JpGU-AGU Joint Meeting 2020

Presentation information

[E] Oral

S (Solid Earth Sciences ) » S-EM Earth's Electromagnetism

[S-EM19] Earth and planetary magnetism: Observations, modeling, and implications on dynamics and evolution

convener:Hirokuni Oda(Institute of Geology and Geoinformation, Geological Survey of Japan, AIST), Futoshi Takahashi(Faculty of Sciences, Kyushu University), Courtney Jean Sprain(University of Florida), Yoichi Usui(Japan Agency for Marine-Earth Science and Technology)

[SEM19-02] Constraints on the Source of the Martian Magnetic Anomalies Inferred From Relaxation Time of Remanent Magnetization

★Invited Papers

*Masahiko Sato1, Yuhji Yamamoto2, Takashi Nishioka2, Kazuto KODAMA3, Nobutatsu Mochizuki4, Masashi Ushioda5, Ryoichi Nakada6, Hideo Tsunakawa7 (1.The University of Tokyo, 2.Kochi University, 3.Doshisha University, 4.Kumamoto University, 5.National Institute of Advanced Industrial Science and Technology, 6.Japan Agency for Marine-Earth Science and Technology, 7.Japan Aerospace Exploration Agency)

Keywords:Martian magnetic anomaly, magnetite, relaxation time of remanent magnetization

The strong magnetic anomalies observed over Mars originate from remanence of deep crust, which should be preserved during 4 billion years. We estimate the relaxation time of remanence carried by various types of magnetite, considering temperature and pressure dependences of magnetic parameters. The estimation shows that acicular-shaped single-domain magnetite is needed to retain the thick magnetized layer during 4 billion years in a low-Urey ratio scenario, whereas acicular-shaped single-domain, equidimensional single-domain, and pseudo-single-domain magnetites can be the source of anomalies in a high-Urey ratio scenario. In each case, fine-grained (<10 μm) and preferably high-aspect-ratio magnetite in deep crust is needed to explain the observed anomalies.