Raman Spectroscopy

Abstract

The strategic adaptation of extremophiles (organisms which can survive where humans cannot) to survival in hostile terrestrial environments depends critically upon their synthesis of protectant biomolecules in geological niches to combat low wavelength radiation insolation, desiccation, and extremes of temperature and pH.

Each year sees the discovery of novel geological scenarios in which organisms have successfully created a tenacious colonisation in “limits of life” habitats. Terrestrial analogues such as hot and cold deserts, volcanoes and geothermal springs provide models for the extraterrestrial study of the evolution of life in our Solar System – astrobiology. In particular, the current robotic exploration of the surface and subsurface of Mars, our neighbouring planet which has held ancient magical significance for our ancestors and is still shrouded in mysteries, is now indicative of the importance of a range of terrestrial scenarios which can be considered as Mars analogues. The next phase of Martian exploration must address the robotic search for extinct or extant life in the geological record, which is essential for the proposed human missions in the next two decades. A key factor in the armoury of remote analytical instrumentation that is now envisaged for inclusion on extended-range Mars landers and rovers is the identification of the chemical and biochemical protectants that might have been produced by extremophiles for survival in the Martian deserts. The molecular signatures evidenced from the Raman spectra of these key protectants will be fundamental for the detection of biological activity on Mars and the adoption of miniaturised Raman spectrometers for Martian exploration is now being seriously considered by NASA and ESA. In this context, the evaluation of prototype Raman spectroscopic instrumentation for the detection of molecules of relevance to a wide range of terrestrial extremophilic activity is now being addressed and forms the subject of this article. Exemplars from various geological scenarios in the Arctic and Antarctic cold deserts and from relevant hot desert habitats, such as volcanic geothermal springs and salt pan evaporites, will reinforce the tenet of this book – that the molecular studies of extremophilic models will be pivotal in the understanding of the magic and mysteries of evolution of life on Earth and the search for life on Mars