Tidal heating of Ariel

Abstract

Ariel and Titania may have passed through a 4 : 1 mean-motion commensurability 3.8 billion or more years ago. Temporary capture into the e A 3 resonance associated with this commensurability causes large increases in the orbital eccentricity of Ariel. The satellites ultimately escape from the resonance via capture into secondary resonances, which drag the system into a chaotic zone. During evolution through the 4 : 1 commensurability, tidal heating could have increased the inyernal temperature of Ariel by up to about 20 K. At the time the resonance was encountered, early in the history of the Uranian system, the internal temperature of Ariel would probably have been relatively high due to radiogenic and accretional heating. The additional increase in temperature caused by tidal heating during passage through the 4 : 1 commensurability may have triggered the geological activity that led to the late resurfacing of Ariel. Ariel may have encountered many other high-order resonances with the other Uranian satellites, however, the probability that any of these significantly affected its evolution is small.