Could Charon, Pluto’s largest moon, have watery volcanos spewing forth as we speak? According to maths, yes, but according to other’s views of geology, no.

Steven Desch at Arizona State University, Tempe, suggests that crystalline water seen at Charon is evidence of cryovolcanism, and he did some mathematical modelling to work out how Charon and other large Kuiper Belt Objects (KBOs), often considered to be geologically dead, could be storing liquid water or ammonia that is able to erupt through the crust even today.

Desch claims that energy is stored at the core of the KBOs and released at a different rate than predicted, and manages to keep the tempeture just right to maintain liquid ammonia temperatures under the crust – even today. This is the hard part, he says. Getting that liquid to the surface isn’t as difficult.

Desch’s model suggested a cut off radius of 500km for KBOs that could support cryovolcanism, any smaller than that and the model didn’t hold. Corroborating his model, he says is the presence of ammonia hydrates on Charon, “They provide a nice antifreeze,” Desch says.

But all is not as it seems. Bill McKinnon, from Washington University in St Louis, told me that as far as he’s concerned, Desch’s model is “geologically impossible”. He doesn’t see how the magma could be hot enough to break throuh the surface of Charon. What is more intriguing to him is the presence of ammonia ice on the surface. “You don’t’ need vulcanism to explain crystalline ice,” McKinnon says, “we see it everywhere”.

Mike Brown, at Caltech (not tempted to attend the Texan gathering), is expert in all things Kuiper (and author of a paper on related Kuiper belt objects that come from the same massive collison – published in Nature yesterday), especially crystalline water. He remains to be convinced. “Cryovolcanism is cool (literally) so everyone wants to jump to that answer, but the real answer is probably much more dull,” he told me. Just because crystalline water ice is everywhere doesn’t mean, of course, that cryvolcanism is nowhere, Brown says, but to him it’s clear that the crystalline water ice is not nearly enough evidence to prove the volcano hypothesis.

I didn’t manage to get hold of Desch in person to ask him – so if I learn the real answer I’ll update here…

Oh, and if you didn’t know, Charon in Greek mythology was the Ferryman of the dead. Lovely.

Could Charon, Pluto’s largest moon, have watery volcanos spewing forth as we speak? According to maths, yes, but according to other’s views of geology, no.

(more…)