The Japanese lunar explorer KAGUYA (SELENE) has been operating since nominal operations started in December 2007 to elucidate the origin and evolution of the Moon. Four KAGUYA research reports using observation data from the Terrain Camera onboard the KAGUYA and a perspective titled "Seeing the Missing Half" were published as part of a KAGUYA special edition in Science Magazine dated February 13, 2009. This special edition, which is featured on the cover page, is epoch-making and succeeds the special issues of planetoid explorer "HAYABUSA" in June 2006 and the solar observation satellite "HINODE" in December 2007.
The titles of the research reports in Science magazine that aim to provide new knowledge to stimulate the study of the origin and evolution of the Moon are as follows:
1) Lunar Radar Sounder Observations of Subsurface Layers under the Nearside Maria* of the Moon
2) Farside Gravity Field of the Moon from the Four-way Doppler Measurements of the SELENE (Kaguya)
3) The Lunar Global Shape and Polar Topography Derived from Kaguya-LALT Laser Altimetry
4) The Long-lived Volcanism on the Lunar Farside Revealed by the SELENE Terrain Camera
* The relay satellite "OKINA (RSTAR)" made an impact on the lunar surface on February 12, 2009 (JST), and the four-way Doppler measurement mission was successfully completed.
* Mare (Plural maria): Any of the large and low-lying dark areas on the Moon. The lunar maria is believed to consist of volcanic basalts.
Appendix: Research Reports Titles with Outlines
1) Lunar Radar Sounder Observations of Subsurface Layers under the Nearside Maria of the Moon
Takayuki Ono*1, Atsushi Kumamoto*1, Hiromu Nakagawa*1, Yasushi Yamaguchi*2, Shoko Oshigami*2, Atsushi Yamaji*3, Takao Kobayashi*4, Yoshiya Kasahara*5, Hiroshi Oya*6
*1 Tohoku University, *2 Nagoya University, *3 Kyoto University, *4 Korea Institute of Geoscience & Mineral Resources, * Kanazawa Univeristy, *6 Fukui University of Technology
2) Farside Gravity Field of the Moon from Four-way Doppler Measurements of SELENE (Kaguya)
- Radar sounding from the Kaguya spacecraft reveals subsurface layers at an apparent depth of several hundred meters in nearside maria.
- Comparison with the surface geology in the Serenitatis basin implies that the prominent echoes are probably from buried regolith layers accumulated during the depositional hiatus of mare basalts. The basalts that accumulated during this quiet period have a total thickness of only a few hundred meters. These observations suggest that mascon loading did not produce the tectonics in Serenitatis after 3.55 Ga. Global cooling probably dominated the tectonics after 2.84 Ga.
Noriyuki Namiki*1, Takahiro Iwata*2, Koji Matsumoto*3, Hideo Hanada*3, Hirotomo Noda*3, Sander Goossens*3, Mina Ogawa*2, Nobuyuki Kawano*3, Kazuyoshi Asari*3, Sei-itsu Tsuruta*3, Yoshiaki Ishihara*3, Qinghui Liu*3, Fuyuhiko Kikuchi*3, Toshiaki Ishikawa*3, Sho Sasaki*3, Chiaki Aoshima*4, Kosuke Kurosawa*5, Seiji Sugita*5, and Tadashi Takano*6
*1 Kyushu University, *2 JAXA, *3 NAOJ, *4 Fujitsu, *5 Tokyo University, *6 Nihon University
3) Lunar Global Shape and Polar Topography Derived from Kaguya-LALT Laser Altimetry
- The farside gravity field model of the Moon has been improved from the tracking data of the SELENE via a relay subsatellite "Okina (Rstar)." The new gravity field model reveals that the farside impact basins have concentric rings of positive-negative-positive anomalies unlike plateau-shaped positive anomalies of the nearside basins, suggesting rigid lithosphere on the farside and compensation at the crust-mantle boundary on the nearside. Farside basins are classified into two types depending on the magnitude of the central gravity high, indicating mantle uplift at a time of impact and association of mare volcanism with post-impact deformation. The basin structure possibly reflects the thermal state of the lithosphere, and gives an important clue to understand the thermal evolution of the Moon.
H. Araki*1, S. Tazawa*1, H. Noda*1, Y. Ishihara*1, S. Goossens*1, S. Sasaki*1, N. Kawano*1, I. Kamiya*2, H. Otake*3, J. Oberst*4, C. Shum*5
*1 National Astronomical Observatory *2 Geographical Survey Institute, *3 JAXA, *4 German Aerospace Center, *5 Ohio State University
4) Long-lived Volcanism on the Lunar Farside Revealed by SELENE Terrain Camera
- A global lunar topographic map with a spatial resolution of finer than 0.5° has been derived using data from the laser altimeter (LALT) onboard the Japanese lunar explorer KAGUYA (SELENE). In a comparison with the previous Unified Lunar Control Network (ULCN 2005) model, the new map reveals unbiased lunar topography for scales finer than a few hundred kilometers. The newly derived lunar topographic spectrum indicates the lunar crust is rigid enough to support the surface topography that is rougher than that of the Earth, which may indicate the drier lithosphere of the Moon than the Earth.
- The highest point on the Moon is on the southern rim of the Dirichlet-Jackson basin and the lowest one is in the Antoniadi crater in the SPA. The topographic range is about 19.81 km, which is greater than the ULCN 2005 result that is 17.53 km for the next highest and lowest points whose positions are generally identical to our highest and lowest points with differences less than a few degrees.
Junichi Haruyama 1*, Makiko Ohtake*1, Tsuneo Matsunaga*2, Tomokatsu Morota*1, Chikatoshi Honda *1, Yasuhiro Yokota*1, Masanao Abe*1, Yoshiko Ogawa*2, Hideaki Miyamoto*3, Akira Iwasaki*3, Carle M. Pieters*4, Noriaki Asada*5, Hirohide Demura*5, Naru Hirata*5, Junya Terazono*5, Sho Sasaki*6, Kazuto Saiki*7, Atsushi Yamaji*8, Masaya Torii*9, Jean-Luc Josset*10
*1 JAXA, *2 NIES, *3 University of Tokyo, *4 Brown University, *5 University of Aizu, *6 NAOJ, *7 Osaka University, *8 Kyoto University, *10 Fujitsu, *11 Space Exploration Institute
- The formation ages of geological units in mare can be determined by crater counting based on the idea as "a newly created surface will accumulate craters with time." The Terrain Camera aboard the SELENE (KAGUYA) provides high resolution (10 m / pixel) images to sufficiently detect small craters. As a result of crater counting by TC observation data, several units at various locations including a part of the Mare* Moscoviense on the lunar farside show their younger ages, clustering at -2.5 Ga, which were much younger than previously known on some farside mare units (-3.0 Ga). This result means "volcanic activity on the lunar farside lasted longer than previously considered and may have occurred episodically." "The long-lived farside volcanism" will be an important key factor for consideration on the lunar thermal evolution.