Japan Geoscience Union Meeting 2015

Presentation information

International Session (Oral)

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

[P-PS03] Rotation, inner dynamics and variations of natural processes on the Earth, the Moon and Mars.

Thu. May 28, 2015 2:15 PM - 4:00 PM A03 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Yury Barkin(Sternberg Astronomical Institute, Moscow State University, Moscow), Hideo Hanada(RISE Project, National Astronomical Observatory), Koji Matsumoto(RISE Project Office, National Astronomical Observatory), Mikhail Barkin(Moscow Aviation Institute), Chair:Yury Barkin(Sternberg Astronomical Institute,)

2:30 PM - 2:45 PM

[PPS03-02] Strong tidal heating inside an ultralow-viscosity zone over the lunar core-mantle boundary

*Yuji HARADA1, Sander GOOSSENS2, Koji MATSUMOTO3, Jianguo YAN4, Jinsong PING5, Hirotomo NODA3, Junichi HARUYAMA6 (1.SSI, MUST, 2.CRESST, UMBC, 3.NAOJ, NINS, 4.LIESMARS, WHU, 5.NAOC, CAS, 6.ISAS, JAXA)

Keywords:the Moon, core-mantle boundary, low-viscosity zone, tidal heating

Tidal heating due to viscous dissipation in a planetary body is an important energy conversion process, depending on its internal structure, and connected to its thermal and orbital states. Our moon is not an exception. Previous studies have calculated the tidal response including dependence of the dissipation on the lunar interior structure, but these studies did not completely explain the geodetically-observed dependence of the dissipation on the lunar tidal period. One possibility to interpret this frequency-dependence is a low-viscosity layer inside the mantle as a natural consequence of the strong seismic attenuation zone, because such a viscosity contrast affects this dependence. However, previous studies have not considered its potential impact. Here we show that the explicit influence of the low-viscosity zone successfully provides the frequency-dependent dissipation on the Moon consistent with the geodetic observables. We found that the above-mentioned high attenuation zone is equivalent to the low-viscosity layer. Furthermore, we also found that the resultant viscosity value is remarkably low, signifying a relaxation time close to the tidal period. This ultralow viscosity implies partial melting as formerly suggested. Our result demonstrates that the most effective dissipation is localised to this layer, indicating a blanket effect on the core. We anticipate that such tidal heating, balanced against convective cooling, maintains this layer over the course of the lunar tidal history.