Post by Jeremy Brossier, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Planetary Research, Berlin, Germany.

During the last thirteen years (2004 – 2017), the Cassini-Huygens mission allowed a real revolution in the exploration of Titan, the largest moon of Saturn. This mission has revealed that Titan is – in many aspects – very similar to Earth. Titan is a frozen version of Earth, where methane behaves as water, and water ice may be as hard as rock. Despite its strange characteristics, Titan undergoes a rich variety of surface processes that are likewise analogous to those on our planet. Titan being entirely shrouded by a dense atmosphere made of dinitrogen, methane and solid organic particles (i.e. tholins), direct observation of its surface is only possible through radar data, as well as infrared data within specific wavelengths intervals. SAR images from the radar, allowed identifying various landscapes on the moon (see Image 1), and evaluating their global distribution, notably for the lakes and dunes. Lakes are mostly confined around the poles, while the dunes dominate the equatorial belt. Thus, the shape of Titan’s surface seems quite well understood thank to SAR images, however, it is crucial to determine not only the morphology, but also the nature of the material composing or coating the various landscapes to better understand the geology of this intriguing moon.

Image 1: A few examples of Titan’s landscapes seen through SAR images, including (A) mountain chains embayed by plains, (B) undifferentiated plains, (C) impact crater, (D) dunes, (E) river channels, (F) small lakes, and (G) a close up of the second largest sea, namely Ligeia Mare. SAR images were acquired during Titan flybys (A, B) T43 in May 2008, (C) T77 in June 2011, (D) T21 in Dec. 2006, (E) T44 in May 2008, (F) T19 in Oct. 2006, and finally (G) T28 in April 2007. Note that Titan flybys are tagged with the abbreviated target name “T” and the flyby number.

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