TITAN'S MENRVA CRATER AS A MASSIVE ANCIENT EXHUMED CRATER

Menrva crater is Titan’s largest confirmed impact feature. At 392 km width, modelling suggests the impact was large enough to fully breach Titan’s crust and splash subsurface ocean water up onto the surface. Previous mapping has shown that this crater had a complex erosional history, with fluvial erosion and organic dune deposition occurring interior to the crater.

Our re-analysis and mapping of the geomorphology of Menrva suggests that this impact scar is likely a massive exhumed structure and that the impact may have occurred early in Titan’s history. Evidence for this is from analysis of the fluvial networks. To the E of the crater, the Elivagar Flumina network starts near the eastern rim and widens as it flows across the apron away from the crater, in harmony with a topographic gradient decreasing elevation away from the crater. However, to the W of the crater an extensive channel network integrates from the distal ejecta region across the rim and into the crater. A nearby topographic trace suggests the topographic gradient to the west decreases elevation away from the crater – opposite to the observed channel network. Detailed examination also shows that the W channel incises a meander pattern across the western crater rim. The meander is consistent with gentle topographic gradient during channel formation, in contrast to the current rugged terrain around the crater rim.

A history that is consistent with all these observations is that an initial massive impact, followed by later extensive burial by thick organic deposits, resulted in a deep organic plain with an overall gradient from the W to the E. Later fluvial erosion created a large meandering channel network integrating from W to E. At some point, the sediment budget shifted and the organic landscape deflated as organic materials were removed, possibly from eolian activity. As the landscape lowered, the W channel cut down and across the crater rim, delivering fluvially transported materials into the crater. A sand streak trailing E from the Menrva crater which perturbs the Elivagar Flumina network is also consistent with this interpretation.

These observations suggest that Menrva is an ancient crater that has undergone burial, and exhumation of organic material. This interpreted deep history is testament to the complexity of Titan’s organic landscape evolution.