[X] My Assistant

[Palomar]

Tiny Enceladus May Hold Ingredients of Life Yep, Titan's having to share the spotlight.

*A friend wrote the following to me privately yesterday, regarding Enceladus:

In the absence of a better idea from any quarter, I wondered about a large rocky meteor perhaps having impacted Enceladus at that anomalously warm point some time ago, burying itself in the moon's icy crust. The radioactive elements in the meteor, decaying over geological time periods like a lesser version of the ones powering volcanism in Earth's interior today, might be producing just enough heat to melt a deep portion of the crust, causing the outgassing, and elevating the surface temperature by the observed 20 deg.K.  That same relative warmth, softening the frozen crust, might quickly have erased the crater which resulted from the collision and removed the tell-tale evidence of the meteor's existence.
         
Being a comparatively rare event, an impact like this would explain why Enceladus alone has a hotspot while other icy moons of a similar size are uniformly cold and geologically dead, as we would expect.

It's an understatement to say that's an extremely interesting speculation.

-Cindy

[Guest_BruceMoomaw_*]

Yep -- the traces of radioisotopes (U, Th, K) in ordinary rock greatly heat the interior of a world ONLY because they're deeply buried, so that their extremely slowly-built up heat nevertheless escapes at an even more glacial pace. By contrast, even quite radioctive material near the surface wouldn't significantly raise the temperature of the nearby ice (or other substances) simply because its emitted heat energy could escape to the surface and radiate out into space before raising the surface material's temperature significantly.

I think we are definitely looking at localized tidal heating as the cause of Enceladus' hot spot -- unless we have some kind of very freakish (and unlikely) concentration of radioisotopes in one place in its rock core that's generated a slow convective flow of warm, relatively soft ice from deep inside Enceladus to the surface there.