Liquid water seems to play a crucial role in the evolution of dwarf planets. Despite their small sizes and cold surface temperatures, Kuiper Belt Objects(KBOs) such as Charon bear evidence for subsurface liquid water and aqueous chemistry products brought to the surface. How could water remain liquid? Is it still there? Thermal models of KBOs have shown that they are capable of sustaining subsurface liquid water by radiogenic heating, despite frigid surface temperatures. Subsurface liquid is predicted to persist for many Gyr on bodies as small as Charon (radius 600 km). These models are broadly applicable to many other large KBOs or dwarf planets, including Ceres (which has been suggested to have formed together with KBOs in the outer solar system). But the models currently deal only with the geophysics of dwarf planets' internal structure and thermal evolution. Geochemistry will also play a significant role in dwarf planet evolution and feedback into the geophysics. Geochemical processes have not been considered in thermal models of dwarf planets. These assume that antifreezes like ammonia remain in the subsurface liquid for many Gyr, despite predictions of time-independent geochemical models that ammonia could form ammonium salts, less efficient antifreezes, or oxidize to N2. The modification of rock thermal properties (e.g., thermal conductivity) upon hydration is another prime example of how geochemistry must be coupled to geophysics, to investigate dwarf planet evolution and liquid persistence. To address these questions, we propose to: 1. Model the types of fluid flow on small bodies: (a) quantify convection-driven hydrothermal circulation through a permeable core, cracked from thermal contraction; and (b) analytically determine the conditions required to initiate cryovolcanism. 2. Use available geochemical codes to model abundances of species in the subsurface fluid, including temperature and chemistry as fluid rises to the surface, and minerals produced by water-rock interaction, to produce a geochemistry subroutine to be used in thermal evolution codes. 3. Predict internal structure and chemistry of dwarf planets, and composition of material carried to their surface, and enhance science return from New Horizons at Charon (and also Dawn at Ceres) in 2015. Our modeling effort represents a significant advance in the coupling between geophysics and geochemistry in dwarf planets. Our predictions of salt and hydrated mineral abundances on the surfaces of small icy bodies, for different outcomes of origin and evolution scenarios, will allow us to probe the formation and internal evolution of dwarf planets.
|Effective start/end date||8/28/14 → 8/27/18|
- NASA: Goddard Space Flight Center: $236,306.00