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A Spectroscopic Polarimeter For Detecting Chiral Signatures In Astrobiological Samples

Published

Author(s)

Baoliang Wang, William Sparks, Thomas A. Germer, Andy Leadbetter

Abstract

We have developed a polarimeter for accurately measuring both the circular and linear polarization components of a light beam from 400 nm to 800 nm. This polarimeter is designed to work at low light levels that are typical in astronomical applications. It is optimized to detect the circular polarization signal that is orders of magnitude weaker than the linear polarization signal. Two photoelastic modulators (PEMs) are the key polarization components employed in this polarimeter to afford the high sensitivity required for the application. Using this polarimeter, we have quantified the circular polarization signal produced by astrobiologically relevant microorganisms and compared the results to macroscopic vegetation (such as leaves) and abiotic minerals. Our aim is to understand whether circular polarization offers a viable technique for remote detection of chiral signatures and hence will be useful as an element of telescopic searches for life elsewhere in the Universe. We see unambiguous circular polarization from photosynthetic microbes. The circular polarization of reflected light is related to the circular dichroism of the photosynthetic molecules. Therefore, circular polarization spectroscopy offers the prospect of remotely sensing life’s unique chiral signature.
Proceedings Title
Instruments, Methods, and Missions for Astrobiology XII (Proceedings of SPIE, Vol. 7441B)
Volume
7441
Conference Dates
August 4-6, 2009
Conference Location
San Diego, CA

Keywords

astrobiology, chiral signature, circular polarimeter, homochirality, photoelastic modulator, polarization modulation, polarization spectroscopy, spectropolarimetry, Stokes polarimeter

Citation

Wang, B. , Sparks, W. , Germer, T. and Leadbetter, A. (2009), A Spectroscopic Polarimeter For Detecting Chiral Signatures In Astrobiological Samples, Instruments, Methods, and Missions for Astrobiology XII (Proceedings of SPIE, Vol. 7441B), San Diego, CA (Accessed August 1, 2021)
Created September 11, 2009, Updated February 19, 2017