Japan Geoscience Union Meeting 2015

Presentation information


Symbol P (Space and Planetary Sciences) » P-PS Planetary Sciences

[P-PS23] Lunar science and exploration

Tue. May 26, 2015 11:00 AM - 11:45 AM A02 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Hiroshi Nagaoka(Waseda Univ.), Tomokatsu Morota(Graduate School of Environmental Studies, Nagoya University), Masaki N Nishino(Solar-Terrestrial Environment Laboratory, Nagoya University), Chikatoshi Honda(The University of Aizu), Yuichiro Cho(Department of Physics, Rikkyo University), Chair:Makiko Ohtake(宇宙航空研究開発機構 宇宙科学研究本部 固体惑星科学研究系), Yoshiko Ogawa(The University of Aizu)

11:30 AM - 11:45 AM

[PPS23-22] Magnetic anomalies, dynamo and true polar wander of the Moon

*Futoshi TAKAHASHI1, Hideo TSUNAKAWA2, Hisayoshi SHIMIZU3, Hidetoshi SHIBUYA4, Masaki MATSUSHIMA2 (1.Department of Earth and Planetary Sciences, Kyushu University, 2.Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 3.Earthquake Research Institute, University of Tokyo, 4.Department of Earth and Environmental Sciences, Kumamoto University)

Keywords:magnetic anomaly, dynamo, core, polar wander

Applying the latest advanced paleomagnetic technique to the Apollo samples, it is now well established that the Moon once had an ancient core dynamo operated from 4.2 to 3.56 billion years ago, or even younger age. Because these results are based on paleointensity retrieved from unoriented samples, any directional information cannot be obtained. Instead, we focus on the magnetic anomalies on the Moon. Since the magnetization of the lunar crust in the magnetic anomalies could be records of an early core dynamo of the Moon, the magnetic anomalies may yield directional information of the lunar paleomagnetic field. Here we present results of our global survey of magnetic anomalies on the lunar surface using magnetometer data acquired by the Lunar Prospector and Kaguya spacecraft. Using an iterative inversion method, we extract magnetization vectors from well-isolated magnetic anomalies and derive the positions of paleomagnetic poles. We find two distinct clusters of the resultant paleomagnetic poles: one near the present rotation axis and the other at mid-latitude (Takahashi et al., 2014). The result is consistent with a dipole-dominated lunar magnetic field generated by a core dynamo that was reversing the polarity. It is also implied that the Moon experienced a polar wander event. Additional inversion results for well-isolated central magnetic anomalies based on the surface vector mapping method (Tsunakawa et al., 2014) suggest existence of the third cluster of the lunar magnetic pole.

Takahashi, F., H. Tsunakawa, H. Shimizu, H. Shibuya, and M. Matsushima (2014), Reorientation of the early lunar pole, Nature Geosci., 7, 409-412, doi:10.1038/ngeo2150.
Tsunakawa, H., H. Shibuya, F. Takahashi, H. Shimizu, and M. Matsushima (2014), Regional mapping of the lunar magnetic anomalies at the surface: Method and its application to strong and weak magnetic anomaly regions, Icarus, 228, 35-53, doi:10.1016/j.icarus.2013.09.026.