Titan is the only planetary body other than Earth known to have an active hydrological cycle, with liquid methane rain, rivers, lakes, and seas. Also similar to Earth, Titan has an unusually small number of impact craters for its age and size compared with other moons of Saturn, which is attributed to erosion by its methane-based hydrological cycle. Impact craters can be useful because they expose the otherwise inaccessible subsurface of Titan, providing information about the interior composition and illustrating the evolution of cratered surfaces over time.
Anezina Solomonidou of the European Space Agency and collaborators investigated nine impact craters within the equatorial and mid-latitude regions of Titan using data from the Cassini spacecraft’s Visual and Infrared Mapping Spectrometer (VIMS) and Radio Detection and Ranging (RADAR) instruments as well as the Huygens probe. These data showed two distinct types of craters, those with an organic composition and those with a mixture of organic materials and water ice. The organic-rich impact craters were situated mainly within the equatorial dune fields, while those with detectable water ice were in the mid-latitude plains. This latitudinal dependence of crater-floor chemistry is likely related to the local weather, with the mid-latitudinal craters receiving more methane rain than the craters in the equatorial dune fields. This increased precipitation at the mid-latitudinal craters effectively cleans the craters of their sediments through erosion, while equatorial craters become covered in sediment over time. Furthermore, the dune-field craters also have a notable difference in composition between their crater floors and their surrounding ejecta, indicating that the surface environment does not affect the subsurface. This study highlights that Titan is a dynamic planetary body and reveals information about one of the dune-field impact craters, Selk, the planned landing site for NASA’s upcoming Dragonfly mission. READ MORE