Stand-off detection and mapping of mineral and organic compounds using ultraviolet Raman spectroscopy

English Abstract:

Developments in ultraviolet lasers and imaging systems have resulted in the potential for a stand-off ultraviolet Raman instrument that is capable of detecting and identifying low concentrations of mineral and organic compounds in-situ in either terrestrial or planetary settings. An ultraviolet wavelength offers several advantages over visual or infrared excitations, including reduced fluorescence in the Raman window, improved sensitivity due to the increased Raman cross section, and resonance with some organics. A sub-nanosecond laser pulse permits gating of the detector to reject fluorescence, and using an intensified CCD can increase the Raman signal to noise ratio. We present a Raman instrument with an excitation wavelength of 266 nm intended for the detection of organic compounds on Mars, and demonstrate the potential of an ultraviolet Raman system for performing spatial mapping of mineral and organic compounds on a millimeter to centimeter scale. We demonstrate the ability to perform this mapping on a suite of unprepared sedimentary samples containing endoliths from the Canadian Arctic and the Atacama Desert, and show that uneven topography and impurity of the sample do not prevent the ability to obtain spatial maps of the primary mineral and organic components. An ultraviolet Raman instrument such as the one presented is a valuable tool for definitive identification of organics and for determining mineralogy rapidly and non-destructively on unprepared samples in the field or on planetary surfaces. This research was carried out at the Planetary Instrumentation Laboratory at York University, and supported in part by both the Canadian Space Agency (CSA) and by the Natural Sciences and Engineering Research Council of Canada (NSERC).