Publication
Reference
Poch O., Frey J., Roditi I., Pommerol A., Jost B., Thomas N. (2017). Remote Sensing of Potential Biosignatures from Rocky, Liquid, or Icy (Exo)Planetary Surfaces. Astrobiology, 17, 231 - 252.
Names
  • O. Poch
  • J. Frey
  • I. Roditi
  • A. Pommerol
  • B. Jost
  • N. Thomas
Article and keywords
Title
Remote Sensing of Potential Biosignatures from Rocky, Liquid, or Icy (Exo)Planetary Surfaces
Abstract
To detect signs of life by remote sensing on objects of our Solar System and on exoplanets, the characterization of light scattered by surface life material could complement possible clues given by the atmospheric composition. We reviewed the reflectance spectra of a broad selection of major biomolecules that constitute terrestrial carbon-based life from 0.4 to 2.4 μm, and we discuss their detectability through atmospheric spectral windows. Biomolecule features in the near-infrared (0.8–2.4 μm) will likely be obscured by water spectral features and some atmospheric gases. The visible range (0.4–0.8 μm), including the strong spectral features of pigments, is the most favorable. We investigated the detectability of a pigmented microorganism (Deinococcus radiodurans) when mixed with silica sand, liquid water, and water-ice particles representative of diverse surfaces of potentially habitable worlds. We measured the visible to near-infrared reflectance spectra (0.4–2.4 μm) and the visible phase curves (at 0.45 and 0.75 μm) of the mixtures to assess how the surface medium and the viewing geometry affect the detectability of the microorganisms. The results show that ice appears to be the most favorable medium for the detection of pigments. Water ice is bright and featureless from 0.4 to 0.8 μm, allowing the absorption of any pigment present in the ice to be well noticeable. We found that the visible phase curve of water ice is the most strongly affected by the presence of pigments, with variations of the spectral slope by more than a factor of 3 with phase angles. Finally, we show that the sublimation of the ice results in the concentration of the biological material onto the surface and the consequent increase of its signal. These results have applications to the search for life on icy worlds, such as Europa or Enceladus.
Keywords
spectroscopy, grating spectrometer, photometry, gonio radiometer, bidirectional reflection, bidirectional reflectance spectra, visible, near-IR, molecular solid, organic matter, ice, water ice, biosignatures, biomolecules, pigments, proteins, DNA, phospholipids, carbohydrates, bacteria, Deinococcus radiodurans, Solar System
Content
BRDF data, material-matter, species, planetary sciences, earth sciences, chemistry, remote sensing
Year
2017
Journal
Astrobiology
Volume
17
Number
3
Pages
231 - 252
Document type
article
Publication state
published
Comments
None
Doi
10.1089/ast.2016.1523
Identifiers
Experiment/Spectra