Geometry and spatial distribution of lenticulae on Europa

Abstract:

Title: Geometry and spatial distribution of lenticulae on Europa

Order of Authors: Cansu Culha (Stanford University); Michael Manga (University of California, Berkeley)

The surface of Europa contains several types of elliptical features, collectively called lenticulae. These features may have positive relief (domes) or negative relief (pits), may disrupt the crust (chaos), or discolor the surface (spots); some lenticulae have attributes of both domes and chaos (dome/chaos). We map the location, dimensions and shapes of all these features and their interactions with other surface features. We find (1) pits and domes have similar sizes; (2) pits are clustered in certain regions of the surface whereas domes, dome/chaos, and chaos terrains are more uniformly distributed; (3) chaos are larger than the other lenticulae; (4) lineaments do not divert their paths around lenticulae. Taken together, these observations are consistent with conceptual models in which lenticulae are created by convection or intrusion of liquid water bodies within the ice shell. Additionally, the observations are consistent with the notion that each type of lenticulae is a surface expression of dynamics within the ice shell at a different stage of the lenticulae evolution. The similar size and shape of pits and domes suggests that one may evolve into the other. Because domes are more numerous and more uniformly distributed than pits, they are more likely to represent the end stage of this evolution assuming the end-stage leaves a longer-lasting surface expression. We find no examples of lineaments crossing pits but lineaments do cross some chaos, implying that pits are younger than chaos and consistent with pits being the earliest stage in the evolution of lenticulae. Models also predict that larger features are more likely to disrupt the crust, which is consistent with dome/chaos and chaos being larger than pits and domes. The absence of lineaments deflected by lenticulae implies either that the stresses created by lenticulae are too small to influence lineaments, or that the complete evolution of lenticulae occurs on a time scale that is short compared to the time between the formation of lineaments at a given location.