Let’s take a trip. A long trip, to the very edge of our neighborhood- the Solar System. All the way to Pluto. Why Pluto? It’s the most well-known yet unexplored place in our Solar System, and it can teach us something about planetary formation and our own world. The icy dwarf planets like Pluto and its neighbors in the Kuiper belt are the kind of objects out of which the larger planets formed. Pluto is the closest and most familiar of the dwarf planets. We’ve sent probes to all the other planets, at least once. Pluto remains a distant mystery, seen only by Earth-based telescopes and the Hubble Space Telescope…
That’s the best picture we have of Pluto, which took 4 years of processing data from the Hubble to construct. It’s that small. It was reclassified as a dwarf planet in 2008 since it has some odd characteristics shared with none of the other larger planets, and in turn lacks some of their key features. Regardless of what we call it, it’s still the same mysterious place, out there with it’s strangely tilted orbit, several tiny companion moons, and a year that is as long as 248 years on Earth.
So why have we never gone to Pluto for a closer look? With limited resources, NASA naturally picked locations that were more scientifically interesting when planetary exploration began; the inner planets Mercury, Venus, and Mars, and the gas giants Jupiter, Saturn, Uranus, and Neptune. By the late 1980s, we had learned a good bit more about Pluto and the far reaches of the solar system, and serious interest in a mission began to grow. We saw active geysers on Triton, one of Neptune’s moons, similar to and just a little larger than Pluto itself. Maybe these ice-ball moon-sized objects were a lot more interesting than we originally suspected.
And then there are the technical difficulties. You’d want a spacecraft that carried enough instrumentation to make the trip worthwhile, and yet light enough to be sent all the way to Pluto. While the Voyager probes have already gone much farther than Pluto, they’ve been out there over 30 years and their flight paths didn’t take them near Pluto itself. They had a primary mission to see the big outer planets. The fact that Voyager 1’s faint signal can still be picked up from just past the edge of the Solar System is a bonus. It’s another challenge altogether to send something to Pluto as the first stop. And that’s because Pluto is very, very far from Earth.
For comparison, let’s start with a planet we’ve already visited. Jupiter is an average distance of 489 million miles from Earth. In 1972 it took the Pioneer 10 mission, traveling a direct orbit, 22 months to make that trip. Pluto is over 7 times further away, an average of 3.78 billion miles. To get there in any reasonable time, we’ve got to go fast. And NASA had to decide to go soon; Pluto is at the point in its orbit where it is moving further and further from the Sun, meaning it will be darker and harder to see, and it’s atmosphere will freeze and be harder to analyze.
36,373 miles per hour. By any standard we’re used to, that’s fast. It’s almost too fast to wrap your head around. Sometimes it’s easier to picture distance than speed, so let’s try it this way. Think of two places that are 10 miles apart. Two small towns near you, perhaps. If you’re in the Nashville area, that’s about the driving distance from downtown to the Brentwood exit on I-65. At 36,373 mph, you’ll make that trip in one second. The New Horizons mission to Pluto reached that speed and broke the record for the highest launch velocity from Earth when it took off on January 19, 2006. It was also the first spacecraft launched directly into a Solar System escape trajectory. In other words, NASA swung for the fences.
Launching something that fast is, um, rocket science, but the concept is simple; put the smallest probe you can build on the biggest rocket you have. Specifically, an Atlas V with 5 extra solid fuel boosters and 3 stages. NASA had previously never used more than 3 boosters on an Atlas V launch, and a 3rd stage is rare. Once the big rocket is used up you fire a second smaller one, and then the final one. All that raw thrust plus a spacecraft that weighs just over 1000 pounds equals ZOOM. The Pioneer probe made it to Jupiter in 22 months; New Horizons got there in 13. Before that it had to pass the Moon’s orbit, which in did in 9 hours. The previous record for a fly-by was held by the Soviet Luna 1 probe, which made the trip in 36 hours in 1959.
New Horizons went to Jupiter first so it could get a gravity boost from the huge planet. This maneuver cuts 3 years off the trip to Pluto. It approached at just the right angle and distance so that Jupiter’s gravity pulled it in faster and faster, but didn’t trap it into orbit. It reached 52,000 mph, then left the encounter aimed for Pluto, like a perfectly angled pool shot. See ya!
Instrument tests are always in order during these missions, so New Horizons sent back some pics from the Jupiter fly-by. Jupiter’s four biggest moons took center stage. Interesting fact- see that dusty spray at the top of Io’s picture? It’s from a volcano. Io is one of the most volcanically active places in the Solar System, far more so than Earth.
What about pics of Pluto? There aren’t any yet. New Horizons won’t arrive until July 2015, which should give you an even better idea of the distances involved. Almost 8 years after a super fast launch and a 52,000 mph kick in the pants from Jupiter, it still has a year and a half to go.
You can see this for yourself- the Johns Hopkins’ Applied Physics Laboratory maintains a page that has near real-time data on New Horizons’ location.
If all goes well during the Pluto encounter, it will spend 4 years exploring the Kuiper belt, an asteroid belt similar to the one between Mars and Jupiter but several times larger. If it is still functioning in the year 2038, it may join Voyager 1 in transmitting data from the edge of the Heliosphere, the bubble created by the Sun’s magnetic field, where interstellar space begins.
If I seem enamored with this little spacecraft and its mission, you’re exactly right. I love the audacity of it, sending something such a long way, having the patience to wait 9 1/2 years and the hopefulness that it will arrive intact. I’m reminded of Charles Lindbergh making the first non-stop transatlantic flight. And now there’s this probe, the size of a baby grand piano, hurtling through an environment that is more immense and empty than any of us can honestly grasp. In Chuck Yeager’s autobiography, he says a sharp pilot with the best eyesight can see 10 miles on a clear day. Just 10. And when are we ever in a truly empty environment here on Earth? Space, even within our Solar System, is beyond our experience and bigger than we can conceive. We use numbers because we have to, words and even imagination aren’t enough.
It is amazing to me that we did this. Humans. Put this speedy spacecraft out there as an extension to our own eyes and ears, already so far from us, and we can talk to it, send instructions, get back pictures and surface scans and chemical analyses and all the other things it’s designed to do. And from over 3 billion miles away, guide it right to Pluto like the most amazing shot ever made.
And just as amazing, I can sit here on Earth with my laptop, click a link, and see where it is. In May of 2015 it will be close enough to Pluto to send back pictures that exceed the Hubble’s best resolution. In July of that year when it’s sending back data from it’s closest approach, don’t expect me to answer the phone.
In case the above video won’t play, you can try Wikipedia’s version here