Summer On A Dwarf Planet
Everywhere we look, the Solar System is far more complex and exotic than we expected.
Take Pluto. Back when I started reading science fiction, and getting interested in astronomy, it was believed that Pluto was a lonely, deep-frozen ball of ice where nothing much happened. Now, we know that it orbits around a common centre shared with Charon, a body about half its size, while two small dark bodies, Hydra and Nix, orbit beyond the edge of a tenuous, dusty system of ring arcs - a compact toy of a system, as orderly and self-contained as an orrery. And we also know that Pluto has a thin atmosphere. It's been growing denser as the Pluto-Charon system swings through its closest approach to the Sun and surface ices warm and sublimate; and new results show that the atmosphere is warmer than expected because it contains about 0.5% methane, enough to cause a greenhouse effect (relatively warm, of course: it's still a chilly minus 180 degrees Centigrade). It's also warmer in the higher reaches of the atmosphere than near the surface, because sublimation of ices cools the surface while sunlight warms the resulting gases from the top down. When we get the same inversion effect here in London, smog is trapped under the warmer upper layer. Is there smog on Pluto, and if so, what is it made of? Still, pretty amazing that we can tell so much about a body so far away.
I was watching The Sky at Night yesterday, which had a nice bit on the Cassini orbiter's latest findings about Enceladus and Titan; there was also a piece on the various satellites currently orbiting the Moon, including the news ( to me) that the high-resolution camera aboard the Japanese SELENE (Kaguya) satellite had taken a picture of the Apollo 15 landing site. Turns out this happened last year, but I somehow missed it.
It's the pale blotch in the centre of the photo, visible because when the LEM return stage took off, its exhaust plume blew away dust on the surface, uncovering lighter material beneath. NASA is sending a new satellite, the Lunar Reconnaissance Orbiter, to the Moon later this year, with an even more powerful camera It's main mission os to study the poles, but it would very neat if it could take photographs of the Apollo 11 landing site, forty years on.