An animated Pluto fly-over

An animated Pluto fly-over

Spooky, and frickin' awesome!

I guess I never really thought about it before, but I was not expecting to see that Pluto has quite distinct light/shadow patterns. I didn't realize it would receive enough sunlight for that. Of course I knew that it has no internal source of light, and that therefore the sun must light it enough for strong earth telescopes to see it, but in the back of my mind I thought the overall ambience would be much darker.

I'm also really interested to hear the scientific theories explaining those areas with no craters or mountains. The mission spokesmen are calling them plains, but the illusion formed by the pictures is that the mountainous areas seem to end at a sea coast. If you think about it, most of our own planet has no craters or mountains when viewed from space, but that's because most of our planet is covered with liquid. Are there some types of oceans on Pluto? If so, what exactly do they consist of? If so, they can't be entirely frozen solid, because a frozen surface would show the effect of impacts, so they would likely have some kind of liquid aspect to fill in the impact craters. Despite the planet's cycle of day and night and the great difference in distance between its closest and farthest points from the sun, scientists believe that Pluto's surface temperature varies little - the difference between the high and the low is minimal, which means that a constant state of liquefying and refreezing is unlikely on the surface, although it's not totally impossible. Fluorine, for example, is solid at temperatures below -363 Fahrenheit, and liquid between -363 and -306. That is approximately the right range for a constant process of liquefaction and solidification in Pluto's temperature range. That's not a real explanation because no large concentrations of fluorine are evident, but the explanation could be something kind of like that.

More likely is that some warmer substance continuously bubbles up in liquid form from the interior of the planet and fills in the craters before it freezes at the surface temperatures, but our current understanding of thermodynamics suggests that Pluto should be too cold to be geologically active, unless it contains some kind of sub-surface ocean which somehow stores heat generated from some previous event, like a collision between Pluto and Charon in the distant past.

All of this is way beyond my level of scientific understanding, so I can't wait to see what the data shows and how the scientists interpret it.