Refereed Journal Papers

[chonda-01:2010, kitazato-01:2010, yoshiko-01:2010]

M. Ohtake, T. Matsunaga, Y. Yokota, S. Yamamoto, Y. Ogawa, T. Morota, C. Honda, J. Haruyama, K. Kitazato, H. Takeda, A. Iwasaki, R. Nakamura, T. Hiroi, S. Kodama, and H. Otake. Deriving the Absolute Reflectance of Lunar Surface Using SELENE (Kaguya) Multiband Imager Data. Space Science Review, 154:57-77, doi: 10.1007/s11214-010-9689-0., 2010.

The absolute reflectance of the Moon has long been debated because it has been suggested (Hillier et al. in Icarus 151:205-225, 1999 that there is a large discrepancy between the absolute reflectance of the Moon derived from Earth-based telescopic data and that derived from remote-sensing data which are calibrated using laboratory-measured reflectance spectra of Apollo 16 bulk soil 62231. Here we derive the absolute reflectance of the lunar surface using spectral data newly acquired by SELENE (Kaguya) Multiband Imager and Spectral Profiler. The results indicate that the reflectance of the Apollo 16 standard site, which has been widely used as an optical standard in previous Earth-based telescopic and remote-sensing observations derived by Multiband Imager, is 47% at 415 nm and 67% to 76% at 750 to 1550 nm of the value for the Apollo 16 mature soil measured in an Earth-based laboratory. The data also suggest that roughly 60% of the difference is caused by the difference in soil composition and/or maturity between the 62231 sampling site and the Apollo 16 standard site and that the remaining 40% difference can be explained by the difference between the compaction states of the laboratory and the actual lunar surface. Consideration of the compaction states of the surface soil demonstrates its importance for understanding the spectral characteristics of the lunar surface. We also explain and evaluate data analysis procedures to derive reflectance from Multiband Imager data

[chonda-02:2010, demura-03:2010, naru-02:2010, yoshiko-02:2010]

T. Morota, J. Haruyama, M. Ohtake, T. Matsunaga, C. Honda, Y. Yokota, J. Kimura, Y. Ogawa, N. Hirata, H. Demura, A. Iwasaki, T. Sugihara, K. Saiki, R. Nakamura, S. Kobayashi, Y. Ishihara, H. Takeda, and H. Hiesinger. Timing and characteristics of the latest mare eruption on the Moon. Earth and Planetary Science Letters, 302:255-266, doi: 10.1016/j.epsl.2010.12.028, February 2011.

Unraveling the timing and duration of mare volcanism on the Moon is essential for understanding its thermal evolution. The end of mare volcanism is poorly constrained, because mare basalts are incompletely sampled. In this study, employing SELENE (Kaguya) high-resolution images, we performed new crater size-frequency measurements for 49 young mare units (<measurements for 49 young mare units (<˜ 3.0 Ga) in the Procellarum KREEP 3.0 Ga) in the Procellarum KREEP Terrane (PKT), in which the latest magma eruption of the Moon occurred. Mare volcanism in this region continued until volcanism in this region continued until ? 1.5 Ga, suggesting that volcanic activity 1.5 Ga, suggesting that volcanic activity in this region ceased in this region ceased ? 1.0 Ga after the magma eruption had globally ceased 2.5-3.0 1.0 Ga after the magma eruption had globally ceased 2.5-3.0 Ga. Volcanic activity may have peaked 1.8-2.2 Ga ago. The youngest basalts occur around the Aristarchus plateau and the Kepler crater, which are located in the central region of the PKT. It is likely that heating in the crust due to the concentration of heat-producing elements in the PKT delayed cooling of a partial-melting zone in the underlying mantle. In contrast with previous basalt dating in this region, our results indicate a higher correlation between ages and spectral types of mare basalts; the young mare units in the PKT tend to have spectral types corresponding to high titanium contents, while low titanium basalts occur mainly in the early stage. The titanium variation in mare basalts may reflect vertical heterogeneity in TiO2 content in the upper mantle beneath the PKT.

[demura-04:2010, naru-05:2010]

S. Kodama, M. Ohtake, Y. Yokota, A. Iwasaki, J. Haruyama, T. Matsunaga, R. Nakamura, H. Demura, N. Hirata, T. Sugihara, and Y. Yamamoto. Characterization of Multiband Imager Aboard SELENE. Pre-flight and In-flight Radiometric Calibration. Space Science Reviews, 154:79-102, 2010.

