Research Interests
I am primarily interested in the global-scale problems concerning the terrestrial planets and icy moons of the solar system. I wish to understand the physical processes that control the evolution of these objects. I focus on geodynamic approaches to these problems, such as mantle convection, elastic flexure, and viscoelastic relaxation. My goal is to look at the big picture; to understand why the planets and moons look the way they do, what they were like early in their history, and how they evolved to their present state.
My research falls in the realm of Planetary Geodynamics. Geodynamics is the study of the internal movements of the Earth. It involve processes such as mantle convection, tectonics, and deformation of earth materials. We need to consider rheology (material properties), heat transfer, and even the gravitational and geoid response to all these internal dynamics. Although most geodynamicists study the earth, I investigated these processes in the context of other planetary bodies, particularly Mars and Enceladus, a moon of Saturn.
I'm in the Earth and Planetary Sciences department at the University of California at Santa Cruz, working with Francis Nimmo who can sometimes be difficult to find.
Here is a pdf version of my Curriculum Vita. A list of publications with links to pdfs can be found at the bottom of the page.
These are some of the specific projects I've been working on. I've given just a brief summary below. For more information on any topic, click on the title to be taken to another page dedicated to that project.
Enceladus: Tidal Dissipation, Subsurface Oceans and the South Polar Thermal Anomaly
Recently, I've been working on 3D tidal heating and convection models for icy satellites. In particular, I've been focusing on Enceladus (en-SEH-la-dus), a small-to-medium size moon of Saturn. The satellite is named after a giant in ancient Greek mythology, believed to be buried under Mt. Aetna. If you use the Italian pronunciation, you get "en-che-LA-dus", hence the image to the right.
Enceladus is a particularly interesting target, given the south polar thermal anomaly, showing massive heat flux and vapor escape from a world thought to be dead before Cassini arrived, and shattered that image like an Iron Hammer of the Apostles. The popular idea at the moment is that orbital energy from Enceladus' eccentric orbit about Saturn is being dissipated as heat in the ice shell. But is tidal heating sufficient to explain the observations? And are there other ways of doing it? That's what I'm testing.
Large-scale structures on Mars: The Hemispheric Dichotomy and the Tharsis Rise.
My recently finished thesis work focussed on Martian Geodynamics.
I find this field so interesting, because we can answer important first-order questions about the shape of Mars. Why is there a hemispherical dichotomy? Why is it oriented north-south? Why is Tharsis so big? How active was the planet
in the past? Topography and gravity data from the many spacecraft missions are the primary observations we can use to study these problems. I developed theoretical and computational models to explain these observations. Just by looking at the MOLA topography map below, you can tell that something is up.

Courtesy: NASA/GSFC
Impact heating and planetary dyanmos
Refereed Publications
Published papers
- Roberts, J.H. and F. Nimmo (2008), Near-surface heating on Enceladus and the south polar thermal anomaly, Geophys. Res. Lett. 35, L09201, doi:10.1029/2008GL033725.
- Roberts, J.H. and F. Nimmo (2008), Tidal heating and the long-term stability of a subsurface ocean on Enceladus, Icarus 194, 675-689.
- Zhong, S., N. Zhang, Z. Li, and J.H. Roberts (2007), Supercontinent cycles, true polar wander, and very long-wavelength mantle convection, Earth Planet. Sci. Lett. 261, 551-564.
- Roberts, J.H. and S. Zhong (2007),
The cause for the north-south orientation of the crustal dichotomy and the
equatorial location of Tharsis on Mars, Icarus. 190, 24-31,
doi:10.1016/j.icarus.2007.03.002.
- Roberts, J.H. and S. Zhong (2006), Degree-1 convection in the
Martian
mantle and the origin of the hemispheric dichotomy, J. Geophys.
Res., 111, E06013, doi:10.1029/2005JE002668.
- Roberts, J. H. and S. Zhong (2004), Plume-induced
topography and geoid anomalies and their implications
for the Tharsis rise, J. Geophys. Res., 109,
E03009, doi:10.1029/2003JE002226.
- Zhong, S. and J. H. Roberts (2003), On
the support
of the Tharsis rise on Mars, Earth Planet. Sci. Lett. 214,
1-9.
Conference Proceedings and Abstracts
- Roberts, J. H. and F. Nimmo (2008), Near-surface heating on Enceladus and the south polar thermal anomaly, Lunar Planet. Sci. Conf. XXXIX, 1481.
- Roberts, J. H., R. J. Lillis, M. Manga, and H. V. Frey (2008), Impact-related heating and the cessation of the Martian dynamo: Early Results. Lunar Planet. Sci. Conf. XXXIX, 1358.
- Roberts, J. H. and F. Nimmo (2007), The effect of near-surface heating on the underlying convection pattern with application to Enceladus, Eos Trans. AGU, 88 (52), Fall Meet. Suppl. Abstract P21B-0539.
- Roberts, J. H. and F. Nimmo (2007), Long-term stability of a Subsurface Ocean on Enceladus, Workshop on Ices Oceans and Fire: Satellites of the Outer Solar System, 1357.
- Roberts, J. H. and F. Nimmo (2007), Stability of a Subsurface Ocean on Enceladus, Lunar Planet. Sci. Conf. XXXVIII, 1429.
- Roberts, J. H. and S. Zhong (2006), The cause for the north-south
orientation of the crustal dichotomy and the equatorial location of Tharsis
on Mars, Eos Trans. AGU, 87 (52), Fall Meet. Suppl. Abstract P31C-0155.
- Roberts, J. H. and S. Zhong (2006), Degree-1
Mantle Convection and the Origin of the Martian Hemispheric Dichotomy,
Lunar Planet. Sci. Conf. XXXVII, 1447.
- Roberts, J. H. and S. Zhong (2006), Polar Wander of Mars Driven by
Degree-1 Mantle Convection and Its Implications for the Formation of
the Crustal Dichotomy and the Tharsis Rise, Lunar
Planet. Sci. Conf. XXXVII, 1206.
- Roberts, J. H. and S. Zhong (2005), Degree-1
Mantle Convection and the Origin of the Martian Hemispheric Dichotomy,
Lunar Planet. Sci. Conf. XXXVI, 1399.
- Roberts, J. H. and S. Zhong (2005), Crustal
Relaxation and Its Implications for the Martian Crustal Dichotomy, Lunar
Planet. Sci. Conf. XXXVI, 2170.
- Roberts, J. H. and S. Zhong (2004), Degree-1
Mantle Convection as a Process for Generating the Martian Hemispheric
Dichotomy, Workshop on Hemispheres Apart: The Origin and
Modification of the Martian Crustal Dichotomy, 4028.
- Roberts, J. H. and S. Zhong (2004), Plume-Induced
Topography and Geoid Anomalies and Their Implications for the Tharsis
Rise on Mars, Lunar Planet. Sci. Conf. XXXV, 1125.
- Roberts, J. H., E. R. Craine, and M. S. Giampapa (2001), Photometric
Monitoring of M67 with the GNAT 0.5-m Telescope, AAS 197,
40.04.