Post-Cassini Exploration of Titan : Science Goals, Instrumentation and Mission Concepts

As Cassini arrives, we expect Titan to rise in prominence in solar system exploration to become second only to Mars, both as a planetary environment rich in geological, meteorological and oceanographic processes, as well as an astrobiological laboratory where the first steps in prebiotic chemical evolution may preserved by the profoundly low temperatures. Post-Cassini exploration of Titan may be expected to focus on surface and subsurface chemistry, together with the meteorological and geological context for these chemical deposits. One environment already identified to be of likely interest is the melt sheet and ejecta blanket associated with large impact craters, where melt (i.e. liquid water) may have interacted for thousands of years with the tholin deposits that rain down from the atmosphere. Amino acids, pyrimidines and other prebiotic molecules are produced and then frozen in place in such an environment, which cannot be adequately reproduced in the laboratory. Data from the Cassini RADAR and other instruments should be able to identify craters and melt sheets on Titan's surface. Concepts for advanced instrumentation to address these science goals are already under development, with particular attention to chromatography with chiral discrimination and accurate determination of enantiomeric excess in specific molecules. A promising platform is a dirigible airship with a surface-sampling capability. Such a mission launched for example in 2010 could loiter at high northern latitudes in the 2015-2020 timeframe to take advantage of near-continuous direct-to-Earth communication during polar summer.