The Multiband Imager (MI) is a high-resolution, multi-spectral imaging instrument for lunar exploration. It consists of two cameras, VIS and NIR, and is carried on the SELenological and ENgineering Explorer (SELENE), launched on Sep. 14, 2007. During the observation from January 2008 to June 2009, MI acquired about 450,000 scenes of multispectral image. The radiometric properties of the cameras were characterized using the pre-flight data derived in laboratory experiments with a calibrated integrating sphere. Twelve light source sets were used to examine the S/N ratio, linearity, and saturation level of the cameras. The dark field signal is quite stable in both cameras, having a noise level of less than 1 DN (VIS) and 2 DN (NIR). The fluctuation in the light field is also low (<2 DN), indicating that the spatial nonuniformity in the camera responses can be removed using a flat field. In order to remove the smear signals due to the frame transfer in the VIS data, we developed an iterate algorithm using all bands in the VIS camera. The S/N ratio, which is critical to the precision of the product, is estimated to exceed 160 for the VIS bands and 400 for the NIR bands under low illumination conditions (5% of lunar surface reflectance). Based on the S/N ratio, the radiometric error due to the noise is calculated to be less than 0.7% for VIS and 0.2% for NIR. The relationship between input and output of the VIS camera is linear with a residual of less than 0.6 DN, corresponding to a radiometric error of 0.3The NIR exhibits a non-linear response to the input radiance. A cubic function best fits the pre-flight data with an average residual of 8 DN (corresponds to an error of 0.8%). Validation using in-flight data indicated that the instability of the dark output has not changed, but the level of dark output has slightly changed in the NIR bands (less than 6 DN). The pixel-to-pixel sensitivity variation in the orbit has been changed from that in the pre-flight experiment. The difference between the in-flight data and the pre-flight data ranges within +/- 2%. There is also a small (less than +/- 1%) but nonnegligible difference between in-flight data of different cycles in both the VIS and NIR bands, suggesting that the coefficient for spatial ununiformity correction needs to be calculated for each cycle.

[demura-02:2010, kitazato-02:2010, naru-01:2010]

M. Ishiguro, R. Nakamura, D. J. Tholen, N. Hirata, H. Demura, E. Nemoto, A. M. Nakamura, Y. Higuchi, A. Sogame, A. Yamamoto, K. Kitazato, Y. Yokota, T. Kubota, T. Hashimoto, and J. Saito. The Hayabusa Spacecraft Asteroid Multi-band Imaging Camera (AMICA). Icarus, 207:714-731, 2010.

The Hayabusa Spacecraft Asteroid Multi-band Imaging Camera (AMICA) has acquired more than 1400 multispectral and high-resolution images of its target asteroid, 25143 Itokawa, since late August 2005. In this paper, we summarize the design and performance of AMICA. In addition, we describe the calibration methods, assumptions, and models, based on measurements. Major calibration steps include corrections for linearity and modeling and subtraction of bias, dark current, readout smear, and pixel-to-pixel responsivity variations. AMICA v-band data were calibrated to radiance using in-flight stellar observations. The other band data were calibrated to reflectance by comparing them to ground-based observations to avoid the uncertainty of the solar irradiation in those bands. We found that the AMICA signal was linear with respect to the input signal to an accuracy of +/-1% when the signal level was <3800 DN. We verified that the absolute radiance calibration of the AMICA v-band (0.55 um) was accurate to 4% or less, the accuracy of the disk-integrated spectra with respect to the AMICA v-band was about variation was 3% or less. The uncertainty in background zero level was 5 DN. From wide-band observations of star clusters, we found that the AMICA optics have an effective focal length of 120.80 +/- 0.03 mm, yielding a field-of-view (FOV) of 5.83x5.69 deg. The resulting geometric distortion model was accurate to within a third of a pixel. We demonstrated an image-restoration technique using the point-spread functions of stars, and confirmed that the technique functions well in all loss-less images. An artifact not corrected by this calibration is scattered light associated with bright disks in the FOV.

[demura-01:2010]

H. Demura. Shape Modeling of Asteroids Based on Camera Images. Journal of the Japanese Society for Artificial Intelligence, 26(2):184-187, 2010. in Japanese

[naru-09:2010]

N. Asada, N. Miura, H. Demura, and N. Hirata. Automatic tracking of impact fragments. World Review of Science, Technology and Sust. Development, 7:181-194, 2010.

