TITAN'S EVAPORITES: INVESTIGATING SURFACE-ATMOSPHERE INTERACTIONS IN TIME

Cassini, a spacecraft in orbit around Saturn since 2004, has revealed Saturn’s largest moon, Titan, to be a dynamic world. With surface temperatures and pressures near the triple point of methane, the hydrocarbon undergoes a “hydrological cycle” much like water does on Earth. Unlike Earth, however, Titan’s surface liquids are not ubiquitous-- they seem to be located almost exclusively at the north pole. And yet, Cassini has observed a handful of surface wetting events after rainfall in Titan’s equatorial region as well as evaporite deposits in supposed “desert” regions. So the question remains-- why are the lakes and seas almost exclusively at the north pole? If liquid has been elsewhere on the surface, how long ago did it dry out? What factors control which lakes dry out first?

Global circulation models have begun to explore these questions from the dynamics perspective. Our study of Titan’s evaporites informs such models by providing the observational evidence of what Titan’s surface looked like in the past, both where the liquid has been and, potentially, if there have been compositional differences/similarities between different bodies. We conduct our analyses with data from Cassini’s Visible and Infrared Mapping Spectrometer, the only instrument able to distinguish the evaporites on Titan’s surface. A better understanding of the long-term climate is crucial for understanding Titan’s evolution over geological timescales-- the current estimates for the composition of the atmosphere can’t reconcile the rate of loss of methane in the upper atmosphere with that estimated in the volume of surface liquid.

As Titan is the only other body in the solar system with active hydrology, it offers a unique opportunity to investigate processes very similar to those on Earth operating on different variables. Understanding the dynamic processes on the Saturnian moon thus provides important context for studies of our own planet’s surface-atmosphere interactions.