2010 Annual Research Report

Dr. Han has been performing numerical simulations of tidal oscillatory process using finite element code Tekton and solve the coupled thermal evolution equations using finite element code Conman implementing non-Newtonian grain-size-sensitive (GSS) creep rheology in two-dimensional Cartesian geometry. Their simulations show that tidal dissipation resulting from heterogeneous temperature can have a strong impact on onset of thermal convection in Europa's ice shell. With tidal dissipation included, thermal convection can occur in Europa's ice shell with ice shell thickness of 20-40 km by  grain boundary sliding (GBS) creep rheology.

Dr. Han performs numerical simulations in 3D spherical geomotry to study the dichotomy of thermal convection in Enceladus' ice shell using temperature-dependet viscosity. By implementing a weak south pole (with a viscosity contrast of 10^2-10^3 south of 45 S latitude) and ice grain size of <2-3 mm, thermal convection exhibits a strong dichotomy in Enceladus' ice shell. The south polar region experiences a strong plume reaching to the surface, and locally high heat flux, while other regions develop stagnant-lid convection or do not convect. Our results can help to explain the elevated heat flux at the south polar region on Enceladus.

Papers:

Han, L., and A.P. Showman 2010. Coupled convection and tidal dissipation in

Europa's ice shell using non-Newtonian grain-size-sensitive (GSS) creep

rheology. Icarus, doi:10.1016/j.icarus.2010.11.034.

Han, L., and A.P. Showman 2010. Coupled Convection and Tidal Dissipation 

in Europa's Ice Shell. Icarus, doi:10.1016/j.icarus.2009.12.028.

Abstracts:

Han, L., and A.P. Showman 2010. Coupled convection and tidal dissipation in

Europa's ice shell (II): non-Newtonian Viscosity. Lunar and Planetary Science

Conference 2010.

Han, L., and H.J. Melosh 2010. Origin of Europa's ridges by  

incremental ice-wedging. AGU fall meetiong.