<br>Jeff:<br><br>I would tend to agree with you that tidal heating often causes these types of geological stresses, but that does not seem to be the case here. <br><br><br>Alan Stern, New Horizons Principal Investigator: "One thing that we can say for sure is tidal energy isn't at work here. Pluto and Charon are in tidal equilibrium."<br><br>Alan Stern: "There is no giant body that can be deforming Pluto on an ongoing regular basis to heat the interior. So this is telling us you don't need tidal heating to power (the creation of these ice mountains). This is a really big discovery that we've just made."<br><br>John Spencer, New Horizons Mission Scientist: "This is the first time we have seen an icy world that isn't orbiting a giant planet. We see strange geological features on many of these moons and we usually interpret this as tidal heating. But that can't happen on Pluto. You do not need tidal heating to power ongoing recent geological activity on icy worlds. That's a really important discovery that we just made this morning."<br><br><br>Maria Zuber, a geophysicist at MIT: "Pluto has an active interior for reasons that are not at all clear. When ice-rich planetary bodies show evidence of resurfacing the interior it is usually tidal forces. But there is not a large nearby planetary body to raise tides. It's an extraordinary scientific mystery."<br><br><br><br><br><blockquote class="blockquote"><div class="italic"><i>Jeff Blazey said:</i><br><br>Pluto has a very large moon in a close orbit so there will be very respectable tidal forces exerted on both.<br><br>That will lead to all kinds of surface and sub-surface activity.<br><br>Uh, duh.<br><br>Jeff</div></blockquote>