Planetary Surface Exploration

Faculty member Ralf Gellert is currently the lead scientist for the Alpha-Particle X-ray Spectrometer (APXS) on board the Mars Exploration Rovers (MER). Together with a team of scientists from the Max-Planck Institute in Mainz, the Jet Propulsion Lab and NASA we are performing the daily operations of the instruments on Mars and analyzing the returned data. The APXS is one of the analytical instruments mounted on the rover arm. It measures the chemical composition of rocks and soils with x-ray spectroscopy. Since the successful landing on Mars in January 2004 the rovers Spirit and Opportunity returned more than 100 APXS measurements from each site along their traverse of nearly 5 kilometers. Results of the APXS on both landing sites contributed to the findings of MER that water played a major role during the formation of the encountered rocks and soils. In collaboration with the group of Prof. Iain Campbell we are improving the theoretical model for the data analysis. The APXS uses alpha particles and x-rays from radioactive sources to excite characteristic elemental radiation. The GUPIX package for PIXE (Proton induced X-ray Emission) will be extended to include both of these excitation modes.


John L. (Iain) Campbell
Ralf Gellert
Joanne M. O'Meara