Detectability of Local Water Reservoirs in Europa's Surface Layer Under Consideration of Coupled Induction

• Published in: Journal of geophysical research. Planets Vol. 128; no. 10
• Main Authors: Winkenstern, Jason, Saur, Joachim
• Format: Journal Article
• Language: English
• Published: 01.10.2023
• Subjects: Europa; induction; interior
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2023JE007992

The icy moon Europa is a primary target for the study of ocean worlds. Its subsurface ocean is expected to be subject to asymmetries on global scales (tidal deformation) and local scales (chaos regions, fractures). Here, we investigate the possibility to magnetic sound local asymmetries by calculating the induced magnetic fields generated by a radially symmetric ocean and a small, spherical water reservoir between the ocean and Europa's surface. The consideration of two conductive bodies introduces non‐linear magnetic field coupling between them. We construct an analytical model to describe the coupling between two conductive bodies and calculate the induced fields within the parameter space of possible conductivity values and icy crust thicknesses. Given the plasma magnetic field perturbations, we find that a reservoir cannot be detected during a flyby at 25 km altitude using electromagnetic induction. Potential detection of liquid water reservoirs can be achieved by deploying magnetometers on Europa's surface, where one magnetometer is placed directly on the target region of interest and a second one in the nearby vicinity as reference to distinguish from global asymmetries. With this method, the smallest reservoir that can be detected has a radius of 8 km and a conductivity of 30 S/m. Larger reservoirs are resolvable at lower conductivities, with a 20 km reservoir requiring a conductivity of approximately 5 S/m. Plain Language Summary Jupiter's icy moon Europa most likely harbors an ocean of liquid salt‐water underneath its icy surface. In addition, small reservoirs of liquid water might exist within Europa's icy crust at very shallow depths. Such features offer interesting target regions for future lander missions in the search for extraterrestrial life, for which Europa has been a primary target. One possibility to infer the ocean's properties is electromagnetic sounding. This method makes use of the magnetic fields induced by Jupiter's background field, which can be modeled and compared to magnetic field measurements performed by satellite missions. Here, we present a model in which we implement a local water reservoir between the surface and the ocean and calculate the magnetic fields that are induced in both reservoir and ocean. Here, we consider the electromagnetic coupling interaction that takes place between the two water bodies. We investigate if reservoirs can be detected in magnetic field measurements performed with the Europa Clipper spacecraft, as well as with magnetometers deployed on Europa's surface. The potential detection of liquid water reservoirs could provide insights into the processes inside Europa's icy shell, for example, the formation of chaos regions visible on Europa's surface. Key Points An analytical model for the mutual self‐consistent induction of an ocean and a local, spherical water reservoir has been developed During a flyby at 25 km altitude, liquid water reservoirs within Europa's icy crust cannot be detected with magnetometer measurements A reservoir can be detected with one magnetometer on the surface directly above the reservoir and a second surface magnetometer nearby