In general, it is difficult to understand how the object was before collision and what had happened during collision after a collision has destroyed them. The motion analysis of the collision destruction phenomenon is extremely important as a help of the total analysis of the destruction process and the automation of the motion analysis of impact fragments has been requested in the field of hypervelocity impact experiments. Some fragments were automatically tracked on images cut from an impact experiment moving picture. A combination method of the two dimensional continuous dynamic programming (2DCDP) method proposed by Oka (1998) and the Helmert transform is proposed and applied in tracking fragments. After some improvements, tracking of fragments was performed sufficiently and the effectiveness of this method was confirmed. As a result, physical quantities of impact fragments such as translation velocities, rotation velocities and so on were derived from the analysis. calibrated to reflectance by comparing them to ground-based observations to

[naru-04:2010, yoshiko-03:2010]

S. Yamamoto, R. Nakamura, T. Matsunaga, Y. Ogawa, Y. Ishihara, T. Morota, N. Hirata, M. Ohtake, T. Hiroi, Y. Yokota, and J. Haruyama. Possible mantle origin of olivine around lunar impact basins detected by SELENE. Nature Geoscience, 3:533-536, doi:10.1038/ngeo897, 2010.

The composition, structure and evolution of the Moon's mantle is poorly constrained. The mineral olivine, one of the main constituents of Earth's mantle, has been identified by Earth-based telescopic observations at two craters on the near side of the Moon, Aristarchus and Copernicus. Global reflectance spectra in five discrete spectral bands produced by the spacecraft Clementine suggested several possible olivine-bearing sites, but one of the candidate occurrences of olivine was later reclassified, on the basis of continuous reflectance spectra over the entire 1um band, as a mixture of plagioclase and pyroxene. Here we present a global survey of the lunar surface using the Spectral Profiler onboard the lunar explorer SELENE/Kaguya. We found many exposures of olivine on the Moon, located in concentric regions around the South Pole-Aitken, Imbrium and Moscoviense impact basins where the crust is relatively thin. We propose that these exposures of olivine can be attributed either to an excavation of the lunar mantle at the time of the impacts that formed the basins, or to magnesium-rich pluton in the Moon's lower crust. On the basis of radiative transfer modelling, we suggest that at least some of the olivine detected near impact basins originates from upper mantle of the Moon.

[naru-03:2010]

N. Asada, N. Hirata, H. Demura, N. Harada, Y. Shibata, S. Kikuchi, T. Hodokuma, J. Haruyama, M. Ohtake, Y. Yokota, T. Morota, C. Honda, T. Matsunaga, Y. Ogawa, M. Torii, T. Nimura, H. Araki, and S. Tazawa. Computational Geology for Lunar Data Analysis from LISM on KAGUYA. Advances in Geosciences, Volume 19: Planetary Science (SE), 19:77, 2010. Not Available

[saji-01:2010]

L. Stefanova, V. Misra, J.J. OBrien, E. P. Chassignet, and N H Saji. Hindcast skill and predictability for precipitation and two-meter air temperature anomalies in global circulation models over the Southeast United States. Climate Dynamics, (DOI 10.1007/s00382-010-0988-7):15, 2011.

This paper presents an assessment of the seasonal prediction skill of current global circulation models, with a focus on the two-meter air temperature and precipitation over the Southeast United States. The model seasonal hindcasts are analyzed using measures of potential predictability, anomaly correlation, Brier skill score, and Gerrity skill score. The systematic differences in prediction skill of coupled oceanatmosphere models versus models using prescribed (either observed or predicted) sea surface temperatures (SSTs) are documented. It is found that the predictability and the hindcast skill of the models vary seasonally and spatially. The largest potential predictability (signal-to-noise ratio) of precipitation anywhere in the United States is found in the Southeast in the spring and winter seasons. The maxima in the potential predictability of two-meter air temperature, however, reside outside the Southeast in all seasons. The largest deterministic hindcast skill over the Southeast is found in wintertime precipitation. At the same time, the boreal winter two-meter air temperature hindcasts have the smallest skill. The large wintertime precipitation skill, the lack of corresponding two-meter air temperature hindcast skill, and a lack of precipitation skill in any other season are features common to all three types of models (atmospheric models forced with observed SSTs, atmospheric models forced with predicted SSTs, and coupled oceanatmosphere models). Atmospheric models with observed SST forcing demonstrate a moderate skill in hindcasting spring-and summertime two-meter air temperature anomalies, whereas coupled models and atmospheric models forced with predicted SSTs lack similar skill. Probabilistic and categorical hindcasts mirror the deterministic findings, i.e., there is very high skill for winter precipitation and none for summer precipitation. When skillful, the models are conservative, such that low-probability hindcasts tend to be overestimated, whereas high-probability hindcasts tend to be underestimated.

