We are developing the Moon Moisture Targeting Observatory (MoMoTarO), a radiation monitor of neutrons and gamma rays to search for water resources on the Moon. As fast neutrons travel through the lunar soil, they are scattered by light elements such as hydrogen in water, losing their energy, and becoming thermal and epi-thermal neutrons. The non-contact water exploration without excavation can be realized by measuring the difference in the number of thermal or epi-thermal neutrons depending on water content. The MoMoTarO project can also aim at fundamental scientific studies such as gamma-ray burst observations and the neutron lifetime mystery. We are now constructing an engineering model and demonstrating the performance of the MoMoTarO detector.

Water on the Moon has received increasing attention due to its importance in planetary science and the utilization of space resources. Future lunar rover missions are poised to conduct explorations, specifically focusing on locating water. Neutron spectroscopy is a powerful technique for estimating subsurface water content. In this study, lunar surface neutrons induced by galactic cosmic rays were investigated through Monte Carlo simulation. This effort aims to yield insights pertinent to in-situ water search explorations utilizing neutron spectrometers. The sensitivity of the leakage neutron intensity to the depth profile of subsurface water within the top 1.5 m soil was obtained via calculations based on a lunar surface model, featuring a localized concentration of water-rich soil. Computational outcomes underscore the potential of neutron observations to provide data on the depth profile of subsurface water under specific circumstances. Notably, in scenarios where a thin and shallow water-rich layer, approximately less than or similar to 20 cm thick and located less than or similar to 50 cm deep, is assumable within lunar soil of density 1.6 g/cm(3), a combination of thermal, epithermal, and fast neutron measurements enables concurrent estimation of water abundance and depth. To accurately understand the subsurface water abundance and depth across exploration areas along the rover's path, a comprehensive assessment of leakage neutrons in a wide energy range becomes indispensable.

N. Tsuji,a,b,∗ T. Enoto, H. Nagaoka, Y. Kato, K. Taniguchi, M. Hareyama, Y. Otake, Y. Wakabayashi, T. Takanashi, C. Iwamoto, T. Kobayashi, T. Ikenaga, Y. Nakano, Y. Tsukamoto, H. Kusano, f T. Tamagawa, T. Hoshino, M. Ueno, T. Morimoto, S. Yoshiura, M. Honma, H. Takahashi, j K. Nakazawa, K. Hotokezaka and S. Kisaka j Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan St. Marianna Univeristy School of Medicine, 2-16-1 Sugao, Kawasaki city, Kanagawa 216-8511, Japan Soil and Rock Engineering Co., Ltd., 2-21-1 Shonaisakaemachi, Toyonaka-shi, Osaka 561-0834, Japan f QST, 4-9-1 Anagawa, Inage-ku, Chiba-shi 263-8555, Japan JAXA, 7-44-1 Jindaiji Higashi-machi, Chofu-shi, Tokyo 182-8522, Japan Kindai University, 3-4-1 Kowakae, Higashiosaka city, Osaka 577-8502, Japan NAOJ, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Hiroshima University, 1-3-2 Kagamiyama, Higashi-Hiroshima City, Hiroshima 739-8511, Japan Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

A global classification map of lunar absorption spectra is developed under unified classification criteria by applying the K-means and ISODATA unsupervised classification methods. The spectra were obtained by the Spectral Profiler (SP) onboard the Kaguya (SELENE) lunar orbiter spacecraft. The spectra are mostly categorized into seven spectral groups by the K-means method: K1, K2, K3, K4, K5, K6, and K7. Then, each K-means group is divided into 66 total classes by the ISODATA method. The K1 and K3 groups are classified into 21 and 14 classes, respectively, for which the average spectra are high-calcium pyroxene (HCP)-abundant compared to the other groups. Both groups are mainly located on maria and pyroclastic deposits. However, while the K1 group can be found primarily near the center of large maria, the K3 group can be found mainly at small maria and the margins of large maria. The K2 group contains eight classes and shows average spectra, such as low-calcium pyroxene (LCP), in abundance, which are found mainly on the South Pole-Aitken (SPA) basin and on the coast of Mare Frigoris. The K5 (eight classes), K6 (two classes) and K7 (three classes) groups indicate average spectra with shallower absorption (between 0.9 mu m and 1.2 mu m wavelength) than those of the K1, K2, and K3 groups. These groups are located in highland regions, and the K5 group is located in high-albedo regions, such as fresh craters. The K6 group is found on nearside highland areas and the K7 group is found on farside highland areas. The K4 group with nine classes shows average spectra, such as mixtures of K1/K2/K3 and K5/K6/K7, and these classes are located around boundaries between mare/SPA and highland. In addition, one class is independently defined without using K-means and ISODATA because its spectra are unsuitable for automatic unsupervised classification. However, this class is still geologically meaningful. The average spectra of the ISODATA classes show not only the characteristics of the major host material belonging to a spectral group, but they also show the small influence of materials from other groups in nearby regions on that host material. This influence is considered to be caused by horizontal material mixing of materials in that location with the ejecta from nearby regions. However, occasionally the ISODATA classes of the K4, K5, and K6 groups influenced by the Kl/K3 groups are clustered geographically in regions far from the K1/K3 regions. Some locations of the clusters correspond to locations of the well-known cryptomaria and small pyroclastic deposits. On the other hand, some locations of them also contain candidates of hidden subterranean basaltic materials, such as undiscovered cryptomare, dike, and sill estimated based on recent lunar gravitational anomalies. This agreement suggests to be appeared hidden basaltic materials by the material mixing occurring vertically. The total area of the clusters except for known cryptomaria is approximately two times larger than that of the known cryptomaria, and this area reaches approximately 20% of the total area of exposed maria. The total volume of hidden basaltic materials, except for the known cryptomaria, is estimated to be 10(4) to 10(6) km(3), depending on assumptions of the relative abundance between cryptomare and dike/sill. This volume is comparable to that of the known cryptomaria and approximately 10% of that of the exposed mare.

