Shoko Oshigami¹, Shiho Watanabe², Yasushi Yamaguchi², Atsushi Yamaji³, Takao Kobayashi⁴, Atsushi Kumamoto⁵, Ken Ishiyama⁵ and Takayuki Ono⁵

¹National Astronomical Observatory of Japan, Oshu, Japan
²Graduate School of Environmental Studies, Nagoya University, Chikusa-ku, Japan
³Graduate School of Science, Kyoto University, Kyoto, Japan
⁴Geological Research Division, Korean Institute of Geoscience and Mineral Resources, Daejeon, South Korea
⁵Graduate School of Science, Tohoku University, Sendai, Japan

The Lunar Radar Sounder (LRS) onboard Kaguya (SELENE) detected widespread horizontal reflectors under some nearside maria. Previous studies estimated that the depths of the subsurface reflectors were up to several hundreds of meters and suggested that the reflectors were interfaces between mare basalt units. The comparison between the reflectors detected in the LRS data and surface age maps indicating the formation age of each basalt unit allows us to discuss the lower limit volume of each basalt unit and its space and time variation. We estimated volumes of basalt units in the ages of 2.7 Ga to 3.8 Ga in the nearside maria including Mare Crisium, Mare Humorum, Mare Imbrium, Mare Nectaris, Mare Serenitatis, Mare Smythii, and Oceanus Procellarum. The lower limit volumes of the geologic units estimated in this study were on the order of 10³ to 10⁴ km³. This volume range is consistent with the total amount of erupted lava flows derived from numerical simulations of thermal erosion models of lunar sinuous rille formation and is also comparable to the average flow volumes of continental flood basalt units formed after the Paleozoic and calculated flow volumes of Archean komatiite flows on the Earth. The lower limits of average eruption rates estimated from the unit volumes were on the order of 10⁻⁵ to 10⁻³ km³/yr. The estimated volumes of the geologic mare units and average eruption rate showed clear positive correlations with their ages within the same mare basin, while they vary among different maria compared within the same age range.

Reference
Oshigami S, Watanabe S, Yamaguchi Y, Yamaji A, Kobayashi T, Kumamoto A, Ishiyama K, and Ono T (in press) Mare volcanism: Reinterpretation based on Kaguya Lunar Radar Sounder data. Journal of Geophysical Research: Planets
[doi:10.1002/2013JE004568]
Published by arrangement with John Wiley & Sons

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