Winds and tides of Ligeia Mare, with application to the drift of the proposed time TiME (Titan Mare Explorer) capsule

We use two independent General Circulation Models (GCMs) to estimate surface winds at Titan's Ligeia Mare (78 degrees N, 250 degrees W), motivated by a proposed mission to land a floating capsule in this similar to 500 km hydrocarbon sea. The models agree on the overall magnitude (similar to 0.5-1 m/s) and seasonal variation (strongest in summer) of windspeeds, but details of seasonal and diurnal variation of windspeed and direction differ somewhat, with the role of surface exchanges being more significant than that of gravitational tides in the atmosphere. We also investigate the tidal dynamics in the sea using a numerical ocean dynamics model: assuming a rigid lithosphere, the tidal amplitude is up to similar to 0.8 m. Tidal currents are overall proportional to the reciprocal of depth-with an assumed central depth of 300 m, the characteristic tidal currents are similar to 1 cm/s, with notable motions being a slosh between Ligeia's eastern and western lobes, and a clockwise flow pattern. We find that a capsule will drift at approximately one tenth of the windspeed, unless measures are adopted to augment the drag areas above or below the waterline. Thus motion of a floating capsule is dominated by the wind, and is likely to be several km per Earth day, a rate that will be readily measured from Earth by radio navigation methods. In some instances, the wind vector rotates diurnally such that the drift trajectory is epicyclic. (C) 2011 Elsevier Ltd. All rights reserved.