Planetary Science Seminar spring-2018

Sean Faulk: Surface-atmosphere connections on Titan Titan harbors a rich hydroclimate with geomorphological evidence of surface runoff, subsurface reservoirs, and sediment transport by intense rainstorms. Regional patterns in these surface features suggest corresponding regional climatic influences, namely in the form of precipitation from the atmosphere. A model coupling the atmosphere to a surface hydrology scheme is therefore required to fully explore Titan’s surface-atmosphere connections. Previous general circulation models (GCMs) of Titan have successfully reproduced Titan’s climate but have neglected basic representations of surface hydrology. I will present a new Titan GCM that includes simple parameterizations of surface and subsurface flow, infiltration, and groundwater evaporation, and discuss the resulting large-scale climate dynamics. The model promotes poleward methane transport by surface/subsurface flows into saturated high-latitude lowlands and equatorward methane transport by the atmosphere into unsaturated low-latitude highlands. Infiltration into unsaturated soils then dries the lower latitudes. The model therefore reproduces Titan’s observed equatorial desert and polar wetlands regions but within a more physically consistent framework than past GCMs. Kynan Hughson: Will it bend? Probing the mechanical properties of the shallow subsurface of Ceres from fractured terrains in its Nar Sulcus region. Nar Sulcus is a unique geomorphic terrain located in the southwest quadrant of Yalode crater on Ceres’ southern hemisphere. Geological mapping of the fractured terrain revealed that it contains two sets of mutually perpendicular fractures that we interpret to be low angle normal faults. We test the hypothesis that the topography and morphology of the Nar Sulcus normal faults are controlled primarily by a thin ice-rich elastic layer. We do this by mapping the structures in Nar Sulcus from Dawn spacecraft images, comparing their profiles to a single layer flexural-cantilever model for normal faulting similar to the one developed by Kusznir et al. (1991), and analyzing their displacement:length ratios using a method similar to the technique described in Cowie and Scholz (1992). This analysis, which is similar to the one conducted on the europan ice shell by Nimmo and Schenk (2006), estimates the elastic thickness and remote stress acting on the faults at Nar Sulcus.