The Mountains of Titan

The surface of Saturn's largest moon Titan, as revealed by instruments on the Cassini spacecraft, has many Earth-like features, including mountains. These features have varying morphologies that are reflective of their origins and evolutions. These are described broadly as low rises, isolated blocks, mountain chains, integrated, rugged terrains, and flat, eroded mesas. The blocks, chains, and rugged terrains can have mountain heights up to 2 km and slopes up to 40 degrees. In polar regions, methane-ethane lakes inundate previously carved mountainous terrains, leading to drowned valley morphologies. Titan's mountains and crust are made of dominantly water ice. Since ice flows at shallower depths of burial than silicate rock, the apparent ~2 km limit to the mountain heights may result from this compositional restriction. However, the eroded appearance of the mountains reveals the strength of the erosional processes on Titan's surface, driven by atmospheric movement and enacted by methane rainfall. These processes may be acting even now to vigorously bring down the mountain elevations. Vast, rugged terrains, such as are found in the equatorial, leading hemisphere Xanadu region, may be ancient terrains that have undergone extensive tectonism and erosion. The mountains are found widely distributed around Titan, with a slight equatorial preference for mountain chains. All mountains, but especially mountain chains, since they record regional tectonic stress directions, will provide valuable limits on Titan's subsurface stresses and related crustal movement. Thanks to the Cassini Radar Team for their assistance in these interpretations.