[sampe-01:2010]

T. Sampe, H. Nakamura, A. Goto, and W. Ohfuchi. Significance of a midlatitude SST frontal zone in the formation of a storm track and an eddy-driven westerly jet. Journal of Climate, 23:1793-1814, 2010.

In a set of idealized 'aquaplanet' experiments with an atmospheric general circulation model to which zonally uniform sea surface temperature (SST) is prescribed globally as the lower boundary condition, an assessment is made of the potential influence of the frontal SST gradient upon the formation of a storm track and an eddy-driven midlatitude polar front jet (PFJ), and on its robustness against changes in the intensity of a subtropical jet (STJ). In experiments with the frontal midlatitude SST gradient as that observed in the southwestern Indian Ocean, transient eddy activity in each of the winter and summer hemispheres is organized into a deep storm track along the SST front with an enhanced low-level baroclinic growth of eddies. In the winter hemisphere, another storm track forms just below the intense STJ core, but it is confined to the upper troposphere with no significant baroclinic eddy growth underneath. The near-surface westerlies are strongest near the midlatitude SST front as observed, consistent with westerly momentum transport associated with baroclinic eddy growth. The sharp poleward decline in the surface sensible heat flux across the SST frontal zone sustains strong near-surface baroclinicity against the relaxing effect by vigorous poleward eddy heat transport. Elimination of the midlatitude frontal SST gradient yields marked decreases in the activity of eddies and their transport of angular momentum into midlatitudes, in association with equatorward shifts of the PFJ-associated low-level westerlies and a subtropical high pressure belt, especially in the summer hemisphere. These impacts of the midlatitude frontal SST gradient are found to be robust against modest changes in the STJ intensity as observed in its interannual variability, suggesting the potential importance of midlatitude atmosphereëcean interaction in shaping the tropospheric general circulation.

Refereed Proceedings Papers

[kitazato-03:2010]

T. Harada, K. Kitazato, N. Hirata, and H. Demura. A rover simulation tool for small body exploration. In 42nd Lunar and Planetary Science Conference, number #1370, March 2011.

We have developed a simulation tool of the hopping rover for small body exploration. This simulator implements physics-based computing of the rover motion and its visualization.

[kitazato-04:2010]

K. Kitazato, M. Abe, Y. Takagi, T. Matsunaga, M. Ohtake, N. Takato, and T. Hiroi. NIRS-3: a near-infrared spectrometer for the Hayabusa-2 mission. In American Astronomical Society, DPS meeting #42, number #49.02, October 2010.

The NIRS-3, a near-infrared spectrometer that will benefit the heritage of NIRS on Hayabusa, has been proposed to characterize the mineralogical composition of asteroid surfaces in Hayabusa-2. The Hayabusa-2 mission aims to return samples of a C-class asteroid, on which hydrated minerals are often present and provide spectral features to determine compositions. Particularly diagnostic absorption features due to hydrated minerals appear in the 3-micron region. Thus the NIRS-3 focuses on 3-micron observations of the target asteroid, which will provide information for the selection and characterization of sampling sites and information concerning the composition and thermal evolution of the asteroid. We present the instrument design and expected performance of NIRS-3.

[kitazato-05:2010, yoshiko-04:2010]

T. Sugawara, K. Kitazato, Y. Ogawa, N. Hirata, T. Matsunaga, R. Nakamura, S. Yamamoto, and Y. Yokota. Evaluation of thermal components in the Kaguya SP/NIR2 spectral data. In 42nd Lunar and Planetary Science Conference, number #2256, March 2011.

This study focuses on determining thermal components of the NIR2 spectral data for its calibration. We evaluated thermal flux from the instrument interior using the observing data of the onboard calibration module.

[yoshiko-05:2010]

M. Ohtake, T. Mastunaga, H. Takeda, Y. Yokota, S. Yamamoto, T. Morota, Y. Ogawa, T. Hiroi, R. Nakamura, and J. Haruyama. Vertical Compositional Trend Within the Lunar Highland Crust. In 42nd Lunar Planet. Sci., page Abstract#1169, March 2011.

We investigated spatial and vertical compositional (modal abundance) trends of these high plagioclase abundance anorthosite rocks over the entire lunar surface within the upper crust.

[yoshiko-06:2010]

S. Yamamoto, R. Nakamura, T. Matsunaga, Y. Ogawa, Y. Ishihara, T. Morota, N. Hirata, M. Ohtake, T. Hiroi, Y. Yokota, and J. Haruyama. Distribution of Olivine-Rich Sites in the South-Pole Aitken Basin Revealed by SELENE Spectral Profiler. In 42nd Lunar Planet. Sci., page Abstract#1184, March 2011.

