Optimising Raman spectroscopic methods for the detection of past life signatures

The detection of current or past extra-terrestrial life remains a fundamental goal of planetary scientists. However, even on Earth finding unambiguous evidence of fossilised early life forms has proved extremely controversial due to the effects of impact and plate tectonic processes. Only the detection of diagnostic organic molecules (biomarkers) will provide definitive proof of past life on Mars and in Archaean rocks on Earth. Raman spectroscopy is an extremely specific technique (based on molecular vibrations) that is widely used in the Earth, life and chemical sciences to characterize materials in situ. Currently planned planetary missions will be carrying a Raman instrument that was designed for ruggedness, low weight and low power consumption. Its characteristics seem excellent for mineralogical studies, but may not be ideal for detecting trace amounts of organic biomarkers. We propose to optimise Raman spectroscopic conditions for the detection of biomarkers in rocks from the early Earth, with the ultimate goal to contribute to future Mars missions. Specifically, we will examine detection capabilities at different laser wavelengths and the viability of Raman under resonance conditions for improved selectivity. We plan to include laser modalities that are currently not sufficiently well developed for space applications, but for which the history of recent technical development suggests that they may soon become suitable for interplanetary missions. The interdisciplinary team includes international experts in Raman spectroscopy, coupled with biologists and Earth scientists currently examining life forms in extreme and early environments on Earth.