Principal Investigator J Perron
One of the most exciting developments in geomorphology is the acquisition of imagery and topography for planetary surfaces. We use spacecraft observations, experiments, and simple models based on terrestrial theory to constrain the rates and histories of processes that shape planetary landscapes, especially processes driven by water or other liquids.
(*) Rainfall and rivers on Titan -- Titan, Saturn's largest moon, may be the only other solar system body with active rivers on its surface. In a recent analysis of the morphology of valley networks near the Huygens probe landing site, we found evidence that the valleys were incised by surface runoff, and calculated that the minimum methane rainfall rates required to form these features was similar to storms on Earth. Currently, Graduate students Ben Black and Yodit Tewelde, in collaboration with Devon Burr (U. Tennessee), are mapping drainage networks on Titan and using landscape evolution models to constrain the extent to which fluvial erosion has shaped the moon's surface.
(*) Paleoclimate records in the Martian polar caps -- Layered deposits of ice and dust in Mars' polar caps are perhaps the most compelling climate records on the planet. Through a recent collaboration with Peter Huybers (Harvard), we discovered that the finest-scale beds in the polar layered deposits are often periodic, with a characteristic thickness of 1 to 2 meters. Graduate student Mike Sori, in collaboration with Huybers and Oded Aharonson (Caltech), is now exploring how different formation mechanisms might record changes in solar radiation due to long-term variations in Mars' orbit, and whether we can identify these changes by analyzing images of the polar stratigraphy.
(*) Ancient oceans and floods on Mars -- Several lines of evidence suggest that an ocean might once have filled the northern lowlands of Mars, but topographic profiles along the margins of the lowlands do not follow surfaces of equal gravitational potential (i.e., sea level), as the shorelines of a standing body of water should. In a recent collaboration with Jerry Mitrovica (Harvard), Michael Manga and Mark Richards (Berkeley), Isamu Matsuyama (U. Arizona), and Amy Daradich (U. Toronto), we showed that these long-wavelength topographic trends can be explained by deformation that occurred in response to true polar wander (TPW), a reorientation of the planet with respect to its rotation axis.
Mars has also experienced huge floods that may have been the largest ever to occur in the solar system, but poorly constrained flow depths and velocities make it difficult to estimate the discharge (flux) of these ancient flows. Graduate student Hendrik Lenferink is conducting laboratory experiments to constrain the discharge of the floods based on the paths they followed as they emptied into the northern lowlands.