Destruction of Raman biosignatures by ionising radiation and the implications for life detection on Mars

Dartnell, L. R., Page, K., Jorge-Villar, S. E. , Wright, G., Munshi, T., Scowen, I. J., Ward, J. M. and Edwards, H. G. M. (2012) Destruction of Raman biosignatures by ionising radiation and the implications for life detection on Mars. Analytical and Bioanalytical Chemistry, 403 (1). pp. 131-144. ISSN 1618-2642

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Raman spectroscopy has proven to be a very effective approach for the detection of microorganisms colonising hostile environments on Earth. The ExoMars rover, due for launch in 2018, will carry a Raman laser spectrometer to analyse samples of the martian subsurface collected by the probe's 2-m drill in a search for similar biosignatures. The martian surface is unprotected from the flux of cosmic rays, an ionising radiation field that will degrade organic molecules and so diminish and distort the detectable Raman signature of potential martian microbial life. This study employs Raman spectroscopy to analyse samples of two model organisms, the cyanobacterium Synechocystis sp. PCC 6803 and the extremely radiation resistant polyextremophile Deinococcus radiodurans, that have been exposed to increasing doses of ionising radiation. The three most prominent peaks in the Raman spectra are from cellular carotenoids: deinoxanthin in D. radiodurans and β-carotene in Synechocystis. The degradative effect of ionising radiation is clearly seen, with significant diminishment of carotenoid spectral peak heights after 15 kGy and complete erasure of Raman biosignatures by 150 kGy of ionising radiation. The Raman signal of carotenoid in D. radiodurans diminishes more rapidly than that of Synechocystis, believed to be due to deinoxanthin acting as a superior scavenger of radiolytically produced reactive oxygen species, and so being destroyed more quickly than the less efficient antioxidant β-carotene. This study highlights the necessity for further experimental work on the manner and rate of degradation of Raman biosignatures by ionising radiation, as this is of prime importance for the successful detection of microbial life in the martian near subsurface. © 2012 Springer-Verlag.

Keywords:Biosignatures, Cosmic rays (UHECRs), Cyanobacterium synechocystis, Deinococcus radiodurans, Exomars rovers, Hostile environments, Life detection, Mars, Martian surface, Microbe, Microbial life, Model organisms, Organic molecules, Radiation resistant, Raman lasers, Raman signal, Raman signatures, Reactive oxygen species, Spectral peak, Synechocystis, Astrobiology, Cosmic rays, Microorganisms, Ocean habitats, Pigments, Raman scattering, Raman spectroscopy, Ionizing radiation, article, astronomy, Deinococcus, ionizing radiation, isolation and purification, life, methodology, Raman spectrometry, Synechocystis, Deinococcus, Radiation, Ionizing, Spectrum Analysis, Raman, Synechocystis, Deinococcus radiodurans, Synechocystis, Synechocystis sp., Synechocystis sp. PCC 6803
Subjects:F Physical Sciences > F100 Chemistry
Divisions:College of Science > School of Chemistry
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ID Code:13018
Deposited On:19 Mar 2014 19:16

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