Periodic Reporting for period 2 - Exo-Oceans (Searching and Characterizing Extraterrestrial Subsurface Oceans)
Reporting period: 2022-04-01 to 2023-09-30
The existence of liquid water is one of the few preconditions for life as we know it. Therefore, the search and characterization of liquid water outside of Earth plays an essential role in the search for extraterrestrial life. Prominent candidates to host liquid water are moons in the outer solar system, which can maintain oceans under their icy surfaces. The currently most effective way to identify such subsurface oceans is through effects of their salinity and thus electrical conductivity. The conductivity modifies the magnetic field around these moons through a process referred to as electromagnetic induction. Spacecraft measurements of associated magnetic field perturbations provided evidence for oceans within Jupiter’s moon Europa and Ganymede. Previous analysis tools however reached an impasse. No scientific techniques were available, which provide quantitative estimates and uncertainties of key ocean properties when the effects of the dense magnetized plasmas around the moons are included. Our team searches for entirely new approaches, which overcome these issues. Our novel techniques include a simultaneous treatment of the physics in all internal and external conductive layers and use for the first time all available observations including auroral emission to go beyond considering magnetic fields only. EXO-OCEANS systematically characterizes the ocean properties on Europa and Ganymede including the ocean candidate Callisto. Characterizing the oceans on Ganymede, Europa and Callisto are at the heart of ESA’s Juice and NASA’s Europa Clipper missions. For Saturn’s moons Titan and Enceladus where currently existing techniques do not apply, we work on new detection techniques. In parallel we use the Hubble Space Telescope to search and characterize aurora in extrasolar planetary systems to pave the way for ocean detections beyond the solar system.
Our team started to establish new models of induction within the oceans of the icy moons in the outer solar system and the plasma physics occurring in the thin atmospheres and ionospheres of the moons. An unforeseen positive aspect of our research project was that NASA changed the trajectory of its Juno Spacecraft orbiting in the Jupiter system and enabled close flybys at Jupiter's moons Ganymede and Europa. Our team is very active in analyzing these new data together with previous measurements of the Galileo spacecraft and the Hubble Space Telescope. The results of the Ganymede flyby resulted in a special issue in the journal Geophysical Research Letters.
Our team is also actively involved in the search for auroral emission outside the solar system. Based on awarded Hubble Space Telescope observations, we found tentative evidence of ultraviolett aurora on a brown dwarf. We also constrained the energetics of auroral emission at radio wavelength on the most promising exoplanet believed to have its own magnetic field.
Our team is also actively involved in the search for auroral emission outside the solar system. Based on awarded Hubble Space Telescope observations, we found tentative evidence of ultraviolett aurora on a brown dwarf. We also constrained the energetics of auroral emission at radio wavelength on the most promising exoplanet believed to have its own magnetic field.
Until the end of the project, we will derive new constraints on the properties and existence of subsurface oceans within key icy moons in the outer solar system. Our team will additionally develop an understanding of the joint physical processes of electromagnetic induction within the icy moons and the electromagnetic processes driven by the plasma surrounding these moons and their thin atmospheres. With this understanding we will also generate tools which will be essential for the analysis of the upcoming measurements by ESA's JUICE and NASA's Europa Clipper spacecraft.