartmentUniversity of WashingtonSeattleUSA
  2. 2.Astronomy DepartmentUniversity of WashingtonSeattleUSA

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