MSL DAN Passive Data and Interpretations

Christopher G Tate1, Jeffrey Moersch2, Insoo Jun3, Douglas W Ming4, Igor G. Mitrofanov5, Maxim L Litvak5, Alberto Behar6, William V Boynton7, Darrel Drake8, Denis Lisov5, Michael Mischna9, Craig J Hardgrove10, Ralph Milliken11, Anton B. Sanin5, Richard D Starr12, Javier Martín-Torres13, María-Paz Zorzano14, Fedor Fedosov5, Dmitry Golovin5, Karl Harshman7, Alexander Kozyrev5, Alexey V Malakhov5, Maxim Mokrousov5, Sergey Nikiforov5 and Aleksey Varenikov5, (1)University of Tennessee, Knoxville, TN, United States, (2)University of Tennessee, Department of Earth, Environmental, and Planetary Sciences, Knoxville, United States, (3)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (4)NASA Johnson Space Center, Houston, TX, United States, (5)Space Research Institute RAS, Moscow, Russia, (6)NASA Jet Propulsion Laboratory, (deceased), Pasadena, CA, United States, (7)University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ, United States, (8)TechSource, Inc, Los Alamos, NM, United States, (9)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States, (10)Arizona State University, Tempe, AZ, United States, (11)Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, United States, (12)Catholic University of America, Washington, DC, United States, (13)Instituto Andaluz de Ciencias de la Tierra, Granada, Spain, (14)INTA-CSIC, Madrid, Spain
Abstract:
In its passive mode of operation, The Mars Science Laboratory Dynamic Albedo of Neutrons experiment (DAN) detects low energy neutrons that are produced by two different sources on Mars. Neutrons are produced by the rover's Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) and by interactions of high energy galactic cosmic rays (GCR) within the atmosphere and regolith. As these neutrons propagate through the subsurface, their energies can be moderated by interactions with hydrogen nuclei. More hydrogen leads to greater moderation (thermalization) of the neutron population energies. The presence of high thermal neutron absorbing elements within the regolith also complicates the spectrum of the returning neutron population, as shown by Hardgrove et al. DAN measures the thermal and epithermal neutron populations leaking from the surface to infer the amount of water equivalent hydrogen (WEH) in the shallow regolith. Extensive modeling is performed using a Monte Carlo approach (MCNPX) to analyze DAN passive measurements at fixed locations and along rover traverse segments. DAN passive WEH estimates along Curiosity's traverse will be presented along with an analysis of trends in the data and a description of correlations between these results and the geologic characteristics of the surfaces traversed.
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