Modeling of a LIBS plasma emitted by organic components under Martian conditions with the aim of search for life in Mars

Abstract

This thesis focuses on modeling Laser-Induced Breakdown Spectroscopy (LIBS) plasma under Martian conditions. The theoretical framework investigates the interaction of nanosecond laser pulses with a solid organic target (graphite) in a Martian-like environment, specifically involving carbon dioxide (CO2) and helium (He) gases. A three-temperature (3T) Eulerian radiation model incorporating non-local thermodynamic equilibrium (NLTE) conditions is employed to capture the complex plasma dynamics during LIBS, taking into account the mixing between the expanding plasma plume and the surrounding gas. The study aims to provide a detailed understanding of laser ablation and plasma formation, with particular attention to the effects of laser irradiance and ambient gas pressure. The laser parameters used in the model replicate those of the ChemCam and SuperCam instruments. The work is limited to single-pulse excitation; post-ablation cavity effects are therefore not considered. Additionally, the thesis examines the impact of laser focusing conditions and ambient pressure ranging from 3 to 9 mbar (representative of Martian conditions) and up to 1000 mbar (Earth-like conditions) on key plasma parameters. The analysis is based on high-fidelity simulations performed using the open-source radiation-hydrodynamics code FLASH, which was used to calculate electron and ion temperatures, electron and ion number densities, and fluid velocities within the plasma.