Circular polarization in scattered light as a possible biomarker

By W. Sparks, James Hough, L. Kolokolova, T. Germer, Feng Chen, S. DasSarma, P. DasSarma, F. Robb, N. Manset, I. Neill Reid and 2 more. 2009

88 citations recorded by the source corpus.

Biological molecules exhibit homochirality and are optically active. Therefore, it is possible that the scattering of light by biological molecules might result in a macroscopic signature in the form of circular polarization. If this is the case, then circular polarization spectroscopy, which may be utilized in remote sensing, can offer a powerful indicator of the presence of a universal biosignature, namely homochirality. Here, we describe laboratory experiments designed to investigate this idea. We focus on photosynthetic microorganisms, and also show results from macroscopic vegetation and control minerals. In the microorganisms, we find unambiguous circular polarization associated with electronic absorption bands of the photosynthetic apparatus. Macroscopic vegetation yields a stronger and more complex signature while the control minerals produce low-levels of circular polarization unrelated to their spectra. We propose a heuristic explanation of our results, which is that the polarization is produced by circular dichroism in the material after the light has undergone its last scattering event. The results are encouraging for the use of circular polarization spectroscopy in remote sensing of a generic biomarker from space or the ground.

Subfields: Astronomy and Astrophysics, Cellular and Molecular Neuroscience, Plant Science

View Paper: https://www.semanticscholar.org/paper/f7aec83e28f8939875491ee95806d3620ef56be4

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In Astronomy and Astrophysics

1. E. Schwieterman
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3. J. Grenfell
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5. R. Hu

Citations in the corpus

• Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life (2017, background): “However, of concern is the relatively weak signal strength of the circular polarization signal of photosynthetic pigments, which is on the scale of 10-2–10-4 (Sparks et al., 2009a, 2009b).”