Evaluation of miniaturized Raman spectrometers for planetary exploration: From aromatics to amino acids

Abstract

Organic molecules are currently believed to be abundant in space, but the possible biogenic origin, or the mere existence, on some planetary surfaces, Mars specifically, is a pending question. Reliable methods of detection are required to answer this question unambiguously and Raman spectroscopy has already been suggested for this task years ago. With exploration missions aiming to Mars on the horizon, collecting experience and building databases will have crucial importance investigations of analytical data obtained through Raman instrumentation onboard of rovers in the frame of Mars 2020 and other forthcoming missions. This work focuses on the evaluation of some portable Raman systems coupled to different excitation lasers (532, 785, 1064 nm and a dual laser system with sequentially shifted excitation SSE) for the detection of various organic molecules, with emphasis on non-complicated measure protocol and observation of fluorescence emission when a different wavelength is used. By using a simple statistical approach, we demonstrate a generally good readability of the obtained spectra for most of the investigated organics regardless the excitation sources and instruments used. A varying level of fluorescence emission was encountered, resulting in higher background for the 532 nm and 785 nm instrumentation while 1064 nm and SSE spectrometers provided almost fluorescence-free spectra. These results illustrate how the relatively simple miniaturized Raman spectrometers can provide fast and unambiguous identification of various organic compounds which are of great importance in the current and future planetology and/or exobiology missions.