UC Santa Cruz

The evolution of a planetary body often determines and is determined by its thermal properties. In my first project, I explore the consequences of heating upon pore closure, allowing me to estimate the heat flow through the Martian crust during the latest significant pore generation event—likely large basin-forming impacts. We apply a pore closure model developed for the Moon to Mars and take into account the geological processes that may alter the depth of a transition between porous and competent crust. If the 8–11 km deep discontinuity in seismic wave speed detected by the InSight lander marks the base of the uppermost porous layer of the Martian crust, then the heat flux at the time the porosity was created must exceed 60 mW m^−2, indicating a time prior to 4 Ga. Then, I explore how the global shape of an icy satellite allows us to infer its heat budget and interior—including the presence or absence of a subsurface global ocean. I apply this method in my second and third projects to Tethys and Mimas, respectively. We assume spatial variations in tidal heating are responsible for thickness or temperature variations in an isostatic ice shell, which manifests as surface topography. For Saturn’s moon Tethys, our best-fit models require Pratt isostasy and obliquity tides, with a normalized moment of inertia 0.340-0.345 and an average surface heat flux 1-2 mW m^−2. Then, we find that to account for its hydrostatic shape, Mimas’ normalized moment of inertia is 0.375, indicating a relatively undifferentiated world. Its remaining topography is consistent with a ∼30 km thick conductive ice shell in Airy isostasy atop a weakly convecting ∼30 km thick layer that itself mantles a ∼140 km radius ice-rock interior. For neither satellite do we find an ocean. However, the total power and pattern inferred to produce both satellites’ shapes from tidal heating indicate an ancient era of high obliquity. The common thread of all three projects is the flow of heat, and how our understanding of it can be revealed by or can reveal properties of the planetary bodies we study.