Exploring an Alien Meteorological Cycle
Emily L. Schaller, University of Arizona

Saturn's moon Titan is the only moon in the Solar System with a substantial atmosphere. Titan is also the only known body other than the Earth with an active meteorological cycle including clouds, rain, lakes, and rivers. Though Titan is similar to Earth in many ways, its distance from the sun makes it a frigid world with a surface temperature of only 95 Kelvin. The substance that forms clouds and rains down on the surface of Titan is not water but liquid methane.
Titan provides us with a unique laboratory in which to study a hydrological cycle on a planet other than Earth with a different condensable species.

The majority of methane clouds, lakes and fluvial features on Titan have been observed in the moist high latitudes, while the tropics have been nearly devoid of clouds and show an abundance of wind-carved surface features like dunes. Using the NASA Infrared Telescope Facility (IRTF), I have observed Titan on a near-nightly basis for over four years in order to understand its weather patterns.
Recently, an unexpected large outburst of cloud activity occurred in Titan's tropical latitudes that may have been associated with a significant amount of methane rainout. These observations may explain the presence of small-scale channels and dry riverbeds seen near the equator by the Huygens probe on its descent through Titan's atmosphere in 2005. Understanding Titan's methane-based hydrological cycle is vital for interpreting the variety and distribution of fluvial surface features seen by the Cassini Spacecraft.

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