|
|
|
|
|
|
|
|
PIP-06 Origin and evolution of the Moon
|
|
|
|
Geologic interpretation of the lunar maria by Lunar Radar Sounder (LRS) onboard Kaguya (SELENE)
|
|
|
|
Yasushi Yamaguchi, Nagoya University (Japan)
Atsushi Yamaji, Kyoto University (Japan)
Takayuki Ono, Tohoku University (Japan)
Atsushi Kumamoto, Tohoku University (Japan)
Shoko Oshigami, Nagoya University (Japan)
Hiromu Nakagawa, Tohoku University (Japan)
Takao Kobayashi, Korea Institute of Geoscience and Mineral Resources (Republic of Korea)
Yoshiya Kasahara, Kanazawa University (Japan)
Toshiki Watanabe, Nagoya University (Japan)
Kengo Mochizuki, Nagoya University (Japan)
Shiho Watanabe, Nagoya University (Japan)
|
|
|
|
Lunar Radar Sounder (LRS) is an instrument onboard KAGUYA (SELENE), the Japanese first large lunar explorer launched on September 14, 2007 (JST). LRS is a FM-CW radar system using 5 MHz HF radio wave, which is expected to penetrate up to a few kilometers into the lunar surface materials. The radio wave would be reflected not only at the lunar surface but also at the lunar subsurface discontinuities where dielectric properties change abruptly, so that we can know the subsurface geologic structures of the Moon by LRS observations. The range resolution of LRS is 75 m in the vacuum, whereas the sampling interval in the flight direction is about 75 m when the KAGUYA spacecraft altitude is 100 km. Image processing techniques to enhance and detect the subsurface reflections have been developed and tested. For instance, data stacking in the flight direction could effectively suppress the random noise. Moreover, we adopted the migration technique, which is a popular method to process seismic reflection data to study subsurface geologic structures on the Earth, in order to remove hyperbolic patterns on LRS images due to strong reflections from isolated surface reflectors such as steep foreslopes of impact craters. This processing is particularly important for the LRS data of the lunar highlands, as the density of impact craters is much higher in the highlands than in maria.
Horizontal subsurface reflectors were detected at a depth of several hundreds meters in LRS data of multiple flight lines in the lunar maria such as Mare Serenitatis. They might indicate boundaries between the dense mare basalt and relatively porous eject deposits formed by a meteorite impact nearby. We compared the subsurface refection patterns on the LRS images with those reported in the interpretation of Apollo Lunar Sounder Experiment (ALSE) data obtained in 1970s. So far, we found that the depth of the horizontal reflectors in the LRS data is significantly shallower than that in the ALSE data.
|
|
|
|
|
|
|
|
|