We report the distribution of olivine exposures in the South-Pole Aitken basin discovered by the Spectral Profiler onboard the Japanese lunar Explorer SELENE (Kaguya).

[yoshiko-07:2010]

Y. Ogawa, T. Matsunaga, R. Nakamura, K. Saiki, T. Hiroi, H. Takeda, M. Ohtake, T. Arai, Y. Yokota, S. Yamamoto, T. Sugihara, S. Sasaki, J. Haruyama, N. Hirata, T. Morota, C. Honda, H. Demura, K. Kitazato, J. Terazono, and N. Asada. Widespread occurrence of high-calcium pyroxene in bright-ray craters on the lunar highland discovered by the Spectral Profiler onboard SELENE (Kaguya). In 2010 The Meeting of the Americas (invited talk), pages Abstract#P41A01, August 2010.

The petrologic nature and vertical structure of the lunar highland crust afford important clues for understanding the evolution of the Moon, but they are not well understood. We investigated the continuous spectral features of craters ranging from 8 to 24 km in cavity diameter with distinctive bright rays on the lunar highland using the Spectral Profiler (SP) onboard SELENE (Kaguya). Using the newly obtained SP data, which give highly critical information for identifying the mineralogical composition of lunar surface areas with unprecedented accuracy, we found that the observed spectra showed strong symmetric absorption around 1 m and recognizable absorption around 1.3 m. The spectra around a few craters showed a drastic change in the relative strengths of these two absorption bands (s1.3/1.0) depending on the location in and around the crater, which we interpreted as due to the variation in the mixing ratio of mafic minerals and plagioclase, whereas most of the craters showed no variation in the spectral shape around the craters, with an essentially constant s1.3/1.0. We analyzed the absorption features of the ubiquitously observed spectra with an essentially constant s1.3/1.0 using the Modified Gaussian Model and identified the dominant mafic minerals in the bright-ray craters. We found that the strongest, symmetric absorption band centers were at 0.97-1.01 m with s1.3/1.0 0.2-0.6. Comparing these values with data for known samples, we concluded that high-calcium pyroxene (HCP) is the most plausible dominant mafic mineral identified from the observed spectra. We discuss the potential origins of the observed HCP and also refer to the possibility that the major mafic component of some portions of the crust is HCP.

[yoshiko-08:2010]

Shizuka Suzuki, Chikatoshi Honda, Naru Hirata, Tomokatsu Morota, Noriaki Asada, Hirohide Demura, Yoshiko Ogawa, Kohei Kitazato, Jun-Ya Terazono, Makiko Ohtake, Junichi Haruyama, and Tsuneo Matsunaga. Preliminary Result of Optical Maturity of Small Rayed Lunar Craters. In 38th COSPAR Scientific Assembly Symposium B, session 01, pages Abstract#B01-0070-10, July 2010.

The purpose of this research is to estimate the formation age of small rayed lunar craters which is composed of ejecta blanket derived from impact cratering by using OMAT (Optical MATuriry) parameter developed by Lucey et al. (2000) based on Clementine UV/VIS data. The OMAT parameter is the optical index of degree of space weathering which provides planetary surface materials with redding and darkened on spectral characteristics, and is defined as the Euclidean distance between the reflectance at 750 nm and the 950/750 nm ratio value. It has been suggested that OMAT value reduces as space weathering of lunar surface materials progresses with exposured time. Therefore, the OMAT parameter could be an index of relative surface age. However, it is necessary to examine detail correlation between OMAT parameter and surface age for constructing an OMAT model chronometer. Grier et al. (2001) have showed the correlation between average OMAT value as a function of distance from the crater center and formation age of each large crater more than about 20 km in diameter. In their result, we recognize that better correlation between the OMAT and the formation age of highland craters such as Giordano Bruno, Necho, and Tycho craters. On the other hand, in mare units, whether the craters have rays depends on not only OMAT but also the difference of reflectance between the rayed materials and substrate ground materials. So, it is difficult to distinguish a high OMAT rayed craters from other craters in the mare units. We focused on lunar craters in highland, and investigate the correlation between the formation ages of rayed craters (Giordano Bruno, Tycho, Byrgius A, Necho, and Jackson) estimated by crater counting or radiometric age of rock samples and OMAT values of these craters as a function of distance from the crater's center using Kaguya/MI (Multiband Imager) mosaic images which provide us with the reflectance of the lunar surface with topographic correction. Based on this correlation, we could be able to estimate model formation ages of small rayed craters less than 1 km in diameter. As a consequence, the crater production rate function might be refined by age estimation of several numbers of small rayed craters.

