DIX Planetary Science Seminar

Observations made by the planetary missions have profoundly broadened our understanding of the present-day interior structures of solar system bodies and how these systems have formed and evolved. In several cases, the interiors and orbits of the planets and satellites evolve in a tightly coupled way. Therefore, by combining the astrometric and geophysical measurements, we can constrain both the present-day interior properties and long-term evolution of planetary bodies. In the case of Enceladus, the measurements obtained by Cassini suggest seafloor hydrothermal activity and a habitable subsurface ocean. However, to understand its habitability, it is essential to understand the thermal state of Enceladus and the location of the tidal heating which determine the long-term processes that can sustain conditions relevant to habitability in the ocean for sufficiently long timescales. I will present the current state of knowledge about Enceladus's interior and the geophysical measurements that are required to understand whether the large tidal heating is happening in the rocky core and can possibly power the hydrothermal activity for a long time, or alternatively is occurring in the ice shell. In addition to Enceladus, I will discuss the Mars system and use a combined thermal evolution/orbital evolution of Mars and its moons constrained by the available geophysical data to study the history of Phobos and Deimos around Mars. I will show that this method provides quantitative constraints on the age and orbits of the moons around Mars and help understand their origin. I will also show that this approach can constrain the bulk interior properties of the Martian moons. Finally, I will briefly discuss the ongoing work on the coupled interior and orbital evolution of Europa in the Laplace resonance with Io and Ganymede. I will show that the coupling between the evolution of the interiors and orbits of all moons has likely played an important role in the history of this system.