The potential of Raman spectroscopy for the analysis of diagenetically transformed carotenoids.

Recently, carotenoids have received much attention as target compounds for astrobiological prospecting principally because they are a group of molecules that display unique diagnostic Raman spectra that can be assigned to organic material of unequivocal biological origin. However, no work has been performed on assessing the potential of Raman spectroscopic detection of carotenoids from fossilized microbes. Here, we report the first Raman spectra acquired from 'perhydro' derivatives of beta-carotene and lycopene formed by hydrogenation of the polyene chain during diagenesis, resulting in much less specific fossil hydrocarbons such as beta-carotane and lycopane, respectively. We propose here that diagenetically altered carotenoids formed by hydrogenation reactions during the fossilization processes also provide unique diagnostic spectra that can be interpreted as a biological signature.