New Insights From A Survey Of Mountainous Terrain On Titan Using The Cassini RADAR Altimeter

Despite the fact that the Cassini mission ended in 2017, advanced processing techniques enable new information to be gained from existing datasets. The recent development of delay-doppler processing for the altimetric data collected by Cassini's RADAR instrument allows us to investigate the topography of Titan at higher spatial resolution than previously possible. By combining this new topography data with existing SAR imagery, it is possible to gain new insights into the nature and evolution of Titan's many surface features. Mountainous and hummocky terrains are an intriguing target for this analysis, given their relatively dramatic topography and likely connection to active surface processes. Using the newly produced delay-doppler data set, we have conducted a survey of elevated terrain on Titan and discovered that previous terrain classifications may need to be revisited. Units previously classified as either "mountains" or "hummocks" share a similar signature in the altimetry data, characterized by a diffuse region of reflected power above a higher intensity base reflection, which is typically level with the surrounding plains. If we assumed mountainous regions were uniformly higher elevation than the surrounding plains, we would not expect to see such a base reflection. The presence of this plains-level base reflection instead indicates that mountainous terrains on Titan may be heavily eroded, down to the basin level in many areas. In order to explore this hypothesis, we compare models of radar altimetry and SAR images over synthetic surfaces to observed delay-doppler and SAR radargrams.

In addition to these mountainous terrains, we also describe a number of other topographic features found within the delay-doppler dataset. These include a mountainous area in the north polar region that does not exhibit the typical altimetric signature described above, the raised rims found within the lake district, and a dome-like feature resembling the potentially cryovolcanic "hot crossed bun" formation.