Research

Detection of molecular biosignatures on Mars

Current scientific support to martian space missions

One of the primary goals of current and future exploration missions to Mars concerns the search for traces of past or present life. In particular, detection of molecular biosignatures in the martian soil is highly desirable because they provide more directly observable evidence of biogenicity than other categories of biosignatures for which biological production is only inferred.

My work supports the scientific activities of space flight instruments devoted to detection of molecular biosignatures on board the ESA mission ExoMars 2022, and the NASA missions Mars 2020 and Mars Science Laboratory (MSL).

Specifically, main investigations pertain to:

    • Preparation of Mars soil analog samples by doping minerals relevant to martian mineralogy with organic compounds considered as plausible biomarkers;

    • Characterization of Mars soil analogs through various techniques, such as Fourier Transform InfraRed (FTIR) and Raman vibrational spectroscopies, UV-vis spectrophotometry, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis;

    • UV-irradiation processing of Mars soil analogs under Martian-like conditions, in order to develop models for molecular degradation in the martian geological record;

    • Detectability/sensitivity tests and combined science activities between space flight instruments like MicrOmega, Raman Laser Spectrometer (RLS) and Mars Organics Molecule Analyser (MOMA) on board ExoMars 2022, Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) and SuperCam on board Mars 2020, Sample Analysis at Mars (SAM) and CheMin on board MSL, in order to develop coordinated strategies for life detection;

Past activities: Development of liquid extraction protocols suitable for in situ biosensor-based instruments

My Master Thesis research focused on the development of liquid extraction protocols suitable for in situ biosensor-based instruments, evaluating the effect on the extraction efficiency of different solvent systems, heating and input of ultrasonic energy compatible with immunoassay. Such work supported the scientific activity of the instrument Life Marker Chip (LMC) initially selected for the ExoMars space mission, which is an antibody microarray biosensor instrument with optical readout that uses fluorescently labelled antibodies to detect and quantify polar and non-polar biomolecules extracted from soil.

Roles of minerals in the origin of life

Study of molecule-mineral interactions and binding mechanisms

Studies about interactions between organic matter and inorganic substrates allow us to address a fundamental question in Astrobiology concerning the crucial transition from geochemistry to biochemistry. This transition probably occurred through selection, concentration and organization of the organic precursors, yielding the essential macromolecules of life. Mineral surfaces might have played a very important role in such processes, due to their ability to selectively adsorb and concentrate organic molecules on a local scale, removing key organics from the aqueous environments where hydrolysis inhibits polymerization, promoting self-organization and catalyzing important chemical reactions. Therefore, the study of molecule-mineral interactions under plausible prebiotic and space conditions may be a step forward in resolving unsolved questions of the origins of life.

For characterization of mineral phases I employ X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis. In order to get insights into the specific molecule-mineral interactions, I use FTIR and Raman vibrational spectroscopies. Moreover, I examine the thermodynamics of the adsorption process both experimentally, determining equilibrium adsorption isotherms, and computationally through quantum mechanical and surface complexation modelling.

Computational Spectroscopy

Computational studies provide a tool to investigate intermolecular interactions playing a crucial role in self-assembling mechanisms of key molecules in the prebiotic context and their binding to mineral surfaces, which are of great interest to unravel the processes leading to the emergence of life on Earth or other planets. Moreover, accurate simulations of spectroscopic features assist the interpretation of rather intricate experimental/observational measurements, providing a support for in situ and remote sensing spectroscopy to detect biomarkers in space.

My PhD project dealt with computational spectroscopic studies of molecular systems relevant in Astrobiology. I developed comprehensive yet feasible quantum mechanical protocols for the characterization of spectroscopic properties of “building blocks of life” such as nucleic acid components adsorbed on mineral surfaces, by means of Density Functional Theory methods. Such in silico modelling turned out to be fundamental to dissect the contributions of different intra- and inter-molecular interactions to the overall spectroscopic signals.

PROSPECT

Studies of water sublimation from lunar samples to support PROSPECT space mission, which will operate at the surface of the Moon as part of the Russian-led Luna-27 mission in 2022.

For further info about research projects of the Arcetri Astrobiology Laboratory, please, visit our website: https://sites.google.com/inaf.it/arcetriastrobiologylaboratory/home