Mercury's capture into the 3-2 spin-orbit resonance including the effect of core-mantle friction - Astrophysics > Earth and Planetary AstrophysicsReportar como inadecuado




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Abstract: The rotation of Mercury is presently captured in a 3-2 spin-orbit resonancewith the orbital mean motion. The capture mechanism is well understood as theresult of tidal interactions with the Sun combined with planetaryperturbations. However, it is now almost certain that Mercury has a liquidcore, which should induce a contribution of viscous friction at the core-mantleboundary to the spin evolution. This last effect greatly increases the chancesof capture in all spin-orbit resonances, being 100% for the 2-1 resonance, andthus preventing the planet from evolving to the presently observedconfiguration. Here we show that for a given resonance, as the chaoticevolution of Mercury-s orbit can drive its eccentricity to very low valuesduring the planet-s history, any previous capture can be destabilized wheneverthe eccentricity becomes lower than a critical value. In our numericalintegrations of 1000 orbits of Mercury over 4 Gyr, the spin ends 99.8% of thetime captured in a spin-orbit resonance, in particular in one of the followingthree configurations: 5-2 22%, 2-1 32% and 3-2 26%. Although the present3-2 spin-orbit resonance is not the most probable outcome, we also show thatthe capture probability in this resonance can be increased up to 55% or 73%, ifthe eccentricity of Mercury in the past has descended below the critical values0.025 or 0.005, respectively.



Autor: Alexandre C.M. Correia, Jacques Laskar

Fuente: https://arxiv.org/







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