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Crustal and time-varying magnetic fields at the InSight landing site on Mars

Catherine L. Johnson 1, 2 Anna Mittelholz 1 Benoît Langlais 3 Christopher T. Russell 4 Véronique Ansan 3 Don Banfield 5 Peter J. Chi 6 Matthew O. Fillingim 7 François Forget 8 Heidi Fuqua Haviland 9 Matthew Golombek 10 Steve Joy 11 Philippe Lognonne 12 Xinping Liu 11 Chloé Michaut 13 Lu Pan 13 Cathy Quantin-Nataf 13 Aymeric Spiga 8, 14 Sabine Stanley 15, 16 Shea N. Thorne 1 Mark Wieczorek 17 Yanan Yu 11 Suzanne E. Smrekar 10 William B. Banerdt 14 
Abstract : Magnetic fields provide a window into a planet’s interior structure and evolution, including its atmospheric and space environments. Satellites at Mars have measured crustal magnetic fields indicating an ancient dynamo. These crustal fields interact with the solar wind to generate transient fields and electric currents in Mars’s upper atmosphere. Surface magnetic field data play a key role in understanding these effects and the dynamo. Here we report measurements of magnetic field strength and direction at the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) landing site on Mars. We find that the field is ten times stronger than predicted by satellite-based models. We infer magnetized rocks beneath the surface, within ~150 km of the landing site, consistent with a past dynamo with Earth-like strength. Geological mapping and InSight seismic data suggest that much or all of the magnetization sources are carried in basement rocks, which are at least 3.9 billion years old and are overlain by between 200 m and ~10 km of lava flows and modified ancient terrain. Daily variations in the magnetic field indicate contributions from ionospheric currents at 120 km to 180 km altitude. Higher-frequency variations are also observed; their origin is unknown, but they probably propagate from even higher altitudes to the surface. We propose that the time-varying fields can be used to investigate the electrical conductivity structure of the martian interior
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Submitted on : Monday, November 16, 2020 - 12:14:10 PM
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Catherine L. Johnson, Anna Mittelholz, Benoît Langlais, Christopher T. Russell, Véronique Ansan, et al.. Crustal and time-varying magnetic fields at the InSight landing site on Mars. Nature Geoscience, Nature Publishing Group, 2020, 13 (3), pp.199-204. ⟨10.1038/s41561-020-0537-x⟩. ⟨insu-02544796⟩



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