FIRST USGS GEOLOGIC MAP OF SATURN’S MOON TITAN

Titan is the largest moon of the planet Saturn, with a mean radius of 2,575 km that makes it the second largest moon in the Solar System, second only to Jupiter’s Ganymede (2,634 km) and larger than the planet Mercury (2,440 km). Titan is also the only moon in the Solar System that has its own atmosphere, composed mostly of nitrogen and methane with a surface pressure of 1.47 bars. This atmosphere enables weather and climate, functioning similarly to Earth’s water cycle but with methane replacing water, and at much colder temperatures (~94 K or -180˚C). This results in an icy world with a geologically active surface, include winds producing seas of linear sand dunes, and hydrocarbon fluid producing rain, surface flows in rivers and streams, and accumulations in lakes and seas. Using images from NASA’s Cassini Saturn orbiter mission, we have produced the first global geologic map of Titan to be published by the U.S. Geological Survey (USGS). This global map, at the 1:20,000,000 scale, consists of 12 geologic units that characterize the geology of Titan as identified by Synthetic Aperture Radar (SAR) imaging at 2.2 cm at ~300 m to 1 km resolution and visible imaging at 938 nanometers at ~450 m/pixel. Unlike Jupiter’s volcanic moon Io or the tectonic- and/or impact-dominated icy moons Europa, Ganymede and Callisto, our mapping shows that Titan is a sedimentary world, dominated by gradational processes that erode, transport, and deposit icy and organic-derived sediments across the surface. From our mapping we recognize three broad divisions of Titan’s geologic history, from oldest to youngest: 1) formation and tectonic modification of icy mountain-hummocky terrains, and oldest, heavily-degraded impact craters; 2) formation and ongoing modification of extensive plains units containing relatively fresh to degraded craters; and 3) formation and modification of dune fields and filled and drained rivers, lakes and seas. Our map is currently in peer review at the USGS.