Tidal Dissipation in Io and Enceladus

Dave Stevenson

November 23, 2009

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Abstract: Following a general introduction on tides and how they are dissipated, both in solid and in fluid bodies, I will focus on bodies where the tides dominate the energy budget and global behavior : I o and Enceladus. In both cases we have very recent relevant data, and we know that the heat released is excessive for steady state orbital evolution (the ultimate source of the energy). I will argue that the most likely resolution of this puzzle lies in both cases with the episodic (perhaps quasi-periodic) nature of the tidal heating mechanism over time scales of order millions of years. I will discuss the (largely unresolved) question of the physical origin of this cycle, focusing mainly on the idea that it is a stress build-up/failure/lubrication and volcanism/stress ramp down and annealing cycle for both bodies. I will also discuss whether this had relevance for other bodies (Europa, Moon, etc.)