DP15 - Analysis of plasma conditions in a simulated Martian atmosphere for the ExoMars mission

Kurzfassung

ExoMars, ESA`s next mission to Mars, will include a scientific instrument which combines Raman spectroscopy with Laser induced breakdown spectroscopy (LIBS) for the comprehensive in-situ mineralogical and elemental analyses of Martian rocks and soils. For the interpretation of the data, especially for the quantitative analysis, as well as for the developmentof the LIBS system it is crucial to understand the plasma conditions whichwill occur when measuring on Mars. We have studied these conditions inthe laboratory under simulated Martian atmospheric pressure, atmosphericcomposition and temperature, which can be generated in the dedicatedsample chamber of the instrument. The laser used for generating the LIBS plasma is similar to the one which is going to be used for the ExoMars mission. It is a diode pumped Nd:YAG laser which emits light pulses, with a duration of ~1.8 ns at 1064 nm. The pulse energy can be rgulated between0 and 3 mJ by a varable attenuator. The pulse has a Gaussian shape and creates a pit of 50µm diameter on the sample. The plasma emission is reflected by a torroid mirror into an Echelle spectrometer (Aryelle fromLasertechnik Berlin). The wavelength coverage is 279 - 900 nm and thespectral resolution is 14 - 96 pm depending on the wavelength. A gated ICCd (Andor) is used for recording the spectra. Martian analog materialssuch as Andesit (pressed ppowder) were used as samples. The plasma wasstudied in terms of emission intensity, termperature and electron density.Preliminary results show that in Martian environment the conditions of LocalThermal Equilibrium are more difficult to achieve than in air.