The water-ice at the lunar polar regions is important from the viewpoint of scientific interest and future lunar utilization. According to some theoretical suggestions, water and other volatiles could be delivered to the Moon by comets and/or the solar wind, and they might be accumulated and trapped at cold spots as the permanently shadowed areas. Although several remote observations have indicated the presence of water-ice in lunar polar regions, its abundance and spatial distribution are still controversial issues. Recently, in Japan and other countries, lunar landing explorations at the polar region are being studied in order to obtain the abundance and distribution of water in the subsurface and to reveal the accumulation mechanism of water. The neutron spectroscopy is one of the best methods for in-situ water detection on the airless planetary surface. The galactic cosmic rays generate fast neutrons via nuclear spallation interaction in the subsurface materials at a depth of several tens centimeters. Then the fast neutrons are moderated to thermal and epithermal neutrons by interactions with subsurface materials, and this process is terminated at the thermal neutron capture or leakage of neutrons from surface. Since the hydrogen atom has a large elastic scattering cross section for a neutron and a nearly identical mass as a neutron, the neutrons are efficiently moderated by the elastic scattering with hydrogen atoms. Therefore, the leakage neutron flux strongly depends on the hydrogen abundance as well as the chemical composition of surface materials. investigated generated by galactic cosmic rays were calculated for different hydrogen abundance in the lunar polar material. The dependence of neutron fluxes on the spatial distribution of hydrogen were also studied on the several patterns of distribution. In addition, the neutron detection efficiency was estimated by assuming multiple neutron detectors in order to select and optimize the neutron spectrometer. An Li-glass scintillator, a B-loaded plastic scintillator, and a 3 He proportional counter were considered as neutron detectors. The preliminary calculation results will be presented, and the detection capability of water on the lunar landing exploration will be discussed.

Clarifying of lunar geological map is essential in understanding the initial formation of lunar crust and the mixing process of lunar surface rocks due to igneous activities and meteorite impacts. However, the global geological map has in the the which does not include various new knowledge found in recent exploration. we a project to a new global geological map of the Moon based on new data as topography, mineral and elemental composition acquired by lunar explorer of reflectance spectra obtained by Imager (MI) Kaguya, information of rock and mineral the data by MI and data processing for is to complete by working of only human’s eyes and hands. the classification be subjective the of mixed-random ICA to the reflectance spectra from lunar surface, though ICA has been adopted to lunar gamma-ray spectra obtained gamma-ray spectrometer onboard Kaguya [10]. It was found that the global maps of extracted ICs clearly showed some mineral and/or rocks distributions as true signals, some characteristic patterns as noises due to mechanical and observational conditions and many random noises. After ICA, the signal ICs are put in UC. This work employed ISODATA method as UC. ISODATA calculates class means evenly distributed in the data space then iteratively clusters the remaining pixels using minimum distance techniques. Users do not need to know the number of clusters and can define threshold values for parameters as minimum distance or minimum number of pixels for a class and so on. As a result, whole moon were divided into 50 -100 classes, though it was depended on the threshold values. This report will shows the detail procedure for classification of lunar reflectance spectra and discusses validity and applicability of this procedure based on the results.

Kaguya gamma-ray spectrometer measured thorium (Th) distribution on the lunar farside with the highest sensitivity among past gamma-ray remote sensing missions. The newly obtained Th map has revealed that two regions near the equator on the farside have the lowest Th abundances. We found that the variation of the Th abundance perfectly correlates with the crustal thickness in the farside and the southern nearside, and it could be a result of the crystallization of the lunar magma ocean.

Using Geographic Information Systems (GIS), we performed comparative analysis among stratigraphic information and the Kaguya (SELENE) GRS data of the ∼2500-km-diameter South Pole-Aitken (SPA) basin and its surroundings. Results indicate that the surface rock materials (including ancient crater materials, mare basalts, and possible SPA impact melt) are average to slightly elevated in K and Th with respect to the rest of the Moon. Also, this study demonstrates that K and Th have not significantly changed since the formation of SPA. The elemental signatures of the impact basin of Fe, Ti, Si, O through time include evidence for resurfacing by ejecta materials and late-stage volcanism. The oldest surfaces of SPA are found to be oxygen-depleted during the heavy bombardment period relative to later stages of geologic development, followed by both an increase in silicon and oxygen, possibly due to ejecta sourced from outside of SPA, and subsequent modification due to mare basaltic volcanism, which increased iron and titanium within SPA. The influence of the distinct geologic history of SPA and surroundings on the mineralogic and elemental abundances is evident as shown in our investigation.

The high precision gamma-ray spectrometer (GRS) is carried on the first Japan's large-scaled lunar explorer, SELENE (KAGUYA) circling a polar orbit. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals and a plastic scintillator as anticoincidence detectors. Since the successful launch on Sep. 14, 2007, radiation damage in the Ge detector has been induced from the incidence of energetic particles from space, which degraded its energy resolution. Then the Ge detector was annealed for 2 days at 85±5 K and the resolution is recovered to the level at the initial phase of the early observation. The special operations were conducted in December, 2008 in order to measure backgrounds gamma rays from the materials of the spacecraft body and the GRS instrument itself. The GRS data from the 100 km altitude reveal the global distribution of trace elements of Th and K on the Moon which delineates the distributions of KREEP component of lunar materials. Th and K-rich materials are concentrated around the Imbrium basin in Procellarum KREEP Terrane (PKT) and intermediately concentrated in South Pole–Aitken basin area on the farside. Results from special operations and observation are described and discussed.