Amy Courtright Barr

Learn More
[1] At the temperatures and stresses associated with the onset of convection in an ice I shell of the Galilean satellites, ice behaves as a non-Newtonian fluid with a viscosity that depends on both temperature and strain rate. The convective stability of a non-Newtonian ice shell can be judged by comparing the Rayleigh number of the shell to a critical(More)
Heat transport across Europa's ice shell controls the thermal evolution of its interior and provides a source of energy to drive resurfacing. Recent improvements in knowledge of ice rheology, the behavior of convection, and the interaction between convection and lithospheric deformation have led to more realistic and complex models of the geodynamics of(More)
The volume of melt produced in hypervelocity planetary impacts and the size and shape of the melted region are key to understanding the impact histories of solid planetary bodies and the geological effects of impacts on their surfaces and interiors. Prior work of Pierazzo et al. gave the first estimates of impact melt production in geological materials(More)
The onset of convection in the power-law creep regime on the terrestrial planets and icy satellites is poorly constrained. The major difficulty is that the viscosity of power-law fluids approaches infinity when the perturbation amplitudes approach zero and thus the methods of linear theory are inapplicable. Here, we determine the critical Rayleigh number(More)
Introduction: Numerical simulations of solid-state convection in Europa's ice shell have so far been limited to consideration of Newtonian flow laws, where the viscsoity of ice is strongly dependent upon temperature, predicting that a stagnant lid should form at the top (10-40%) of a convecting ice shell [1, 2]. Such large thicknesses seem to contradict(More)
[1] Observations of Enceladus by the Cassini spacecraft indicate that this tiny Saturnian moon is geologically active, with plumes of water vapor and ice particles erupting from its southern polar region. This activity suggests that tidal dissipation has become spatially localized, perhaps due to a compositional, rheological, and/or thermal anomaly in its(More)
[1] Ice I exhibits a complex rheology at temperature and pressure conditions appropriate for the interiors of the ice I shells of Europa, Ganymede, and Callisto. We use numerical methods and existing parameterizations of the critical Rayleigh number to determine the conditions required to trigger convection in an ice I shell with each of the stress-,(More)
1 and a large rock/metal core 2 , whereas Callisto's surface shows no sign of resurfacing 3 and the separation of ice and rock in its interior seems incomplete 2. These differences have been difficult to explain 4–11. Here we present geophysical models of impact-induced core formation to show that the Ganymede–Callisto dichotomy can be explained through(More)
Accretional temperature profiles for Saturn's large moon Titan are used to determine the conditions needed for accretion to avoid global melting as a function of the timing, duration, and nebular conditions of Titan's accretion. We find that Titan can accrete undifferentiated in a ''gas-starved " disk even with modest quantities of ammonia mixed in with its(More)