TY - JOUR

T1 - Crustal and time-varying magnetic fields at the InSight landing site on Mars

AU - Johnson, Catherine L.

AU - Mittelholz, Anna

AU - Langlais, Benoit

AU - Russell, Christopher T.

AU - Ansan, Véronique

AU - Banfield, Don

AU - Chi, Peter J.

AU - Fillingim, Matthew O.

AU - Forget, Francois

AU - Haviland, Heidi Fuqua

AU - Golombek, Matthew

AU - Joy, Steve

AU - Lognonné, Philippe

AU - Liu, Xinping

AU - Michaut, Chloé

AU - Pan, Lu

AU - Quantin-Nataf, Cathy

AU - Spiga, Aymeric

AU - Stanley, Sabine

AU - Thorne, Shea N.

AU - Wieczorek, Mark A.

AU - Yu, Yanan

AU - Smrekar, Suzanne E.

AU - Banerdt, William B.

PY - 2020/3/1

Y1 - 2020/3/1

N2 - 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.

AB - 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.

U2 - 10.1038/s41561-020-0537-x

DO - 10.1038/s41561-020-0537-x

M3 - Journal article

AN - SCOPUS:85081097062

VL - 13

SP - 199

EP - 204

JO - Nature Geoscience

JF - Nature Geoscience

SN - 1752-0894

IS - 3

ER -