Quantification of Light Elements by the Mars Science Laboratory's Alpha Particle X-ray Spectrometer using Absolute Rayleigh Scatter Peak Analysis
The Mars Science Laboratory’s Alpha Particle X-ray Spectrometer (APXS) performs bulk-chemistry analyses on the surface of Mars. It is capable of quantifying elements Z>10 through its primary mechanisms of X-Ray Fluorescence and Particle Induced X-ray Emission. The APXS is indirectly able to quantify "invisible" light elements with atomic number Z<11, such as water or carbonates which cannot be detected. Traditional means for quantifying invisible elements make use of APXS scatter peaks by analyzing relative intensities of measured Compton and Rayleigh X-ray peaks. The work presented in this thesis approaches the quantification of invisibles by making analytical predictions of scatter peaks on an absolute scale, rather than relative. This allows one to use Rayleigh absolute scatter peaks as a measure of distance, while simultaneously determining invisibles. The method has also extended previous work by incorporating invisibles into the compositional matrix to iteratively determine concentrations in the presence of invisibles.