Color data revealed that Pluto is reddish in places—“weirdly Martian” as one scientist put it.
Color data revealed that Pluto is reddish in places—“weirdly Martian,” as one scientist put it.Image by SwRI/APL/NASA

Soon after the New Horizons spacecraft made its closest approach to Pluto, at 7:49 A.M. on Tuesday—seventy-two seconds ahead of schedule, after a nine-and-a-half-year journey—Bonnie Buratti, one of the mission’s scientists, told me that she had been worried that the dwarf planet “would be a bit bland.” NASA had even booked the magician David Blaine to entertain the crowd that gathered at mission control, at the Johns Hopkins University Applied Physics Laboratory, in suburban Maryland, just in case the first high-resolution images proved insufficiently wondrous. As it happened, Buratti’s concern was unfounded. Even the New Horizons team, dedicated Plutophiles all, seemed astonished when the images came in. “This is a psychedelic Pluto,” Cathy Olkin, the mission’s deputy project scientist, told me. Kimberly Ennico-Smith, the science team’s co-investigator, tweeted a double exponent: “WowWowWow.” Alan Stern, the principal investigator, called the photos “mouthwatering.”

More images have begun streaming in this morning. Even at the speed of light, signals from New Horizons take around four and a half hours to travel the three billion miles back to Earth, and the download rate makes a dial-up modem seem positively zippy. Indeed, although the closest approach took place on Tuesday morning, it wasn’t until that night, at 8:52 P.M., that the team found out that their spacecraft had survived the flyby. There were hugs, high-fives, speeches, standing ovations, and some tears. But the team’s work was far from over. So much information was gathered during the maneuver that it will take sixteen months to return it all to Earth, and longer still to analyze it. Soon, we will have images of Pluto’s surface so detailed that, if they were of Earth, you could pick out the ponds in Manhattan’s Central Park. With those images will come detailed topographical information, composition data, and atmospheric readings. We will find out whether Pluto has visible rings; whether it shares an atmosphere with Charon, its largest moon; whether it has clouds or haze; whether it hosts a deep subsurface ocean or active geology; and much, much more.

Not so long ago, Pluto was little more than a blurry cluster of pixels. When the New Horizons team set out to map the mission’s trajectory, they discovered that no one knew precisely where Pluto was; its orbit takes so long (two hundred and forty-eight Earth years) that humankind had been capable of observing only about a third of it, and the best guesses as to its distance from the sun had a six-thousand-mile margin of error. Glen Fountain, the New Horizons project manager, compared the challenge of hitting the team’s target window to a golfer, standing in New York City, sinking a hole-in-one on a golf course in suburban Los Angeles. “We have managed that so well that even I don’t believe it,” he said.

The mission was designed, built, and tested in forty-two months (record time, by aerospace standards) in order for New Horizons to take advantage of Jupiter’s gravity to slingshot itself toward Pluto. If it had missed this rendezvous, the journey would have taken an additional four years. The launch took place in January, 2006, with the relatively small spacecraft—“a concert grand piano with a giant salad bowl on top,” as one of its designers fondly described it to me—hitched to the Atlas V, one of NASA’s most powerful rockets.* Once New Horizons passed Jupiter, more than a year later, its trajectory would take it past nothing of real scientific interest until Pluto. For another eight years, it would sail through the solar system at thirty-one thousand miles per hour.

Merely reaching its destination was not the only challenge that New Horizons faced. Alan Stern’s application for a time slot on the Hubble Space Telescope, to scope out hazards in the Pluto system, was rejected repeatedly. It wasn’t until an equipment failure on Hubble led to an unexpected cancellation that his team got their chance. When they did, seven months before launch, they discovered that Pluto had two previously unobserved moons, Nix and Hydra. Then, as New Horizons got closer, they spotted two more—Styx and Kerberos—adding to the tally of objects that the spacecraft would have to both observe and avoid crashing into. The flyby was carefully re-choreographed: rather than simply gazing at Pluto and Charon, New Horizons would have to shift its attention continuously, refocussing its seven instruments on six different celestial bodies, like a Ritalin-deprived teen-ager. Engineers calculated that the chance of a debris strike was just one in ten thousand, but even something the size of a grain of rice could have blown a hole in New Horizons at the speed it was moving. The radio silence during Tuesday’s flyby, combined with the knowledge that ninety-nine per cent of the mission’s data remained on the spacecraft, made the fourteen hours between closest approach and nighttime check-in feel almost as long as the years it took to get to Pluto.

As they sifted through the measurements and images received on Tuesday, Stern and his colleagues reported that Pluto does, as they suspected, have a polar ice cap. It is composed of frozen methane and nitrogen, which sublimate into the atmosphere during the warmer periods of the dwarf planet’s orbit, returning to the ground as frost and snow. “I think you could, in fact, have a good snowball fight on Pluto,” Bill McKinnon, the mission’s geology and geophysics lead, said. (He noted, however, that methane ice is softer than water ice, which might limit skiing opportunities.) A cratered section of the surface appeared to be billions of years old, showing a history of impacts, while other areas seemed much younger, with chasms, hummocks, and eroded ridges that might indicate either tectonic processes or atmospheric erosion. Color data revealed that Pluto is reddish in places—“weirdly Martian,” as Fran Bagenal, who oversees plasma and particle observations, put it—which led to speculation that certain darker patches, at the equator, could consist of a tarry gunk of irradiated hydrocarbons known as tholin. This is “prebiotic material,” Bonnie Burrati said, meaning that it contains some of the chemical precursors for life.

As the scientists traced tendrils of reddish brown and speculated as to the rate of melt at the edge of a two-toned ice patch near Pluto’s equator, the impossibly distant world came to life. Fed up with referring to features as, for instance, “the black circle at two o’clock” and “the big white patch,” the team had started to give them names—first nicknames, such as “the heart” and “the whale,” and then unofficial but more formal names drawn from the mythology of the underworld. The whale became Lovecraft’s Cthulhu, and a nearby dark smudge was christened Balrog, after the demons of Tolkien’s Middle-earth. An alien landscape had started to become a collection of places: knowable, if not yet known.

Although its mission has been accomplished, the spacecraft’s journey is not yet over. In the next several years, if all goes well, New Horizons will travel deep into the Kuiper Belt, a relatively recently discovered ring of small, icy bodies orbiting the sun in a dense cloud. This is the solar system’s dark and mysterious edgeland, where fossil remnants of its beginnings have been preserved as if in a giant freezer. Scientists hope that, by offering us a window back more than four and a half billion years, the objects in the Kuiper Belt—Pluto among them—will help us explain Earth’s origins, and perhaps our own. In August, Stern will choose which of two as yet unnamed objects to visit next. He estimates that the spacecraft will be able to keep recording and transmitting until the mid-twenty-thirties. Then its plutonium power source will run out and it will shut down, sailing onward alone into deep space.

*Owing to an editing error, an earlier version of this sentence misidentified the Atlas V as NASA’s most powerful rocket.