PING INSTRUMENT GAMMA-RAY DATA ANALYSIS OF PLANETARY ANALOGS

The Probing In situ with Neutrons and Gamma rays (PING) instrument is capable of performing detailed bulk geochemical analysis in situ 30-50 cm into the subsurface of planetary bodies without the need to take a soil sample. Neutrons emitted by the pulsed neutron generator (PNG) interact with the nuclei in the soil, causing the nuclei to emit gamma rays whose energies are specific to the nuclei that emitted them. These gamma rays are detected and their rate and energy are measured by a gamma-ray spectrometer. Numerical gamma-ray data returned by PING are summed and made into a graphical representation of the spectrum as energy vs. gamma-ray count using Igor Pro 6. The data are then run through custom software procedures that allow for easy calibration and spectral analysis. Each energy peak in the gamma-ray spectra represents the presence of a unique isotope while the area underneath each peak represents the gamma-ray count rate, which can be converted to a weight percent of that isotope in the material. Various configurations using Columbia River Basalt, Concord Gray Granite, and polyethylene plates are used as planetary analogs in experiments designed to test PING. The gamma-ray spectra corresponding to these experiments are analyzed by finding the locations of the energy peaks and determining their area by using peak-fitting methods in Igor Pro 6. In this analysis, advanced error reduction methods are applied in order to retrieve the most accurate data possible from each peak in the spectra. Future work includes comparison to chemical assays of the analogs, which will be performed by other members of the group.