Astronomy and Astrophysics – Astronomy
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dda....41.0809z&link_type=abstract
American Astronomical Society, DDA meeting #41, #8.09; Bulletin of the American Astronomical Society, Vol. 41, p.934
Astronomy and Astrophysics
Astronomy
Scientific paper
The giant crater Odysseus (400km in diameter) formed after a massive impact on Saturn's moon, Tethys. The same impact event may help explain a transient high heat flux during the early history of the satellite implied by Ithaca Chasma. The inferred heat output based on the flexural uplift of the canyon is far greater than what radioactive decay may provide [Giese et al. 2007, Geophys. Res. Lett. 34, L21203]. The most likely alternative is an episode of tidal heating, which requires the satellite's orbital eccentricity to be in the range 0.001-0.02 [Chen and Nimmo 2008, Geophys. Res. Lett. 35, L19203]. The eccentricity damping timescale resulting from tidal interaction, however, was so short that the inferred eccentricity could not be primordial. Thus an eccentricity excitation mechanism is necessary. We found that a possible scenario is a mean-motion resonance with Dione followed by a giant impact on Tethys which broke the resonance and formed Odysseus.
Our numerical study indicates that trapping into the 3:2 mean-motion resonance between Tethys and Dione allows Tethys' orbital eccentricity to grow to about 0.003. Although less likely, higher eccentricity may be achieved if the satellites can avoid the e-Dione resonance and enter the e-Tethys one. This may marginally generate the inferred heat flux. The two satellites must have escaped the resonance since they are not in resonance today. One possible event leading to the escape is the giant impact that formed Odysseus. Our calculation shows that an icy projectile with a diameter of 60-70 km and an impact velocity of 5-7 km/s can both break the Tethys-Dione resonance and form a crater on Tethys near the size of Odysseus.
Nimmo Francis
Zhang Ke
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