Investigation of Normalization Methods using Plasma Parameters for Laser Induced Breakdown Spectroscopy (LIBS) under simulated Martian Conditions

Laser Induced Breakdown Spectroscopy data need to be normalized, especially in the field of planetary exploration We investigated plasma parameters as temperature and electron density for this purpose

LIBS for prospecting and Raman spectroscopy for monitoring: two feasibility studies for supporting in-situ resource utilization

Laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy are still rather new techniques for in-situ exploration of extraterrestrial planetary surfaces but have shown their suitability and great potential in several successful robotic missions already. Next to serving primary scientific applications, both methods can also be used in the context of in-situ resource utilization (ISRU) such as scouting for wanted substances and the surveillance of extraction processes. Here, we present two laboratory studies conducted in the context of ISRU with a focus on the chain from prospecting to extracting oxygen from lunar regolith. For LIBS, with optimized data processing and combined with state-of-the-art multivariate data analysis approaches, we show the potential of the technique for identifying samples with increased ilmenite content and for elemental quantification. The measurements were done using lunar regolith simulant and low pressures simulating vacuum on atmosphereless bodies such as the Moon. With Raman spectroscopy, we analyzed lunar regolith simulant samples that underwent electrochemical alteration for oxygen extraction and production of metal alloys demonstrating the potential of Raman spectroscopy for ISRU process monitoring. We also discuss the results in a broader context, evaluating the potential of both methods for other aspects of ISRU support.Peer Reviewe

Molecular emission in laser-induced breakdown spectroscopy: An investigation of its suitability for chlorine quantification on Mars

The intensity of the molecular CaCl emission in LIBS spectra is examined in order to evaluate its suitability for the detection of chlorine in a Martian environment. Various mixtures resembling Martian targets with varying Cl content are investigated under simulated Martian conditions. The reactions leading to the formation of CaCl are modeled based on reaction kinetics and are used to fit the measured CaCl band intensities. MgCl bands are also investigated as potential alternatives to CaCl, but no MgCl bands can be identified in samples containing both Mg and Cl. The study confirms that CaCl is well suited for the indirect detection of chlorine, but finds a strong dependence on the concentrations of Ca and Cl in the sample. Spectra from samples with a high chlorine concentration can have low-intensity CaCl emission due to a deficiency of Ca. A qualitative estimate of the sample composition is possible based on the ratio of the band intensity of CaCl to the intensity of Ca emission lines. Time-resolved measurements show that the CaCl concentration in the plasma is highest after about 1 µs

CaCl and CaF emission in LIBS under simulated martian conditions

Chlorine and fluorine play an important role in the geological history of Mars due to their high concentration in Martian magmas and their influence on the generation and evolution of Martian basalts. Chlorine-bearing salts could also facilitate the formation of eutectic brines that could be important for the fluvial history of Mars. The LIBS instruments of ChemCam and SuperCam can detect emission lines of Cl and F, but the intensity of these emission lines is comparatively low, making it difficult to quantify them correctly. A promising alternative is the quantification by molecular emission of diatomic molecules like CaCl and CaF, which can be observed as intense molecular bands in LIBS spectra if Ca is also present. However, the nonlinear dependence of the band intensity on the concentrations of both elements needs to be considered. In this study, we expand upon our previous analysis of molecular bands by investigating samples which produce CaCl bands, CaF bands, or both. We find that the highest CaCl band intensities are found in samples containing more Ca than Cl, while the strongest CaF bands are found in samples with roughly equal concentrations of Ca and F. Both observations can be described by the model that we present here. We also find that the CaCl band is significantly stronger for a sample containing CaCl2 than it is for a sample containing the same concentrations of Ca and Cl in separate bonds. The opposite is true for the CaF band, which is significantly weaker for the sample containing CaF2 bonds than it is for the sample that does not contain CaF2 bonds. These matrix effects are partially attributed to fragmentation during the ablation process and differences in the dissociation energies. Furthermore, we observe that CaF formation is not affected by competing CaCl formation, while CaCl is strongly affected by competing CaF formation. All measurements are done in simulated Martian atmospheric conditions in order to assist the analysis of Martian LIBS data

Spectral investigation of volcanic alteration deposits on Vulcano island /Italy as planetary analog for acid alteration conditions on Mars

During the fifth International Summer School held on Vulcano (Eolian Islands, Italy) in June 2019 we started the investigation of volcanic deposits with different spectral instruments combining mineralogical, elemental and molecular information [1, 2]. The island of Vulcano presents an extremely large variety of volcanic products [3] in extreme acid alteration conditions. Acidic alteration may also have been a key process throughout Martian geologic history making Vulcano a perfect analog for studies on Mars by defining the geochemistry at these sites. In this work we present an update of our spectral investigations based on the VIS-NIR spectral measurements