The Lakes of Titan

The Cassini Radar flyby of Saturn's moon Titan on 22 July 2006 (T16) provides compelling evidence for the presence of liquid lakes on the surface of Titan. The radar images polewards of 70°N show over 75 circular to irregular radar dark patches from 3 km to over 170 km across, in a region where liquid methane and ethane are expected to be abundant and stable on the surface. Some patches are uniformly dark in appearance, with no measureable echo, while others vary in brightness. We interpret these as lakes based on their very low radar reflectivity and morphological similarities to lakes, including associated channels, location in topographic depressions and multiple shorelines. Lakes appear in a number of apparent states, including fully drained, partially dry and liquid-filled. These northern hemisphere lakes constitute the strongest evidence yet that a condensable-liquid hydrological cycle is active in Titan's surface and atmosphere, in which the lakes are filled through rainfall and/or intersection with the subsurface `liquid methane' table.