Sulfur Observations and Analysis by the Alpha Particle X-ray Spectrometer and ChemCam Instruments on the Mars Science Laboratory Rover
The ChemCam and APXS instruments on the Mars Science Laboratory rover are used for geochemical investigations. The instruments use LIBS and X-ray spectroscopy, respectively. The detection of sulfur is considered important because its presence can help reveal details about the past environment on Mars. The APXS regularly detects and reports sulfur, while low signal and high detection limits cause difficulties for sulfur quantification with ChemCam. In this work, the limitations and obstacles of studying sulfur with LIBS are addressed by examining both laboratory and mission results. A univariate method is developed using the summation of the 564nm sulfur peak after a background subtraction. This robust approach was used to estimate a calibration between the sulfur peak and sulfur content of the sample. Ultimately, this work outlines and describes the many intricacies of using LIBS as a remote geochemical analysis tool, specifically the obstacles involved in quantifying sulfur with the ChemCam.