Coyette, Alexis ; Baland, Rose-Marie ; Van Hoolst, Tim

Poster presented at EGU General Assembly, EGU2019, 7-19 April, 2019 in Vienna, Austria on 2019-04-11

Abstract: The determination of rotation variations of Titan is based on measurements of the shift in orientation ofCassini RADAR images taken different flybys. Between 2004 and 2009, these images have shown that Titanwas rotating slower than expected for a satellite in synchronous rotation (non-synchronous rotation (NSR) of-0.024±0.018◦/year, Meriggiola et al., 2016).We here model the rotation of Titan from the angular momentum equations (or Liouville equations) of thedifferent interior layers of Titan. Our model includes the effect of tidal deformations of the different layers, of thedeviation from the hydrostatic equilibrium, of the dense atmosphere of Titan and of the flow in the subsurfaceocean on the rotation of Titan.Our results (published in Coyette et al., 2018) show that length-of-day variations with a period of a fewyears and due to angular momentum exchanges between Titan and its atmosphere can be large enough to explainthe observed deviation from synchronous rotation. This observed NSR could therefore be interpreted as anobservation of the length-of-day variations of Titan in that period of time. If our interpretation is correct, weexpect a rotation faster than the synchronous rotation rate between 2009 and 2014, period of time that has notbeen studied yet.

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Funding: ESA/PRODEX/PlanetInt