[yoshiko-09:2010]

G. Kramer, S. Besse, C. Neish, H. Tsunakawa, J. Haruyama, Y. Saito, T. Matsunaga, Y. Ogawa, M. Ohtake, Y. Futaana, M. Wieser, J. Bandfield, T. Glotch, and E. Harnett. New Data Integration Towards Solving the Mystery of the Lunar Swirls. In 42nd Lunar Planet. Sci., page Abstract#1965, March 2011.

We are beginning a re-evaluation of the lunar swirls through the synthesis of new instrument data and the active collaboration of experts in the scientific fields from which these instruments derive.

[yoshiko-10:2010]

Noriaki Asada, Naru Hirata, Hirohide Demura, Naoto Harada, Yuto Shibata, Shota Kikuchi, Tomoki Hodokuma, Junichi Haruyama, Makiko Ohtake, Yasuhiro Yokota, Tomokatsu Morota, Chikashi Honda, Tsuneo Matsunaga, Yoshiko Ogawa, Masaya Torii, Tokuhiro Nimura, Hiroshi Araki, and Seiichi Tazawa. Computational Geology for Lunar Data Analysis from LISM on KAGUYA. In Advances in Geosciences, page 77, May 2010. Computational Geology for Lunar Data Analysis from LISM on KAGUYA

[yoshiko-11:2010]

S. Suzuki, C. Honda, N. Hirata, N. Asada, H. Demura, K. Kitazato, Y. Ogawa, J. Terazono, T. Moroda, M. Ohtake, J. Haruyama, and T. Matsunaga. Retention time of rays around small lunar craters. In American Geophysical Union, Fall Meeting 2010,, pages Abstract#P53C1536, December 2010.

Fresh lunar impact craters have rays which are bright features radially expanding from host craters. It has been suggested that the rays are erased by space weathering that modify surface materials by exposure to solar wind and micrometeorite bombardments, and by impact gardening that mixes surface materials and subsurface materials by meteorite bombardments (Wilhelms, 1987). Werner and Medvedev (2010) surveyed lunar rayed craters with Clementine UVVIS images and showed that retention time of the rays of craters larger than 5 km in diameter is 750 Myr. The purpose of this research is to estimate the retention time of rays around smaller lunar craters with high-resolution multiband images from Kaguya/MI (Multiband Imager). In our research, we surveyed rayed craters using OMAT (Optical Maturity) parameter developed by Lucey et al. (2000). The OMAT parameter is the optical index representing the degree of space weathering, which is derived from multiband images. Crater rays are not only bright, but also have larger OMAT value than the background. We conducted a survey of rayed craters from 300 m to 2 km in diameter in lunar highland with MI images and MI-OMAT data. A crater size-frequency distribution (CSFD) plot is constructed for detected small rayed craters. Our preliminary result suggest that the CSFD of the rayed craters of less than 1 km in diameter falls beneath an isochrone 750 Ma, the ray retention time for large craters estimated by Werner and Medvedev (2010). This result supports an idea that the retention time of rayes depends on the crater diameter (Werner and Medvedev, 2010). Smaller craters would show shorter ray retention times.

[yoshiko-12:2010]

M. Ohtake, T. Matsunaga, H. Takeda, Y. Yokota, S. Yamamoto, T. Moroda, Y. Ogawa, T. Hiroi, R. Nakamura, and J. Haruyama. Composition of the lunar upper crust estimated from Kaguya spectral data. In American Geophysical Union, Fall Meeting 2010, pages Abstract #P51C 1441, December 2010.

