Interior Characterization of Europa using Magnetometry (ICEMAG): Probing the Europan Ocean and Exosphere

Abstract:

Magnetic induction is a powerful tool for probing the subsurface. The magnetometer on the Galileo mission to Jupiter found compelling evidence for subsurface oceans on Europa, Ganymede and Callisto; however, the single induction frequency measured did not allow characteristics of the ocean to be discerned. The Interior Characterization of Europa using MAGnetometry (ICEMAG) instrument, selected for NASA’s Europa mission payload in May 2015, is designed to measure Europa’s induction response at multiple frequencies with high accuracy. ICEMAG definitively assesses the ice shell thickness, and the conductivity and thickness of the subsurface ocean. This knowledge informs models of Europa’s thermal evolution and allows evaluation of processes that have cycled material between the depths and the surface. Magnetic field measurements also determine the electrical currents associated with coupling of plumes to the corotating magnetospheric plasma and coupling of Europa to the Jovian ionosphere. ICEMAG utilizes UCLA fluxgate magnetic field sensors as well as JPL helium sensors in an integrated magnetic measurement system. The advent of laser-pumped helium sensors and advances in digital signal sampling enables an innovative multi-sensor magnetometer to be flown that is able to monitor spacecraft fields and maintain absolute accuracy of the measurement at a level of ~1 nT over time scales of years, without special maneuvers such as spacecraft rolls.