[X] My Assistant

[Olvegg]

New article in New Scientist

[ngunn]

Just a thought: I have been thinking about the objection to the volcano hypothesis on the gounds that no temperature rise is observed at the bright spot. We normally think of erupted material being hotter than its surroundings but does this always have to be the case? When CO2 is released from a fire extinguisher the result is cooling. Could a Titan 'volcano' work like that? Could there in fact be different types of volcano on Titan (or different stages in the history of a volcano), some releasing heat while others cause refrigeration or are at least temperature neutral?

[Rob Pinnegar]

Momentarily going off the topic of New Scientist to answer this:

We normally think of erupted material being hotter than its surroundings but does this always have to be the case?

One would normally expect erupting material to have to start out as being warmer, or at least less dense, than its surroundings. However, I suppose it's technically possible that a subsurface reservoir of pressurized material, in thermal quasi-equilibrium with its surroundings, could "leak" gas that would cool off enough by adiabatic expansion to get below the ambient temperature.

The only thing is, how could this happen in nature? Where could that pressurized subsurface reservoir have come from, and how could it sustain itself over long periods of time? We'd need a workable scenario before proposing something like this.