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3 September 2009 A spectroscopic polarimeter for detecting chiral signatures in astrobiological samples
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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 instrument, 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 photosynthetic molecules. Therefore, circular polarization spectroscopy offers the prospect of remotely sensing life's unique chiral signature.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Baoliang Wang, William B. Sparks, Thomas A. Germer, and Andrew Leadbetter "A spectroscopic polarimeter for detecting chiral signatures in astrobiological samples", Proc. SPIE 7441, Instruments and Methods for Astrobiology and Planetary Missions XII, 744108 (3 September 2009);


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