Application of optical photothermal infrared spectroscopy (O-PTIR) for future returned Mars samples.

Optical photothermal infrared spectroscopy (O-PTIR) was used to characterize a terrestrial rock sample as a demonstration of the technique's enhanced spatial resolution as it corresponds to minerology and the detection of organics. Traditional reflectance-based infrared techniques are limited by the wavelength of the infrared light interacting with the surface along with additional optical dispersion issues. However, because of the nature in which the infrared spectrum is measured via O-PTIR, these traditional issues are eliminated. This is possible through the recent developments of high intensity quantum cascade-based infrared lasers capable of scanning the mid infrared spectrum (3000-500 cm-1). Individual O-PTIR and diffuse reflectance data were collected on a terrestrial rock sample and compared to a recent discovery of NASA JPL's Perseverance Rover regarding inclusions of comparable size. In addition, an O-PTIR map of a particularly dense area of proteinaceous material in the terrestrial sample was collected, further exemplifying the capability. This technique has significant potential for use regarding future returned Mars samples and in situ planetary surface science when considering the spatial resolution, sensitivity, and negligible sample preparation.