Detection of pigments of halophilic endoliths from gypsum: Raman portable instrument and European Space Agency's prototype analysis

Abstract

A prototype instrument, under development at the University of Leicester, for the future European Space Agency (ESA) ExoMars mission, was used for the analysis of microbial pigments within a stratified gypsum crust from a hypersaline saltern evaporation pond at Eilat (Israel). Additionally, the same samples were analysed using a miniaturized Raman spectrometer, featuring the same 532 nm excitation. The differences in the position of the specific bands, attributed to carotenoid pigments from different coloured layers, were minor when analysed by the ESA prototype instrument; therefore, making it difficult to distinguish among the different pigments. The portable Delta Nu Advantage instrument allowed for the discrimination of microbial carotenoids from the orange/green and purple layers. The purpose of this study was to complement previous laboratory results with new data and experience with portable or handheld Raman systems, even with a dedicated prototype Raman system for the exploration of Mars. The latter is equipped with an excitation wavelength falling within the carotenoid polyene resonance region. The ESA prototype Raman instrument detected the carotenoid pigments (biomarkers) with ease, although further detailed distinctions among them were not achieved.

Discovery of carotenoid red-shift in endolithic cyanobacteria from the Atacama Desert

“…The Raman shifts of the ν 1 (C=C) carotenoid band positions obtained on these colonized layers of different coloration (orange, green, red) were documented by Culka et al . 44 . However, the individual layers are occupied by a distinct genus of cyanobacteria in the solar salterns, and the character of the ecosystem studied here is different.…”

Raman spectroscopy on Mars: identification of geological and bio-geological signatures in Martian analogues using miniaturized Raman spectrometers

“…One example is stratified gypsum crust extracted from a hypersaline saltern evaporation pond in Eilat, Israel (see [39] in this volume for example spectra from these samples). The gypsum crust was found to contain microbial pigment, apparent in the form of three different coloured layers.…”

“…Raman bands between 1000 and 1515 cm −1 ). Noting that, the wavenumber differences expected for each of the different colours is expected to be between 1 and 5 cm −1 based on laboratory studies [39].…”

Obtaining Raman spectra of minerals and carbonaceous matter using a portable sequentially shifted excitation Raman spectrometer – a few examples

“…Portable Raman instruments are nowadays considered as useful tools for identifying minerals, microbiological pigments, as well as pigments used in different art disciplines . The use of transportable and portable Raman spectrometers in different disciplines was recently reviewed by Colomban and Vandenabeele et al ., and critical aspects adressed as well .…”

“…The portable, handheld and palm‐size systems can also be used in geobiology, microbiology areas to search for Raman spectroscopic signals of biosignatures . Those studies are more or less directly relevant for the next exobiology missions planned by NASA and ESA in the frame of next missions to Mars.…”