Galilean Satellites
The Galilean satellites form a fascinating solar system in miniature, from fiery Io to icy Callisto. Thanks to the Galileo spacecraft, we now have enough data to start to unravel their interior structures and histories. I have particularly made use of surface topography to infer the rigidity of the surface, and hence heat fluxes on both Ganymede and Europa. Heat fluxes are important because they tell us about the thermal evolution of the satellites, and also how their orbits may have changed over time. I have also thought about the way in which specific geological features form, such as bands or domes on Europa. A recent piece of work may help to explain the puzzling and long-standing observation that extension is much more common than compression on the outer Galilean satellites. Finally, Bob Pappalardo and I are currently writing a long review article on the physics of the icy Galilean Satellites.
These images show that bands on Europa
are higher than their surroundings. Why? One possibility is that they
formed recently, and are still warm, but it is more likely that they are
lighter than the surroundings because of compositional differences.
PhD Opportunities (click here for more details)
There are a large number of projects that I am interested in pursuing, of which two are particularly suitable for graduate students. One is investigating the extent to which compositional convection, as opposed to thermal convection, may be responsible for surface features such as domes and bands. Compositional convection is a strong contender because it can generate larger stresses, and thus bigger topography, than thermal convection, but very little work has been done on it in the icy satellite context.
The other project is using newly-obtained topography to investigate surface processes on the icy satellites. For instance, by looking at how the topographic power varies with wavelength, we can assess the wavelength range over which processes such as erosion or mass-wasting are important, and thus infer the rate at which the surface is being modified. Nobody has yet tried this for the icy satellites, though similar efforts are underway on Mars.
Publications
Here is a list of Galilean satellite-related topics I have published or submitted:
· Furrow flexure and ancient
heat flux on Ganymede, F. Nimmo and R.T. Pappalardo, Geophys. Res. Lett.
, in press. Preprint
· Stresses generated in cooling
viscoelastic ice shells: Application to Europa, F. Nimmo, J. Geophys.
Res. , in press. Preprint
· Non-Newtonian topographic
relaxation on Europa, F. Nimmo, Icarus , 168, 205-208, 2004 Reprint
· Dynamics of rifting and
modes of extension on icy satellites, F. Nimmo, JGR 109,
E01003, 2004 (PDF
file available)
· On the origins of band
topography, Europa, F. Nimmo, R.T. Pappalardo and B. Giese, Icarus 166,
21-32, 2003 (PDF
file available).
· Estimates of Europa's ice
shell thickness from elastically-supported topography, F. Nimmo, B. Giese
and R.T. Pappalardo, Geophys. Res. Lett. 30(5), 1233,
10.1029/2002GL016660, 2003 (PDF file
available)
· Causes, characteristics and
consequences of convective diapirism on Europa, F. Nimmo and M. Manga, Geophys.
Res. Lett. 29(23), 2109, 10.1029/2002GL015754, 2002 (PDF file
available).
· Thermal consequences of
strike-slip motion on Europa, F. Nimmo and E. Gaidos, J. Geophys. Res. ,
107(E4), 5021, 10.1029/2000JE001476, 2002. (PDF file
available)
· Elastic thickness and heat flux
estimates on Ganymede, F. Nimmo, R.T. Pappalardo and B. Giese, Geophys.
Res. Lett., 29(7), 1158, 10.1029/2001GL013976, 2002. (PDF file
available)
· Tectonics and water on Europa, E. Gaidos and F. Nimmo, Nature 405, 637, 2000. (abstract here PDF file (124K) available).
Department of Earth and Spaace Sciences home page
Last Modified: 18 Oct 2004.