Simulations of Rover Based Neutron Remote Sensing of Periglacial Features on Mars

Introduction: Results from Mars Odyssey's highenergy neutron spectrometer, and gamma ray spectrometer have shown that there is 15 to 20% ice in the top meter of Martian regolith at latitudes of +/-55 degrees [1,2,3]. This observation has been critical in understanding the nature of patterned ground on Mars [4]. The resolution of the ground ice maps generated from these instruments, however, is approximately 600 kilometers per pixel, which does not allow the details of specific patterned ground features such as iceor sand-wedge polygonal cracks to be detected. One way to drastically improve the spatial resolution of neutron spectrometer measurements is to bring the detector to the surface. Many future rover missions, such as the 2009 Mars Science Laboratory, will include neutron spectrometers as part of their instrument suite. By acquiring data along traverses during normal mission operations, a rover-borne neutron spectrometer can generate high-resolution hydrogen maps of the local subsurface. Our goal is to show that local subsurface enrichments or depletions of hydrogen can be detected and that, in the case of polygonal cracks, the observed hydrogen content can be used to suggest a method of formation. In addition, knowledge of the present ice content in the cracks may provide clues about the past Martian climate and ground-ice abundance. Here we present the preliminary results of our study to determine the suitability of a rover-borne neutron detector for studying the structure and composition of polygonal cracks. We have simulated a neutron detector’s traverse across several uniform-composition cracks of fixed dimensions. The specific instrument modeled is a prototype neutron detector built under the Mars Instrument Development Program. A description of the electronics and operation of the detector has been described in several sources [5, 6]. Field tests with the detector will also be described in Piatek et. al [7].