Download Raman spectroscopy for future planetary exploration: detection of

Raman spectroscopy for future planetary exploration: detection of microorganisms behind
minerals
“Is there life on other planets?” is one of the key questions in space exploration. The aim of this
research project is to search for a method which can detect molecules that indicates of life or
former life on different objects in our solar system (for example Mars). Raman spectroscopy is a
very strong analytical tool which provides us with molecular information of compounds. Every
compound has a unique signature, as in a fingerprint. Although the Raman effect is not very
strong, it is possible to selectively enhance the signals of selected compounds by using different
laser wavelengths (different colours) as light source.
Two different microorganisms were detected through translucent and transparent minerals using
440-nm excitation under resonance conditions to selectively enhance the detection of
carotenoids. The 3-picosecond laser pulses and 250-picosecond gated intensified CCD camera
provided depth selectivity for the subsurface microorganisms over the mineral surface layer, and
in addition lowered the contribution of the fluorescent background. Raman spectra of both
organisms could be detected through 5 mm of translucent calcite or 20 mm of transparent halite.
Multi-layered mineral samples were used to further test the applied method. One has to keep in
mind that photodegradation and self-absorption are competing processes under resonant
conditions.
With the results of this project we will be able to write a recommendation for the appropriate
equipment as well as an analytical protocol for future planetary missions of ESA.