JPS Conf. Proc. 11, 040006 (2016) [6 pages]
Proceedings of International Symposium on Radiation Detectors and Their Uses (ISRD2016)
An Investigation of Elemental Composition of Martian Satellites by Gamma-ray and Neutron Spectrometer
1Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555, Japan
2School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan
3Geology Department, School of Education, Waseda University, Tokyo 169-8555, Japan
4School of Fundamental Science and Engineering, Waseda University, Tokyo 169-8555, Japan
5Department of Physics, University of Coimbra, 3004-516, Coimbra, Portugal
6CSIC- The Complutense University of Madrid, Madrid 28040, Spain
7Division of Earth and Planetary Materials Science, Tohoku University, Sendai 980-8576, Japan
8Department of Physics, Rikkyo University, Tokyo 171-8501, Japan
9Department of Chemistry, Tokyo Metropolitan University, Tokyo 192-0397, Japan
10The University Museum, The University of Tokyo, Tokyo 153-890, Japan
11Department of Earth and Planetary Sciences, The University of Tokyo, Tokyo 153-8902, Japan
12Japan Aerospace Exploration Agency, Kanagawa 252-5210, Japan
Received February 29, 2016

Japanese mission “Mars Moon eXploration (MMX)” which is currently at the planning stage will make close-up remote and in-situ observations of Phobos and Deimos, and return Phobos samples to Earth. The major scientific objectives of MMX are to characterize geochemical regions in their surface and to determine whether the origin of these Moons is of the captured asteroid or giant impact type. The MMX payload will include a Gamma-ray and Neutron Spectrometer (GNS), which will globally measure and map the surface elemental composition. The GNS consists of a Gamma-ray Sensor (GS) and a Neutron Sensor (NS). The GS consists of a High Purity Germanium (HPGe) detector with an excellent energy resolution as a main detector and a thin plastic scintillator surrounding the HPGe crystal as an anticoincidence detector. The HPGe crystal is cooled below 90 K by a compact mechanical cooler. The NS consists of a Li-glass scintillator to measure thermal neutrons, and a borated plastic scintillator to measure epithermal and fast neutrons. The GNS combines the distinct features of light weight, low power and excellent energy resolution. The GNS will allow to assess the global maps of such elements as H, O, Mg, Al, Si, S, K, Ca, Ti, Fe, Th, and U, depending on their concentrations in the Martian Moons. The high concentration of such volatile elements as H and S in their Moons, and low values of Ca/Fe and Si/Fe-ratios shows that they are solar system primordial bodies, while high values of Ca/F and Si/Fe-ratios and very low water concentration suggest the giant-impact origin. The GNS will allow disentangling weather the origin is captured asteroid or giant impact.

©2016 The Physical Society of Japan

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