P052-08
Europa Magnetotelluric Sounder Characterizes Both Intrashell Water and the Deep Ocean

Friday, 11 December 2020: 17:58
Virtual
Robert E Grimm, Southwest Research Institute Boulder, Planetary Science Directorate, Boulder, CO, United States, Gregory T Delory, Heliospace Corp., Berkeley, CA, United States, Jared R Espley, Goddard Space Flight Center, Greenbelt, MD, United States and David E Stillman, Southwest Research Institute, Boulder, CO, United States
Recorded Presentation
Abstract:
Time-varying electromagnetic (EM) fields induce eddy currents in planetary interiors, which can be used to probe variations of electrical conductivity with depth. By jointly measuring magnetic and electric fields, the magnetotelluric (MT) method recovers subsurface properties using a single station, without any knowledge of source-field properties.

The high sensitivity of EM sounding to saline water enabled the discovery of the Europa subsurface ocean. However, a key Lander requirement is to detect any liquid water within 30 km, which could include dikes, sills, or diapirs within the ice shell. The Galileo measurements exploited the known structure of Jupiter’s magnetosphere as an EM source at long periods, but the geometries of short-period waves that probe within the ice shell are not known a priori. Comparison with an orbital magnetometer -- if one was available -- would be fraught with plasma distortions. MT can readily meet the objective because it has high bandwidth, does not require an orbital magnetometer, and is largely immune to plasma distortion. Sensitivity to water is much better than seismology and the measurements can be completed in a few days. Radiation tolerance is readily met by spot-shielding the electric-field op amps and by enclosing the central electronics in the Lander vault. The fluxgate magnetometer sensor needs no shielding because it has no active electronic parts.

We have completed a TRL 6 prototype for a Europa Magnetotelluric Sounder (EMS) under NASA COLDTech sponsorship. This system comprises central electronics, remote-deployed electrodes, and a magnetometer on a mast. We performed functional data-acquisition testing and separately tested the deployments under Europa conditions. This prototype is the basis for a new effort under ICEE-2, a pool of instruments selected for Lander development. The EMS design has already been ported to a Lunar Magnetotelluric Sounder that has been selected for flight under the CLPS program.

<< Previous Abstract | Next Abstract