Circular Polarization in Scattered Light as a Possible Biomarker

Published

March 2, 2009

Author(s)

Thomas A. Germer, William Sparks, James H. Hough, Ludmilla Kolokolova, Feng Chen, Shiladitya DasSarma, Priya DasSarma, Frank Robb, Nadine Manset, Neill Reid, F. D. Macchetto, William Martin

Abstract

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 as a remote sensing biomarker.

Citation

Journal of Quantitative Spectroscopy and Radiative Transfer

Pub Type

Journals

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Keywords

astrobiology, chirality, circular dichroism, diffuse scattering

Citation

Germer, T. , Sparks, W. , Hough, J. , Kolokolova, L. , Chen, F. , DasSarma, S. , DasSarma, P. , Robb, F. , Manset, N. , Reid, N. , Macchetto, F. and Martin, W. (2009), Circular Polarization in Scattered Light as a Possible Biomarker, Journal of Quantitative Spectroscopy and Radiative Transfer, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=901371 (Accessed December 5, 2024)