NEW PHOTOS OF PLUTO

The New Horizons probe has been slow to send back its images of Pluto, but they're coming in now and they're exceeding expectations.

Here's (above) an Everest-type series of mountains next to what appears to be a lava lake or a glacier.

Here's (above) the remnant of a shield volcano. It's possible that the lava coming out of Pluto's mantle was liquid water. 

Here's (above) a field of craters, most of which are about a kilometer across. They're not impact craters, but are cheese-type holes only ten feet deep in a bed of solid nitrogen. 

 Above, the five moons of Pluto and their relative sizes.

Above, that's Charon, the biggest of Pluto's moons. It's half the size of Pluto which makes it the largest moon in the solar system relative to the size of its host planet. This is an astonishing photo because it reveals a world which is divided into two distinct parts separated by a belt of stress cracks.

Seeing this reminds me of the speculation that Earth once had two moons, one following behind the other in the same orbit. The smaller moon caught up with the larger one and slowly squashed into it with the result that today half of our moon has a substantially thicker crust than the other half.

I call this speculation because there's another scenario that might also explain the thinner crust on our side. Advocates say that early on, our moon was closer than it is now, and was heated by the newly formed molten Earth. The heat softened the moon's crust on our side allowing volcanoes to spew out lava that changed the surface of the side facing us. This explanation has less credibility for me because it would lead to a thickening on our side, not a thinning, which is what we see.

Anyway, the squashed appearance of Charon lends support to the idea that some sort of gradual collision happened there.

That's all I have to say about Pluto, but I can't resist putting up this photo of Phobos, a moon of Mars. Phobos is much closer to Mars than our moon is to us, and it appears to be spiralling in for a crash. The white smears on the right are thought to be stretch marks as the moon is being pulled apart by tidal forces.

My source for this photo didn't include an estimate for the time of impact, so maybe it's no time soon. When it occurs the debris is expected to form a ring around the planet.