Enceladus is Hot

I spent Thursday afternoon in the lauded amphitheatre, with its comfortable chairs, tables and the ability to feed my (by then) hungry laptop. Today the amphitheatre was offering a double showing: 1.30 – 3.15, Enceladus. 3.30-5.15, Venus.

We were mere minutes late getting back from lunch, so the first session was in progress when I got there. The room was packed – there were no empty chairs, and people were piling up in the doorway. As the afternoon progressed, those in the doorway who had earlier been unable to snatch up the seat of someone leaving the room eventually started camping out on the floor and in the aisle. It took half an hour before I managed to snag a  seat, and another half an hour after that before I got a chair at a table with power.

The talks about Enceladus seemed mostly to be focussing on tidal heating. From what I understand, Enceladus is too hot. They’re working on theories to explain why its power output is so high (4-8GW, by one team’s measurement).

The main explanation, as argued by the groups presenting, seemed to be tidally-driven shear heating. This would generate 4-8 GW off of the South Pole  as a localized heat flux. This model implies that the eccentricity of the orbit is not constant. This power output is too much to be produced tidally if Enceladus is in a steady state.

At Enceladus’ present day eccentricity (if you ignore vapour transport, deposition, viscous dissipation and spatial variation), shear heating generates 4.8GW globally – which is important because power affects the decay rate of the eccentricity.

They explained all of this with a lot of math – equations and concepts I’ve never seen before, some of which I think they derived from basic tenets that I also don’t know.

One thing that was interesting to me, was this session the powerpoints had a whole lot more citations than those of any of the other sessions I’ve been to. The last 3-4 talks were clearly ordered intentionally. They all seemed to be building off of each other, citing papers with authors who were in groups to come. One author who seemed to be cited really, really frequently actually gave the last talk in the session.

Leave a Reply