From the Executive Summary:
Titan, a complex, Earthlike system abundant with organics, should be the next scientific target in the outer Solar System. Titan shares features with both icy satellites and the terrestrial planets. It is subjected to tidal stresses, and its surface has been modified tectonically to form mountains and likely also by cryovolcanism, where liquid water and methane make their way to the surface from the interior. Titan has the largest concentration of organic material in the Solar System aside from Earth, and its active hydrological cycle is analogous to that of Earth, with methane replacing water. Titan's clouds, rain, flash floods, and greenhouse and anti-greenhouse effects may provide important lessons for Earth. Albeit with bizarrely different chemistry, Titan's landscape is remarkably Earthlike, featuring dunes, streambeds, and mountain ridges, as well as polar lakes filled with liquid hydrocarbons. The thick, largely nitrogen, Titanian atmosphere varies seasonally in temperature, dynamical behavior, and composition, including a winter polar structure analogous to Earth's ozone hole, and a mission launched in the 2015-2022 time-frame has a prime opportunity to measure a season complementary to that observed by Cassini. Although Titan is similar to Earth in many ways, its atmosphere is unique in the solar system in experiencing strong dynamical forcing by gravitational tides (a trait Titan may share with many extrasolar planets). Study of these scientific aspects maps well to NASA's scientific objectives as presented in the first Decadal Survey report, the 2006 Solar System Exploration Roadmap, the 2007 NASA Science Plan, and the 2006 Outer Planets Assessment Group Pathways Document. Titan, with low gravity and a thick atmosphere, is also uniquely accessible for in situ exploration, allowing a broader range of scientific tools to be affordably brought to bear on its exploration than other satellites. Therefore, Titan, a rich, diverse body offering extraordinary scientific return,
is an excellent choice for the next Flagship mission.
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