The magma ocean hypothesis has been the most widely accepted mechanism explaining the generation of the lunar highland crust. This hypothesis is based on analyses of returned samples [1] and an assumption that Fe-bearing, plagioclase-rich rocks exist globally as the major component of the lunar crust. However, no crystalline plagioclase had been detected by remote sensing before SELENE [2], except for some ambiguous or indirect indications of the existence of plagioclase. Subsequently, a global distribution of rocks of extremely high plagioclase abundance (approaching 100 vol%; called purest anorthosite (PAN)) was reported using an unambiguous plagioclase absorption band around 1250 nm found by the SELENE Multiband Imager (MI) [3]. The estimated plagioclase abundance is significantly higher than previous estimates of 82 to 92 vol% [1], providing a valuable constraint on models for lunar magma ocean evolution. Further study using continuous reflectance spectra derived by the SELENE Spectral Profiler (SP) [4] revealed a global and common distribution of the PAN over the entire lunar surface, supporting the high abundance of PAN rocks within the upper crust. In this study, we investigated a vertical compositional (modal abundance and/or mineral composition) trend of the PAN rocks within the crust using their reflectance spectra derived from SP and MI. Knowing the compositional trend of the lunar upper crust may enable us to understand the mechanism of the lunar crustal growth. All of the SP data observed throughout SELENE mission periods were used in this study (about 7,000 orbits and roughly 10,000 spectra for each orbit). The absorption depth at each wavelength was calculated after a linear continuum was removed. Spectra with the deepest absorption depth, around 1250 nm, which is caused by a minor amount of Fe2+ (in the order of 0.1 wt% FeO) contained in the plagioclase, were selected to detect the PAN rocks. The original burial depth of each PAN rock outcrop was estimated from a crater scaling law using the crater diameter of each outcrop observed in MI data. Results indicate that the majority of the derived absorption depths (strengths) of the detected PAN rock spectra around 1250 nm appear to form a trend which increases as their estimated original burial depths increase within the crust (the trend is observed up to 30 km of the original burial depth). Although understanding the actual cause of this trend requires further studies, such a trend may indicate a decrease in the mafic mineral abundance within the already very mafic-poor rock and/or an increase in the Fe2+ content of plagioclase with depth. References: [1] Warren P. H. (1990) Am. Mineral., 75, 46-58. [2] Matsunaga T. et al. (2008) Geophys. Res. Let., 35, L23201, doi:10.1029/2008GL035868. [3] Ohtake M. et al. (2009) Nature, 461, doi:10.1038. [4] Ohtake et al. (2010) Lunar Planet. Sci. Conf. XXXXI, 1628.

[yoshiko-13:2010]

Junichi Haruyama, Makiko Ohtake, Tsuneo Matsunaga, Tomokatsu Morota, Haruo Kawasaki, Chikatoshi Honda, Yasuhiro Yokota, Masaya Torii, Masanao Abe, Hisashi Otake, Tokuhiro Nimura, Yoshiko Ogawa, Atsushi Yamaji, Hiroshi Takeda, Motomaro Shirao, Noriaki Asada, Hirohide Demura, Naru Hirata, Junya Terazono, Shinsuke Kodama, Ryosuke Nakamura, Shigeyuki Minami, Akira Iwasaki, Hideaki Miyamoto, Tomoko Arai, Takamitsu Sugihara, Yasushi Yamaguchi, Kazuto Saiki, Takahiro Hiroi, Sho Sasaki, Hiroaki Akiyama, Seiichi Hara, Kazuyuki Hioki, Moji Hashimoto, Yutaka Kurashina, Kenji Torii, Akira Yoshizawa, Shunsuke Nakanotani, Junichi Inoue, Naoyuki Masuda, Jean-Luc Josset, and Carle M. Pieters. Preliminary Results of the SELENE Terrain Camera. In Transactions of Space Technology Japan, pages Tk 61Tk 66, doi: 10.2322/tstj.7.Tk 61, 2010.

On September 14, 2007, Moon explorer SELENE (Kaguya) was launched to the Moon carrying a 10-m spatial resolution stereo-camera, the Terrain Camera (TC). Particular mission objectives of the TC include Polar regions and Mare regions such as Oceanus Procellarum, South-Pole to Aitken basin, and Mare Orientale, that have not been observed with TC's high-resolution stereoscopy. The first TC data of the Moon were obtained on Nov. 3, 2007. We confirmed 1) that the TC had not generated any defective pixels and would achieve high signal-to-noise ratio (S/N) performance and 2) that the TC could provide high-quality data in the Polar regions and a 180 km region extending from 60N to 66N along 240E. We could acquire scientific information from ortho images and digital terrain models (DTMs) produced from these TC first data. On Nov. 24, 2007, we acquired several sequential strip data, from which a seamless mosaicked TC ortho image and DTMs were successfully produced. These seamless mosaicked data will be very useful for investigating large mare regions. After completion of the nominal checkout phase on Dec. 21, 2007, the TC began the nominal mission operation phase with other mission instruments. Thus, we could confirm that TC will provide fundamental assets for lunar science from the initial checkout phase data.

[yoshiko-14:2010]

Chikatoshi Honda, Masashi Toguchi, Tomokatsu Morota, Naru Hirata, Hirohide Demura, Noriaki Asada, Kohei Kitazato, Yoshiko Ogawa, Jun-Ya Terazono, and Junichi Haruyama. Age of large volcanism to originate the Vallis Schroteri on the Moon. In 38th COSPAR Scientific Assembly Symposium B, session 01, pages Abstract#B01-0043-10, July 2010.

