Our research interests have been primarily in understanding the physical
processes that control the evolution of terrestrial planets
(Earth, Moon, Mars, ...). Modern space exploration has provided high
resolution gravity and topography data about many planets. Other observational
techniques including seismology and in-situ sampling have revealed the
structure and composition of planetary interiors (primarily for Earth and
its Moon, but soon for Mars as well). Understanding the physical processes
that are responsible for these observations and how they are related to
thermal evolution of planets is our primary goal of research. Because
the planetary dynamics depend on how a planet responds to forces
(i.e., a material property called the rheology), another major aspect of
our research is to understand
the rheological properties of Earth's materials.
Thermal convection in planetary mantles is the most important physical
process that controls the dynamics of terrestrial planets. Mantle convection
determines the thermal structure in the mantle that has been revealed in
seismic images, controls the distribution of heat release at the surface (volcanoes and
seafloor spreading) and surface topography (mountain ranges and ocean basins),
dictates the large-sclae horizontal movement of surface
crust (i.e., plate tectonics for Earth), and ultimately governs the thermal
evolution of planets (from shortly after their formation to ...).
To study the dynamics of mantle convection and its surface manifestation,
we use both instability analyses and numerical simulation in our research.
Recently, building upon our previous studies on global mantle flow,
we have focused our effort on understanding interaction of
convection at multiple scales, i.e., the global scale associate with plate
motion and the small-scale associated with thermal plumes. This problem
has important implications to the heat transfer within the mantle and the
style of mantle convection.
We work closely with our global seismology group at CU (Mike Ritzwoller) to understand the
seismic images of the mantle from the viewpoint of mantle dynamics.
Another ongoing project is to understand the mantle rheology by examining
the vertical motion of Earth's surface. In collaborating with Watts (Oxford),
we have inferred the activation energy, one of the most important deformational
properties for mantle materials, by using the observed flexural rigidity near
seamounts. While we continue to make progress on this project, we recently
started to study another closely related important problem on mantle rheology
-- the influence of inhomogeneous mantle rheological structure on the
vertical motion of Earth's surface since the last deglaciation (collaborating
with John Wahr at CU).
Our research on other terrestrial planets at the moment is primarily on understanding
the long-wavelength topography and gravity on the Mars and their implications
for thermal evolution of the Mars. In particular, we are interested in
the mechanisms responsible for the formation of the crustal dichotomy and
Tharsis rise (a volcanoic province occupying 1/4 of Mars surface). In addition
to studies on the Mars, we
continue our studies on the lunar evolution (with Marc Parmentier of Brown Univ.).
I also have strong interests in high performance computing and numerical
analysis. In working with scientists at Caltech (Gurnis) and CSIRO of Australia
(Moresi), I have developed 3D full multigrid spherical finite element models of mantle
(see an example of how a
planet is cut to fit to parallel computers. Here is
for multigrid ).
With funding from NSF and CU, we have built a mid-sized PC-cluster (48 Pentium
III processors with 48 Gbytes
RAM) to run our applications. We also have access to parallel supercomputers
at NSF supercomputer centers (through NPACI).
Our research is supported by the NSF, NASA, and David and Lucile Packard Foundation.