Alan Stern: The Man Who Flew Mankind to Pluto : Kyle Peterson
http://www.wsj.com/articles/the-man-who-flew-mankind-to-pluto-1437174709
The New Horizons leader on how the mission succeeded, what the distant planet revealed, and where the probe is going next.
Laurel, Md. Pluto is alive—and no one knows why.
On Tuesday the New Horizons spacecraft, having traveled three billion miles since 2006, darted past this orb of rock and ice, gathering data and taking photographs. The first high-resolution shots beamed home showed mountains of water ice roughly the size of the Rockies, and a smooth area without impact craters.
That indicates the section of the planet’s surface is young, renewed and reformed by geological activity. “The solar system, meaning also Pluto, is four and a half billion years old,” Alan Stern, the scientist in charge of the mission, tells me during a Thursday interview. “Already—and this is loose, we can do better later—we can show that surface is less than 100 million years old.”
But geological processes require heat, and therein lies the riddle. “There’s no really good model for how these small planets can have their engines running after four billion years. As planets get smaller, the ratio of surface area compared to their mass goes up. That means that they can’t trap the heat inside very long. They cool off.”
He gestures to the paper cup of coffee on the table in front of him. A small cup of coffee will go cold faster than a large one; a large cup of coffee will go cold faster than a big pot. The point is that without an outside source of energy, such as tidal forces from a nearby gas giant, a planet like Pluto, which is one-sixth the size of our moon and circles the outer reaches of our solar system, should be long dead.
“It’s a complete mystery. This was the first test case. We’ve established something fundamental in planetary science,” Mr. Stern says. “In one fell swoop, in 10 minutes, we got the image, we knew: Everything changed.”
Indeed it did. Pluto was discovered in 1930, when astronomer Clyde Tombaugh, looking at two photographs of the same stretch of sky, spotted a speck of light that had moved. In the 85 years since, scientists slowly added to what was known about the planet, its moons, its odd, cockeyed orbit. Yet Pluto itself remained little more than a pinprick in the dark, too small and distant for even the Hubble Space Telescope to make out clearly.
Then New Horizons began to approach. The craft has been described as roughly the size and shape of a baby grand piano—albeit one wrapped in foil and topped with a seven-foot satellite dish. It’s outfitted with an array of sensors, and powered (appropriately enough) by a plutonium battery. On Monday the spacecraft snapped the image of Pluto that seems set to stick: a haunting, ruddy brown sphere with a bright white birthmark in the shape of a heart.
When we meet two days after the flyby at the Johns Hopkins University Applied Physics Laboratory, which built and commanded the New Horizons craft, Mr. Stern has not gotten much sleep. But he is possessed by such energy that it’s hard not to wonder whether he, too, might be powered by plutonium.
Mr. Stern says he first started advocating a trip to Pluto in 1989, and after several false starts NASA decided in 2000 to have an open competition. The space agency had begun conducting smaller missions this way in the early 1990s, pitting proposals against one another and putting a scientist outside of NASA in charge of the resulting projects.
But the mission to Pluto would be the most expensive one to follow this model, and the first to the outer planets. “NASA has done about 15 missions with scientists in charge. The farthest one has gone three times as far from the sun as the Earth is,” Mr. Stern says. “We went 33 times as far.” In that sense, New Horizons might help prove that big, successful space missions don’t have to be directed from Washington and run from the top down.
The team led by Mr. Stern was selected in 2001, and he says the structure—and memories of mission proposals canceled for budgetary reasons—enforced discipline on the New Horizons project. “There’s going to be a lot of ‘noes,’ because we’re going to stay on price and we’re going to stay on schedule,” he says he told his team. “We’re going to do a really good mission, but you know what, it’s going to have to be necessarily compromised in some ways, because we’re trying to break the mold.” The final cost: $720 million.
Similarly, Mr. Stern is a fan of private spaceflight. “I think that that’s an important coming wave. And it’s great because it means it’s a new source of capital. Competition rocks,” he says. “When the private sector started putting communications satellites in earth orbit, there was one company, and now there’s like literally 30 and it’s a $50 billion a year market.”
