LIBS application for analyses of martian crust analogues:: search for the optimal experimental parameters in air and CO2 atmosphere

The optimal experimental conditions for quantitative analyses of the Martian similar crust by Laser Induced Breakdown Spectroscopy (LIBS) were studied comparatively in the air at atmospheric pressure and under the simulated planet atmosphere. Different laser energies were applied and the plasma dynamic, in terms of the emission intensity, temperature and electron density, were studied. The choice of the best experimental parameters includes: acquisition delay from the laser pulse and gate where the conditions of Local Thermal Equilibrium (LTE) holds, as necessary for the quantitative analyses, and further optimisation of the same parameters, as well as of the shot number, in order to maximize signal-to-noise ratio (S/N). Preliminary results demonstrate that for the same laser energies in a rarefied CO2 atmosphere the acquisition window where LTE conditions hold is much shorter than in the air due to the low electron density, fast plasma cooling and decay, where the last is the cause for even shorter optimum interval for maximizing S/N.