Spatio-temporal variation of bright ephemeral features on Titan's north pole

Abstract

We identify and document the instances of bright ephemeral features (BEF) - bright areas that appear, disappear, and shift from flyby to flyby on Titan's north pole, using the Cassini Visual and Infrared Mapping Spectrometer data set, thereby developing a sense of their spatial distribution and temporal frequency. We find that BEFs have differing geographic location and spatial extents. However, they have similar observation geometries and orders of surface area coverage and are mostly accompanied by specular reflections. We find the BEFs to represent either broad specular reflection off of a recently wetted surface on the north pole of Titan or a near-surface fog - both owing to probable recent rainfalls. Our surface model constrains the surface roughness to be of 9°-15° indicating the approximate vertical relief of the region to be that of cobbles. We also find that within less than two Titan days the BEF (if on the surface) might infiltrate into the subsurface. We hypothesize the parts of BEFs that extend into the maria to be precipitation fog.