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S. Ferraz-Mello, H. Hussmann (IAG-USP)
This communication aims at presenting some results on the joint evolution of the Saturnian satellites Titan and Hyperion. The motion of these satellites present a 4:3 period resonance and their study is made difficult by the high eccentricity of Hyperion (which oscillates between ~0.08 and ~0.13 with a 18.8 yr period). A chaotic region that, according with Bevilacqua et al. (1980), cannot be crossed in a slow and `smooth' evolution surrounds the domain where the system evolves. Bevilacqua et al. also suggested that Hyperion was formed via accumulation of planetesimals originally inside a stable island of libration while Titan was depleting, by collisions or ejections, the zones where the bodies could not escape the chaotic behavior. However, these assertions are only valid if Hyperion is kept in its current very eccentric orbit. If the eccentricity of Hyperion has been enhanced by the interplay of the 4:3 resonance with Titan and the tidal evolution of Titan's orbit, then, simulations show that a past smooth capture was possible. The main difficulty in a scenario where Hyperion was captured in a low-eccentricity resonant orbit is the slowness of Titan's evolution process. In this communication, several conditions are explored to assess the dissipation parameters of Saturn compatible with a capture less than 5 Gyr ago. Preliminary results indicate 1/Q ~3 x 10'5. This value is compatible with the value 1/Q = 1.5 x 10'5 established by Goldreich's (1965) from the proximity of Mimas to Saturn and consistent with a linear dependence between Q and the period of the tides. (The tides raised by Mimas on Saturn have a period almost twice of the period of the tides raised by Titan.)
Acknowledgements: FAPESP & CNPq (Brasil) and DFG (Germany).
The author(s) of this abstract have provided an email address for comments about the abstract: sylvio@astro.iag.usp.br
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.