Observing Titan's Polar Wetlands
The hydrological cycle on Titan is particularly interesting because there are few places in the solar system where liquids exist on the surface of a solid body for a significant amount of time. Understanding the transport of methane through the regolith and atmosphere may ultimately constrain the source(s) of methane, which will help to explain the evolution of the atmosphere. If we assume that clement conditions on terrestrial exoplanets are similar to those on Earth, and that the condensable substance on the surface is also abundant in the atmosphere (e.g., as clouds, ice, and rain), then we may encounter similar challenges during the remote characterization habitable terrestrial exoplanets as we do when studying Titan’s hydrology. However, there won’t be spacecraft missions with probes to validate the interpretation of exoplanet spectra in the foreseeable future, so we’ll have to make the best use of the remote observing techniques that have been developed for studying our solar system. I’ll present ground-based, high-resolution, near-IR observations of Titan, which constrain the abundance of methane, while describing the pitfalls and successes of measuring the relative humidity at the surface. A comparison of the retrievals with the surface humidities predicted by circulation models that include parameterized surface hydrology suggests that we can place interesting constraints on the source region for methane. I’ll present a spectroscopic search for the isotopic signature of condensation, which would provide a vapor-phase diagnostic of deep, precipitating convection, and describe the requirements for such observations based on a predictions from a Rayleigh distillation model.