So now for the question every third-grade graduate is bursting to ask the man who just buzzed Pluto: Is it a planet or not? This is a vexed subject, but Mr. Stern is resoundingly in the “yes” camp.
Recall that in 2006 the International Astronomical Union knocked Pluto off its official planetary pedestal. Pluto had always been considered a misfit, hewing to neither the archetype of the rocky inner planets, nor to that of the outer gas giants. Whereas the other eight planets orbit in nearly concentric circles, Pluto loops through space following an off-center ellipse. But the breaking point for Pluto’s stature came only when scientists began finding worlds even farther away. Eris, for instance, which is approximately the same size as Pluto, was discovered in 2005.
At that point it seems that the choice became whether to drop Pluto or to welcome untold numbers of newbies into the planetary pantheon. Those voting at the IAU meeting chose the former option, to public consternation. Without Pluto, the mnemonic that millions of American schoolchildren had learned to remember the planets, “My Very Educated Mother Just Served Us Nine Pizzas” suddenly looked half-baked.
But the alternative was an ever-growing mnemonic periodically appended with new words to accommodate discoveries. “We’re not so keen to have Pluto and all his friends in the club because it gets crowded,” one IAU scientist commented. “By the end of the decade, we would have had 100 planets, and I think people would have said, ‘My goodness, what a mess they made back in 2006.’ ”
Mr. Stern objects. “That’s a very 20th-century view. Our technology used to be very limited, we could only see a few planets, so we could memorize the list, because we thought we knew them all.” Arbitrarily limiting the number of planets to a familiar few is like deciding to name only seven mountains on Earth, he says.
He also dissents on technical grounds. The IAU claims a bona fide planet must have gravitationally swept its neighborhood clear of other objects, which Pluto hasn’t done. But Mr. Stern says that this definition makes planetary status relative. A celestial body big enough to clear a small orbit and qualify as a planet might not make the cut in a larger orbit, he says. In other words, when is a planet not a planet? When it’s somewhere else.
Pluto is a planet, Mr. Stern maintains, simply because it is massive enough that gravity forces it into a round shape. Under that definition, Ceres, the biggest item in the asteroid belt, is a planet, too. So is our moon. Mr. Stern says that planetary scientists routinely use the term this way, though he doesn’t expect the IAU to reconsider.
“They’re the wrong people,” he says. “I know the public thinks we’re all the same because we study things in space. So my analogy is doctors. There’s lots of kinds of doctors. Would you let a podiatrist do brain surgery on you? Wrong specialty. Don’t let an astronomer classify planets.”
New Horizons, that plucky little probe, isn’t done yet. With a data-transmission speed only a slight fraction of those offered by old dial-up modems, it will take more than a year simply to transmit all the gathered data, and longer for scientists to analyze it. “It’s going to take a small army to get through all this,” Mr. Stern says.
A news conference at NASA on Friday offered tantalizing speculation of the bounty to come. Do the initial images show wind erosion at work? Could the geological activity include geysers? How fast is Pluto’s atmosphere bleeding into space? The answers, once they come, could provide clues to understanding the formation and composition of the solar system.
Meanwhile, Mr. Stern hopes to steer the craft toward a flyby with one of the smaller objects farther out that fall within its range. The plutonium power supply is expected to last another 20 years. Even after it eventually fails and communication is lost, New Horizons will glide on, carrying the American flag out of our solar system and into the black.
But the main mission—at last putting a face on Pluto after 85 years of anonymity—is almost completed.
“People on this project, a lot of them were crying the other night. And when I looked at my social media, all these other people were telling me that they were crying,” Mr. Stern says. “I was a little boy when Neil Armstrong landed on the moon and it was like that. People were crying all around the country. There were tons of stories about people having these emotional reactions.”
Then he pauses for a moment before adding: “We did it. Just three words: We did it.”
Mr. Peterson is an associate editorial features editor at the Journal.
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