Coupled Thermal Evolution and Tidal Deformation of Venus

The measurements of tidal deformation provide an important constraint on the interior structure of celestial bodies. In particular, the tidal Love numbers (k2, h2, l2) and the tidal lagging are sensitive to a moon’s or planet’s elastic and rheological parameters, density and temperature profiles of the mantle, and the state of the core. Constraining the current parameters of the body may also help us to gain an insight to its thermal history. In this context, a coupled approach based on the thermal and tidal modeling presents an additional source of information for the inference of interior properties. Here, we focus on the thermal history and the currently measurable tidal deformation of Venus. Despite its similarity to Earth in terms of size and mineralogical composition, Venus has apparently undergone a substantially different thermal evolution, the reasons of which are still to be fully understood. To calculate the thermal evolution, we utilise a 1d parameterised model of stagnant-lid convection (as described by [1]), including the treatment of heat-pipe magmatism, crust formation, and inner core growth. The set of thermally-evolved models with different initial properties is then used to calculate the tidal Love number k2 and the tidal quality factor Q, adopting an approach similar to [2]. For the tidal model, we first calculate the radial profile of Venus’s elastic parameters, corresponding to phase diagrams generated by the thermodynamic software Perple_X [3]. The tidal deformation is then computed using a layered model based on the normal mode theory [e.g., 4], with the rheological behaviour of the mantle described by the Andrade rheology [5]. We will use the coupled tidal-thermal evolution models to make predictions about the evolution and present day state of the interior of Venus. These predictions can be tested with future measurements of the recently selected VERITAS and EnVision missions. [1] Morschhauser, Grott, & Breuer (2011), Icarus, 212(2):541-558, doi:10.1016/j.icarus.2010.12.028. [2] Breuer et al., this meeting. [3] Connolly (2009), G3, 10:Q10014, doi:10.1029/2009GC002540. [4] Sabadini & Vermeersen (2004), ISBN 1-4020-2135-6. [5] Castillo-Rogez, Efroimsky, & Lainey (2011), JGR Planets, 116(E9):E09008, doi: 10.1029/2010JE003664