PLUTO AND ITS MOON CHARON AS SEEN FROM THE HUBBLE TELESCOPE

NASA is asking for public comment on The New Horizons Mission to the planet Pluto. The reason? NASA will be using a tiny amount of plutonium to power the spacecraft:

The New Horizons mission will use a plutonium-powered radioisotope thermoelectric generator for power in deep space, where sunlight isn’t intense enough to run the spacecraft. It’s like the generators that flew in the Cassini probe now at Saturn. In fact, it’s Cassini’s spare.

“RTGs have a proven track record and safety record,” Kurt Lindstrom, NASA’s executive for the mission, said in a press conference today at Kennedy Space Center.

The thermoelectric generator is one of those inventions that you might slap yourself on the head and say “Why didn’t I think of that!” It uses heat generated from the plutonium and turns that heat into electrcity. The atoms in plutonium are so energetic that if you were to hold a clump of the stuff in your hand, you could actually feel the heat.

Then again, if you’re dumb enough to hold the stuff you’d be dead in a couple of days. Plutonium is the most toxic substance known to man. A grain smaller than a pinhead lodged in your lungs would give you cancer and you’d be dead in six months.

That being said, we’ve used similar technology for more than 30 years. The problem isn’t with the technology; it’s with how we get the darn thing up in space in the first place.

Here’s a risk profile for the mission:

There’s a 93.8 percent chance of a successful launch, the statement says; a 5.8 percent chance of an accident with no release of radiological material; and 0.4 percent chance of a mishap with a radiological release

I’m not quite sure how they reached that 0.4% chance of radiological release but given how the environmentalists almost scuttled the Cassini mission over the same issue, you can bet it’s based on pretty good science.

The mission itself sounds fascinating. Pluto is without a doubt the strangest “planet” in the solar system. I put the word planet in quotes because recently, there’s been a rather lively debate about whether or not Pluto can be considered a real planet.

Scientists settled on the idea that since Pluto has been referred to as a planet for so long, it should remain that way. It turns out that thousands of kids wrote to the IAU (International Astronomical Union) and begged the adults to keep Pluto as a planet. Even scientists can’t resist when kids get involved.

That being said, Pluto is weird. It’s very small – less than 1/5 the size of Earth – with gravity that’s 2 1/2 times less than on our moon. Speaking of moons, Pluto’s satelite Charon is half the size of it’s mother planet! The two bodies do a strange gravitational dance around each other that scientists are still scratching their heads trying to figure out.

Pluto’s orbit is highly irregular. It careens around the solar system like a drunken sailor, passing inside the orbit of Neptune (thus for a time making Neptune the most distant planet) as well as orbiting in the opposite direction than the rest of the planets.

Pluto is also the only planet in the solar system we haven’t visited. That will change if NASA gets the go ahead for the New Horizons mission. The plan is to launch next January, get a gravitiy assist from Jupiter which will slingshot the craft towards the outer planets in 2007, and initiate a flyby of Pluto in 2015, coming within 10,000 km of the planet and 50,000 km of Charon. Then the spacecraft will swing out towards the mysterious Kuiper Belt where some of the most bizarre objects in the solar system can be found.

Plans for this extended mission include one to two encounters of Kuiper Belt Objects, ranging from about 25 to 55 miles (40 to 90 kilometers) in diameter. What are these objects? They’re the flotsam and jetsam left over from the creation of the solar system, after the planets formed from our sun’s accretion disk.

If all goes well, just about the time I’m ready to start collecting one of my pensions (I’ve got two!), human beings will get their first look at the surface of this world that its discoverer Clyde Tombaugh named after the God of the Underworld.