HR: 1035h
AN: P12B-02    [Abstracts]
TI: Coorbital Collision as the Source of Enceladus Heat
AU: * Peale, S J
EM: peale@physics.ucsb.edu
AF: UCSB, Dept. of Physics, Santa Barbara, CA 93106, United States
AU: Greenberg, R
EM: greenberg@lpl.arizona.edu
AF: U. of Arizona, Lunar and Planetary Lab, Tucson, AZ 85721, United States
AB: The source of energy for the observed plumes on Enceladus is a mystery. An explanation using tidal heating has difficulty in explaining the extreme localization of the plumes. That issue aside, the tides cannot produce enough dissipation to either account for the current energy loss or to store sufficient energy for later release, even given the current or likely past orbital resonances (Meyer and Wisdom, 2007). Here we consider the possibility that Enceladus has absorbed its coorbital in a collision gentle enough to preserve ancient cratering records, but with sufficient energy deposition to power the plumes for at least a short time. Numerical integration of Enceladus, its coorbital, Dione, and Titan, with Dione and Enceladus on converging orbits due to differential tidal expansion, leads to capture of Enceladus into the 2:1 orbital resonance, while destabilizing the coorbital into a collision with Enceladus. The relative velocity of the collision is only slightly above the escape velocity from Enceladus of 0.24 km/sec. One calculated collision had a relative velocity at impact of 0.26 km/sec with relative kinetic energy of 3.8× 10²⁹ ergs for m=0.01m_E. If most of this is deposited into Enceladus, it would power the energy lost in the plumes of 6 GW (Spencer et al. 2006) for about 200,000 years. The collision has the virtue of depositing the energy rather locally, and an underdense warm region after the satellite has equilibrated would naturally migrate to the pole to restore rotation about the axis of maximum moment of inertia.
DE: 5418 Heat flow
DE: 5420 Impact phenomena, cratering (6022, 8136)
DE: 5450 Orbital and rotational dynamics (1221)
DE: 5462 Polar regions
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting