Feasibility study of rock identification at the surface of Mars by remote laser-induced breakdown spectroscopy and three chemometric methods

Abstract

The ChemCam instrument that will equip the Mars Science Laboratory (MSL) rover uses laserinduced breakdown spectroscopy (LIBS) to remotely identify Martian rocks in the proximity of the rover, and to quantitatively assess their composition. Sample identification is then the first step of the chemical analysis, as a decision aid for monitoring the rover and/or before a subsequent composition measurement. In this paper we analyze our experimental spectra obtained in the laboratory by three chemometric methods-principal components analysis (PCA), soft independent modeling of class analogy (SIMCA) and partial least-squares discriminant analysis (PLS-DA)-to investigate the feasibility of rocks classification by remote LIBS. If PCA is very interesting for data visualization, SIMCA and PLS-DA enable the making of automatic predictions. We show that SIMCA is less sensitive than PLS-DA, but also more robust when it encounters spectra of an unknown rock. The instrument accuracy during MSL operations will benefit from a combination of the two approaches.

Differentiation of fibrotic liver tissue using laser-induced breakdown spectroscopy

“…PC are typically displayed in a score plot where samples with similar characteristics form clusters [36]. Figure 5 shows the plot of PCA scores for the first two principal components covering the 61.9% and 26.0% of the total variance of the system.…”

Evaluation of supervised chemometric methods for sample classification by Laser Induced Breakdown Spectroscopy

“…However, SIMCA model is based on PCA, which defines the directions of maximum variance instead of finding directions that separate classes as in the case of PLS-DA. SIMCA was the first class modeling technique introduced in chemistry and nowadays it is one the best-known modeling classification methods and has been widely applied to spectroscopic techniques such as LIBS [15,17,20]. …”

“…Furthermore, the model must be able to classify a sample that does not belong to any Chemometrics and Intelligent Laboratory Systems 146 (2015) 354-364 class as unassigned and not classify it as another class (high robustness). Different chemometric methods have been employed in LIBS data analysis to perform reliable classification for various types of samples [14][15][16][17][18], even at remote sites such as rock classification on Mars. However, none of these works includes a complete analysis of the performance of these methods evaluating sensibility, generalization ability and robustness with very similar samples.…”

Homogeneity testing and quantitative analysis of manganese (Mn) in vitrified Mn-doped glasses by laser-induced breakdown spectroscopy (LIBS)

“…Laser Induced Breakdown Spectroscopy (LIBS) as an analytical technique has grown spectacularly in the past few years to the extent that it is now being used even in remote analysis in the Mars mission confirming its experimental maturity. [2][3][4][5][6][7][8][9] The concept of LIBS relates to the interaction of a focused high power laser beam with matter, inducing the plasma on the surface of the matter and recording the atomic emission spectra from the plasma. The irradiation with high power laser pulses (usually nanosecond time scale) leads to material ablation and formation of plasma.…”