Reconciling scales in global seismology

Titan, the largest moon of Saturn, is the only satellite of the Solar System with a substantial atmosphere, dominated by nitrogen and methane. With a surface temperature of 94 K and a surface pressure of 1.44 atm, methane is close to its triple point and is the major actor of Titan's active climatic cycle with methane evaporation, clouds and rain (analogous to Earth's water cycle). The landscapes of Titan were observed for nearly 13 years by the Cassini spacecraft and the Huygens probe. The wide variety of morphologies observed (dunes, mountains, seas, lakes, rivers...) testifies to the geological richness that Titan shares with the Earth. In this seminar, I will present our work combining radar and hyperspectral data provided by the Cassini-Huygens mission with models of valley and river network evolution to better understand the processes at work that sculpt these landscapes. We develop quantitative criteria to compare 3D morphologies obtained by numerical simulation with those derived by photogrammetry. These criteria are validated on Earth’s landscapes. We simulate morphologies similar to those observed and show that landscapes at the equator are mainly controlled by river incision and mass wasting such as landslides, and may be very young, less than a few millions years.