Application of Doehlert experimental design for the optimization of LIBS analysis in Martian conditions

摘要

Choosing a method of analysis to perform remote in situ analysis on Mars is no easy task. One method with great potential as a space exploration tool is Laser Induced Breakdown Spectroscopy (LIBS). LIBS has various advantages over more conventional methods such as alpha-X spectroscopy : 1) remote analysis up to 20 meters, 2) rapid analysis (few min), 3) detection of high and low Z elements including trace elements. LIBS is a well known analytical technique which has been applied on many types of samples such as liquids, solid samples in hostile environment and geological samples. Yet, its qualification as a reliable analysis tool on Mars surface sets a series of new challenges. A project called MALIS (Mars elemental Analysis by Laser Induced breakdown Spectroscopy) is under study to perform in situ geochemical analysis of Mars soils and rocks. To demonstrate the feasibility of LIBS in Martian conditions a better knowledge of the plasma emission is needed under Mars atmospheric conditions (Mars atmosphere is typically 5 - 12 mbar CO_2). Due to space limitations in terms of size, weight, and available power, it is important to characterize the method and to determine the best operating conditions to obtain in situ reliable analysis of Mars soils and rocks at stand of distance up to 20 meters. We use for the first time a Doehlert matrix design for LIBS optimization.