Titan May Have Erupted Ice Recently

Large features on Titan resemble volcanic calderas.  The fact that no impact craters appear on the flows indicate that they are young.  But these are no ordinary volcanoes.  If the findings are confirmed, they erupted ice.
    Richard Kerr reported the scuttlebutt from last week’s Lunar and Planetary Science Conference in Texas.  Titan may have enough rock in its interior to produce heating by radioactive decay, “unlike Enceladus,” Kerr comments (a smaller Saturnian moon showing signs of recent resurfacing: see 03/04/2005 entry).  That internal heat could have melted the ice “tens or hundreds of kilometers down,” scientists think, and ammonia in the crust could lower the melting point of ice to allow slush to flow on the surface – but not forever, worries Caltech planetary physicist David Stevenson:

But Stevenson does wonder how Titan could still be flooding its surface with cryolavas this late in its life.  No impact craters have been seen on any cryovolcanic features, implying that they are relatively young.  Yet, notes Stevenson, billions of years of volcanic activity would have extracted the interior’s reservoir of ammonia.  Without that antifreeze, cryolavas could not flow. (Emphasis added in all quotes.)

The only way Stevenson could suggest a solution to this problem is if Titan is “somehow recycling its ammonia back into the interior.”

¹Richard A. Kerr, “Icy Volcanism Has Rejuvenated Titan,” Science, Vol 308, Issue 5719, 193 , 8 April 2005, [DOI: 10.1126/science.308.5719.193a].

This is just one of the conundrums about Titan if it is 4.5 billion years old as assumed by conventional wisdom.  The atmosphere is another problem.  It seems ad hoc to get the ammonia out to melt the ice, then plunge it back inside to reuse it later.  How many times could that cycle repeat?  Long enough to save face for scientists billions of years in the future when Titan was explored by humans?