The Vallis Schruteri on the Aristarchus Plateau of the Moon is a meandering negative depres-o sion, as called a sinuous rille. The sinuous rille is located at 26.2 N deg. in latitude and 50.8 W deg. in longitude. This is the largest sinuous rille on the moon, which is 168 km in length, 6 km in width, and 500 m on average in depth (less than 1 km) [Honda et al., 2009]. The sinuous rille has been suggested that the negative depression was produced by an ancient huge lava flow which eroded into the substrate ground. The volume of lava flow to produce the negative depression seemed to be the largest among volcanisms on the Moon. However, an age of this volcanic event is not estimated yet. Therefore, it is important to estimate the formation age of the Vallis Schruteri for understanding of thermal evolution of the Moon. We utilize the crater chronology method using the crater size-frequency distribution for the age estimation of the sinuous rille, because the ability of suitable high resolution images of Kaguya/TC lead us to measure an accurate diameter of small craters in the sinuous rille. We should remove secondary craters from our measurements to acquire more accurate age estimation. There is the Aristarchus crater, 40 km in diameter, nearby the Vallis Schruteri, so we eliminated the area blanketed by ejecta from the crater by using the Clementine and Kaguya/MI data and carefully remove the secondary craters showing the herringbone, cluster, chains, and elongated characteristics. We examined areas of the floor of the Vallis Schruteri, and of southwestern outside of the Aristarchus Plateau which is suspected as the lava pond to produce the Vallis Schruteri by spectral data. If these areas are originated by same lava flow, no difference of the results of age estimation among the areas. As a result, we estimated the formation age of the floor part of the Vallis Schruteri, as 2.5 (+0.4, -0.4) Ga, and the age of the lava pond, as 3.1 (+0.3, -0.7) Ga. The results show us that the possibility of lava pond to originate the Vallis Schruteri suspicious. And, the formation age of the Vallis Schruteri lead us to know an occurrence of large volcanism in the Eratosthenian which is fade-out period of more active volcanisms (Imbrian) on the Moon.

Unrefereed Papers

[chonda-03:2010]

K. Saiki, T. Arai, H. Araki, Y. Ishihara, M. Ohtake, Y. Karouji, N. Kobayashi, T. Sugihara, J. Haruyama, and C. Honda. Progress Report on Landing Site Evaluation for the Next Japanese Lunar Exploration Project: SELENE-2. In American Geophysical Union, Fall Meeting 2010, pages #P51C 1462, December 2010.

SELENE-2 is the next Japanese lunar exploration project that is planned to be launched by the end of fiscal year 2015...

[chonda-04:2010]

S. Suzuki, C. Honda, N. Hirata, N. Asada, H. Demura, K. Kitazato, Y. Ogawa, J. Terazono, T. Moroda, M. Ohtake, J. Haruyama, and T. Matsunaga. Retention time of rays around small lunar craters. In American Geophysical Union, Fall Meeting 2010, pages #P53C1536, December 2010.

Fresh lunar impact craters have rays which are bright features radially expanding from host craters...

Grants

[demura-05:2010, yoshiko-15:2010]

H. Demura, Y. Ogawa, and Y. Takahashi. Competitive Research Fund for Development of Scientific Instruments FY2010, Environment Test for Liquid Crystal Tunable Filter, 2010.

[kitazato-06:2010]

K. Kitazato. JSPS Research Activity Start-up, 2010-2011.

Academic Activities

[naru-08:2010]

N. Hirata, 2010.

Member, and member of the committee for general affairs, The Japanese Society for Planetary Sciences

[naru-10:2010]

N. Hirata, 2010.

Member of Local Organizing Committee, Asteroid, Comet, Meteor meeting 2011

[naru-07:2010]

N. Hirata, 2010.

Member of Program Subcommittee, The 28th International Symposium on Space Technology and Science

[sampe-02:2010]

T. Sampe, 2010.

Reviewer for Journal of Meteorological Society of Japan

[sampe-03:2010]

T. Sampe, 2010.

Reviewer for Journal of Climate (published by American Meteorological Society)

[yoshiko-16:2010]

Y. Ogawa, April 2010.

committee member of JGU gender equality, Japan Geoscience Union JGU

[yoshiko-17:2010]

Y. Ogawa, April 2010.

normal member, The Japanese Society for Planetary Sciences

[yoshiko-18:2010]

Y. Ogawa, April 2010.

normal member, American Geophyisical Union