A suite of spectroscopic devices as a potential tool to discriminate biotic and abiotic materials with an igneous rock

Spectroscopic technologies are prominent tools for the detection of potential extraterrestrial chemical bio-markers, such as those on Mars. However, the biomass in Martian samples, if existed, is expected to be extremely low, so it is crucial to understand the low boundary of spectroscopic detections. In this study, a Martian basalts-like igneous rock and four representative bacterial strains were used to examine the biomarker detection po-tentials of the laser-induced breakdown (LIBS), Raman, infrared (IR), and X-ray spectroscopies. A series of concentration gradients of these strains were prepared and dropped onto the basaltic sample, the areas of which were then analyzed by spectrometers. The multivariate analysis of LIBS data can differentiate areas with several to tens of cells per cm2 from basaltic components. In addition, Raman and Fourier-transform IR (FTIR) spec-trometers are robust to detecting organic chemical bonds or biological materials when cells are directly targeted. If more water-rich conditions are present, LIBS, Raman, and FTIR spectrometers were all able to acquire this more habitable information. Moreover, transmission electron microscopy (TEM) and affiliated energy dispersive X-ray spectroscopy (EDS) can examine the microscale shapes and chemical distribution within suspicious compartment structures. These findings imply that LIBS-associated statistics and suites of spectrometers can be promising tools for in situ life detection on Mars or returned sample analyses in laboratories if biotic materials were present in a small measured region even at low biomass levels.