Friday, November 30, 2012

Weird Worlds

The planet Mercury. At high noon, it's hot enough that lead would run like water. Just about the hottest place in the Solar System, excepting only the Sun itself. And just about the last place you'd go to look for ice cubes.

Except, of course, that you could keep a stash of them there. You'd just need to find the right place.

It's been a year for some really weird astronomy news. This week's highlight was confirmation of something long suspected. Like our own Moon, Mercury has polar craters that never, ever see sunlight. Even though the noontime sun is blisteringly hot, the eternal shadow of the polar craters gets cold, and stays cold. Vacuum is a very good thermal insulator. Radar data seemed to indicate it was a possibility, and that possibility was confirmed this week by the MESSENGER orbiter.

Not that this will ever have much practical use. Mercury is a horrible place to go for an ice run. In terms of energy, it's far easier to fling something into interstellar space than to put it into orbit around Mercury. But it illustrates nicely something Sir Arthur Clarke used to say: not only is the Universe stranger than we imagine, it's stranger than we can imagine.

Going a little farther afield, earlier in the year we had some interesting news from Mars. Last month, the rover Curiosity found some shiny things in the Martian soil. What kind of shiny things, you ask? Well, we don't know yet. Possibly a fairly mundane mineral, possibly something metallic. It will take some time to sift through the results. And even if there is gold in them thar hills, it'll be some time yet before we'll be able to go out and get it.

Mind you, people are working on ways to do just that. Take Elon Musk, for example. While his immediate goals are slightly more modest -- haul cargo to the Space Station, and later on, crew -- his ultimate goal is far more ambitious. What he really wants is to plant a colony on Mars. While it's an ambitious goal, and beyond our current abilities, it's something we'll eventually be able to do. Recent studies have revealed that Mars' atmosphere, while thin, is dense enough to provide enough protection from radiation that we could live on the surface. The radiation environment was really the last unknown. Everything else that a settlement needs is there: water, oxygen, carbon, metals. It'll be hard at first, but it's an important insurance policy for the species.

Going farther afield still, we can start looking at planets around other stars. It's hard to believe now, but only twenty years ago, we were still debating whether or not they were even possible. One of the projects I considered working on for my dissertation, way back when, was a numerical study on the theoretical stability of orbits in a binary star system. I had a gut feeling that if a planet were close enough to one or the other of the stars, the orbit would be stable enough that the companion star wouldn't perturb it and fling it off into deep space. As we've discovered time and again over the last twenty years, my hunch was right. And just last month, it was announced that we discovered a planet circling one of our nearest stellar neighbors, Alpha Centauri B. The planet, called Alpha Centauri Bb, is about our size. The similarities end there. Its year is just over three days long. It's 25 times closer to Alpha Centauri B than we are to our own Sun. While Earth pokes along at 30 kilometers per second, this planet screams across the sky almost five times faster. And, as you could imagine, it's hot. Noontime on Mercury is hot enough to melt lead. Noontime there is hot enough to melt steel. Needless to say, building a lander would be ... a challenge.

But a flyby would be relatively easy. Relatively, I say; it'd still be damn hard. We've given some thought to how to get the job done, though. The first serious proposal for an interstellar probe was the Daedalus project, a design study run by (who else?) the British Interplanetary Society. The idea is being updated and refined under Project Icarus, named for the son of Daedalus, and run by the BIS and the Tau Zero Foundation. They began the design study in 2009, and expect to be finished with that phase in 2014. Not that they expect to have a currently-realizable design by then. We've got a long way to go before we have that capability. But they expect to be able to figure out what we need to do to get there from here.

It's a marvelous time to be alive. I know people who'd rather live in the past. Not me. This is my time: here, at the beginning, with untold wonders spread out before us, waiting to be uncovered. There's no place I'd rather be.

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