I have to leave, but want this here to get a reply if you have time today. I'll try to answer more replies Sunday and apologize in advance if I don't get back to you quickly. Mimas is the smallest body in the solar system know to be in hydrostatic equilibrium. Mimas is 200 miles in diameter. Pluto is nearly five times larger. Pluto's density does not suggest that it is porous like a comet or asteroid. Ceres is the closest analog I was expecting and Pluto is over two times as wide. Something is reforming the surface of Pluto! This is something that I was not anticipating at all, and it brings up a multitude of possibilities. Here is hoping that the next two years will answer some questions.Remember how the other comets are misshapen and porous? Well, Pluto is big enough to pull itself back into a spherical shape (hydrostatic equilibrium). Its gravity is strong enough to pull the rocks back down and close up these porous "gaps" left by the escaping volatiles.