Identifying biosignatures on Planetary Surfaces with Laser-based Mass Spectrometry

We present a Laser-based Mass Spectrometer (LIMS) for the sensitive, chemical (elements, isotopes, and molecules) analysis of matter as an analytical instrument on a landed spacecraft on planetary surfaces for the identification of signatures of life, extinct or extant. Our LIMS system is compact, features simple and robust operation, and is optimized for the detection of signatures of life, among others. The LIMS instrument can be part of the science payload on a rover or be part of an instrument suite on a landed spacecraft supplied by a common sample delivery system. The LIMS instrument is a reflectron-type time-of-flight mass spectrometer coupled to a pulsed laser system for the removal of material from solid samples for mass spectrometric analysis. Operating LIMS with high laser irradiances results in material ablation from the surface, which is used for element and isotope analysis. Moreover, when staying at the same spot the sequence of mass spectra resulting from these laser pulses can be used to derive a depth profile of the atomic composition at the sampled location, all the way to 3D composition analysis with high spatial resolution. Fossils embedded in a mineral host, as an example, can then be identified by their unique chemical signature compared to the host mineral(s), allowing us to study even single microbes. In addition, the measurement of isotope abundances, e.g. sulfur, provides additional information on biogenicity, the environment, and the metabolism of the life forms. Alternatively, operating LIMS with low laser irradiances results in gentle desorption of chemical compounds, which is used for the detection of molecules and biomolecules present on the investigated surface. We obtain chemical information of molecules present on a surface, with a sensitivity down to fmol / mm
²
, registering signals from intact complex molecules as well as their unique and simple fragment distribution, allowing for unambiguous chemical identification of the species. This allows for the study of biologically relevant complex molecules extracted from a surface sample, e.g. amino acids, lipids, polycyclic aromatic hydrocarbon, and other biomolecules with high sensitivity.