What a week!
The tenth planet of the solar system has been discovered, with the provisional name 2003 UB313 and a more elegant name to be unveiled at some point. It's been 75 years since the solar system added a planet to the family, and this may well not be the last. And no, I don't believe for a second that Pluto will ever be demoted -- it's a planet, with far more reasonable arguments for its status than, say, Europe's as a continent, and ever more shall be so. Brian Marsden tried that trial balloon of demoting Pluto a few years ago, and the backlash was clear. Once a planet, always a planet, I think is the way it's going to be, and I'm entirely comfortable with that.
One proposal that makes sense to me is that we set an arbitrary cutoff at 1,000 km radius. Nice round number. Pluto and the new planet qualify, nothing else yet discovered does. If we find more of these big objects, so be it, then the solar system grows.
And that's not the only big new object of the week. Another newfound Kuiper Belt Object, also bigger than any other found before, but less than Pluto, and this one has a moon as well, allowing its mass to be nailed: 1/4 Pluto's.
And there's a lovely new lake on Mars, from Mars Express, frozen (all the way down??) in the bottom of a crater, but shining blue and looking ready to dive into. The first naked ice on Mars, at least outside the polar caps.
And Enceladus, Saturn's tiny moon that Cassini just swept by twice as close as the space station's orbit above Earth. An extraordinarily active world, for its tiny size, emanating gases through tectonic cracks.
Wow. And all this as the shuttle's dramatic roller coaster unfolds, already quadrupling the Internet record set by NASA's website just three weeks ago with the Deep Impact mission. Quite a week in space news.