Storms, Lakes & the Methane Cycle on Titan Lure us with Earth-like Qualities to an Exotic World

Titan’s surface appears familiar. We recognize the lakes that resemble those on Earth, along with channels indicative of rainfall. In addition we find washes like those in Arizona and dunes reminiscent of Namibia, Africa, which are shaped by weather. These terrestrial-like features result from Titan’s unique resemblance to Earth. In Titan’s atmosphere, the second most abundant gas in the atmosphere is methane, which, like water on Earth, exists as a gas, liquid and ice, and cycles between the atmosphere and surface. Similar to Earth’s hydrological cycle, Titan sports clouds, rain, and lakes. Yet, Titan’s cycle differs dramatically from its terrestrial counterpart, and reveals the workings of weather in an atmosphere that is ten times thicker than Earth’s atmosphere, that is two orders of magnitude less illuminated, and that involves a different condensable. Recently Titan has been explored in great detail with measurements conducted on Titan’s surface (by the Huygens Probe) and by ongoing remote observations from Cassini and ground-based telescopes. Now at the end of Cassini's Mission, we find that Titan's weather, climate and surface-to-atmosphere exchange of volatiles vastly differs from the manifestation of these processes on Earth, largely as a result of different basic characteristics of these planetary bodies. This talk compares Titan and Earth's lower atmospheres, with the aim to understand the processes that control weather on each planetary body. We will conclude by entertaining the puzzling question of how Titan acquired and retains the methane in its atmosphere, which underlies the similarities of Titan and Earth.