January 18, 2006

Beeline to Pluto

As we speak, the New Horizons spacecraft is sitting on the launchpad in Florida, waiting for the conditions to be just right for launch. Yesterday the winds in Florida were too high, and today the mission control center in Maryland lost power, so the launch has been delayed twice. They’re scheduled to try again tomorrow afternoon, and with any luck this spacecraft will get off the ground and be on its way within 24 hours.

New Horizons is the long-awaited, long-delayed mission to study the outer planet Pluto. Pluto is the only one of the nine planets that hasn’t yet been visited by a robotic emissary from Earth, and the only reason a mission like this hasn’t been launched sooner is because of budget issues. But finally everything got approved and a space probe is going to be on its way, and not a moment too soon. Pluto’s orbit is elliptical enough that its distance from the Sun varies drastically over time. This gives the planet a definite “summer” and “winter”, where the atmosphere grows and shrinks depending on how warm the surface of the planet is. The thing is, Pluto is now getting further away from the Sun, which means winter is coming on, and its atmosphere is shrinking. So every year that goes by, the planet gets a little less interesting scientifically.

In fact, it’s just a lucky break that Pluto is considered a planet at all. In 1930, when it was discovered, astronomers had been long searching for a ninth planet. So when this little speck of light was found, orbiting out beyond Neptune, it immediately was classified a planet, even though they had no way of telling what it really looked like or how big it was. If it was big enough to show up in a telescope, it must be a planet, right? Well, over the decades we’ve found out that Pluto is tinier than they thought, smaller than any of the other planets, smaller even than the Moon. And it’s most likely not even a solid chunk of rock; instead it’s probably more like a comet, made up mostly of ice and dust, and maybe with a rocky core in the middle of it. In fact, pretty much everybody agrees that if Pluto had been discovered more recently, it wouldn’t have been labeled a planet at all.

Even more damaging to Pluto’s reputation is the discovery of thousands more objects out there just like it. Together, they make up what’s known as the Kuiper Belt, which is a lot like the asteroid belt only it surrounds the outer edge of the solar system. In the last ten years, with telescope technology advancing rapidly, a veritable cloud of icy rocks has been found orbiting just beyond Neptune. Many of them have moons of their own, and at least one of them, scientists figure, is bigger than Pluto itself. But there’s no chance that any of these objects are going to be classified as planets. They’re too small, they’re too irregular, and their orbits are too erratic. At best they can be called minor planets, at worst they’re just lumped together as “KBO”s, or Kuiper Belt Objects.

So where does this leave our poor little friend Pluto? Apparently its discovery in 1930 was nothing more than a lucky mistake. Everyone was looking for a planet, and Pluto just happened to wander into the right photograph at the right time. But now, seventy-six years later, we all know the truth. Pluto was just a pauper pretending to be a prince, a lowly little KBO who found itself sitting at the head table with the rest of the planets. There are those out there who would have Pluto excommunicated, stripped of its title and banished to insignifigance with the rest of the KBOs. But I don’t think that’s going to happen, nor should it. Everyone alive today has grown up with the idea that there are nine planets. Pluto may be known as the smallest, but it’s still part of the club. There’s nothing to gain by demoting Pluto, by teaching schoolkids that there are only eight planets. In essence, Pluto has been grandfathered in, and it will always be considered one of the nine old men of the solar system, even if it doesn’t really belong there.

And that’s why we’re sending a spacecraft to Pluto. First of all, there’s just the ego of the human spirit. We have eight notches on our interplanetary bedpost, but there’s room for one more. We need to visit just to say that we’ve been there. But we also need to examine the place up close, and find out for sure what it’s really like. Pluto is just so far away and so small that there’s really only so much you can find out using telescopes alone. Most of what we’ve learned about Pluto over the years have been inferences and guesswork, and most of it has been proven wrong by new advances in technology. The only way to break that cycle is to go there, to see close up exactly how big it is, how many moons it has, what the surface is like, and just what kind of lonely life Pluto has to live way out there at the edge of the solar system.

That’s what New Horizons is going to do. The hunk of metal that is currently balanced on the tip of a rocket in Florida will one day be zooming past Pluto, giving us the answers that we need so badly. But it’s not going to be fast. If New Horizons manages to launch before the end of the month, it will be on course to rendezvous with Pluto in July 2015. That’s over nine years from now. And if it misses the January launch window and gets underway in February, it loses the advantage of a Jupiter gravity assist, which adds another five years to the trip. So even with the launch just hours away, we’re still going to have to wait an interminably long time to get any of our questions answered.

But at least it will be happening. A spacecraft that’s en route is a million times better than one that’s still in the planning stages, or one that still being talked about and waiting for a budget. That’s where we were with this Pluto mission for so long: no definite plans, no definite timetable, just a lot of hot air and no money.

The universe is full of questions. But if tomorrow’s launch goes off as planned, at least we’ll be a little closer to answering some of them.

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