Stand-off detection of amino acids and nucleic bases using a compact instrument as a tool for search for life

Abstract

Amino acids and nucleobases are of particular interest to NASA’s science goal of “Search for life” because they are essential for life as the basic constituents of proteins and deoxyribonucleic acids (DNA). Their detection would point to possible biosignatures and potential life bearing processes and thus there is a need for technologies capable of identifying them. Raman spectroscopy provides univocal and accurate chemical characterization of organic and inorganic compounds and can be used to detect biological materials and biomarkers in the context of planetary exploration. While micro-Raman systems are useful, a remote Raman instrument can increase the analysis area around a rover or lander. At the University of Hawai‘i we developed a portable, compact time-resolved remote-Raman instrument using a small 3” diameter mirror lens telescope, and used it to demonstrate daytime detection of amino acids and nucleobases from a distance of 8 m. The measured spectra allowed us to univocally identify 20 proteinogenic amino acids, four nucleobases, and some non-proteinogenic amino acids, despite the presence of native fluorescence, especially in aromatic compounds. We were also able to distinguish between α and β amino acids, as well as between different polymorphs. We found the remote Raman system is well suited for planetary exploration applications, with no requirement for sample preparation or collection, and rapid measurement times.