Science Seminars

Magnetic field sounding of Europa’s ocean: Using plasma physics for oceanography

Speaker: Frank Crary (LASP)
Date: Thursday, Feb 08, 2018
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

Jupiter’s moon, Europa is believed to have a liquid water ocean below its icy surface. One of the strongest lines of evidence for this is an induced magnetic field signature observed by the Galileo spacecraft. But the Galileo observations are limited and only sufficient to establish the existence of an ocean (or, strictly speaking, a sub-surface, electrically conductive layer.) Extracting the properties of this ocean, such as thickness, depth or salinity, is much more difficult. Currently, two planned missions, the European JUICE spacecraft and NASA’s Europa Clipper, will attempt such investigations. A key difficulty will be the effects of Europa’s interaction with Jupiter’s magnetosphere. Europa’s tenuous atmosphere is sufficient to conduct electric currents and deflect the flow of the background plasma. In the process, this interaction generates magnetic field perturbations. These perturbations are the largest obstacle to probing Europa’s oceans through magnetic sounding. While this has been appreciated for many years, and a better understanding of the plasma interaction is clearly required. But there has been relatively little, systematic work on how, exactly, to apply a better understanding of the interaction to improving knowledge of the subsurface ocean. In this presentation, I will summarize our current understanding of ocean and its magnetic signature, describe how improved measurements can tell us more (and how accurate they must be to do so), our understanding and models of the plasma interaction, and describe how they can be used to separate the plasma perturbations from the ocean signature. Finally, I will suggest how a similar approach could be used to investigate other, suggested “ocean worlds” such as Titan and Triton.