Nearly 3.5 billion miles from home, an intrepid spacecraft on the final leg of its streak to Pluto's front door is expected to rendezvous with the planetary dwarf on July 14.
The New Horizons mission -- the longest space voyage ever -- is the last great American flyby of an alien world. Traveling at warp speed in a nine-year hurtle toward Pluto, the spacecraft has entered its so-called encounter phase.
Clocking in at 1,054 pounds -- about 3,000 pounds lighter than a Jeep Wrangler -- the probe is crossing what the mission's lead scientist calls "Pluto's front yard." Already, the first images are being beamed back. The team is counting down the days. All systems are go.
Pluto -- a dwarf planet and possibly the most controversial one in the known universe -- may hold some of the deepest secrets about the solar system: how Earth's oceans filled with water and possibly how life here emerged. Some scientists think the mission may determine whether Pluto -- kicked out of the solar system in 2006 -- will be welcomed back. Others are convinced it's out of the family for good.
"This mission makes the hair on the back of my neck stand up," said Susan Rose of East Meadow, president of the Amateur Observers Society of New York, an organization of citizen astronomers. The society is affiliated with the Custer Institute and Observatory in Southold. A minor "planetary body" in the asteroid belt discovered by California scientists was named in her honor.
"We all came from exploding stars, so this mission, which is going farther than any other, is a way to learn about ourselves," she said.
Theory holds that every atom on Earth, from those that comprise DNA to the atoms that make up trees, rocks, even Earth's iron core, came from the stardust of violently exploding supernovae. When the gargantuan stars erupted and died, they rained debris throughout the cosmos. Some of that evidence may persist on Pluto unscathed, some scientists say.
The mission's top scientist, however, has no idea what to expect. "We really don't know what we'll learn because we've never been there," said New Horizons' principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. He's certain, however, that eavesdropping on Pluto will yield more information during the flyby than scientists have gathered in 85 years.
"Nothing like this has ever happened. This mission to Pluto is the last picture show," Stern said. "It's a capstone event."
'Into the unknown'
He describes the voyage as "the longest complete journey into the unknown."
"This isn't just a mission to a planet but a mission to whole new class of planet," said Stern, a planetary scientist. "We're turning the spotlight on Pluto," added Stern, possibly the most ardent proponent for reinstating Pluto to full planetary status.
"All over the surface we'll map the geology. We will be doing this for Pluto and all of its moons -- all six bodies. And if there are new moons to be discovered, we'll find those, too."
Stern's institute and the Johns Hopkins Applied Physics Laboratory built the spacecraft and are collaborating with NASA on the groundbreaking journey.
The entire mission, including the probe's cost, ran about $700 million, NASA estimates show. The probe's cameras begin the first Pluto mapping exercises three months from closest approach when it is 65 million miles away. At closest approach in July the tiny craft will swoop within 7,750 miles of Pluto and 17,900 miles of its largest moon.
"This spacecraft is about the size of a baby grand piano, but it's much more powerful than those that take up an entire room," Stern said.
Starting in the 1970s and continuing into this century, U.S. probes have visited Earth's kin: the terrestrial planets, the gas giants and the distant and dark ice giants.
Left unvisited until now is dinky and demoted Pluto, an orb smaller than our moon and cast on the farthest fringes of the solar system, deep in the Kuiper belt -- the frigid deep freeze where comets are born.
Pluto is orbited by at least five moons and is believed to be the once widely sought Planet X, the subject of sky searches dating to the 19th century.
Planet X's existence seemed settled with Pluto's 1930 discovery. But by the 1970s, scientists began wrestling with the definition of a planet, and in September 2006 -- nine months after New Horizons' launch -- the International Astronomical Union voted Pluto out of the fold.
"Pluto isn't like any of the planets in our solar system," said Fred Walter, professor of astronomy at Stony Brook University.
Walter argues that there are dozens upon dozens of bodies in the Kuiper belt that are more like Pluto and less like solar system planets. He doubts evidence is forthcoming to reverse Pluto's status.
Could be a twin
Some scientists contend Pluto may not even be a single planet but a twin with Charon, one of its moons. If that's the case, the pair would effectively be "a dwarf double planet," these scientists say.
Others refer to Pluto as a trans-Neptunian object, and also note a gravitational link between Pluto and Neptune. Most just call it dwarf planet.
Said Stern: "A dwarf planet is still a planet," countering those who say Pluto is too small, odd and far away to make the full-fledged planet grade.
Stern calls the upcoming flyby a Christmas present in July that's bound to change hearts and minds.
Other mission experts say just sending an "eye" into an alien world makes a journey so deep into the cosmos worthwhile. "From a NASA perspective we don't care what it's called," said Jim Green, director of NASA's Planetary Science Division.
"It's a member, along with a number of other bodies that we know absolutely nothing about," Green added. "It's a cold, icy world and we anticipate that Pluto and its satellites have a huge amount of water and ices."
Scientists, he said, want to know how these bodies formed and what role they may have played in the solar system's evolution and whether there may be any links to life on Earth.
"When we went to the moon and brought back moon rocks we saw two ages. Some were 4.5 billion years old and then a series of new rocks that were formed around 3.8 billion years ago, about the time life started here on Earth.
"What does that mean?" Green asked. It's theorized, he said, that about 3.8 billion years ago Kuiper belt objects -- most likely comets -- brought water to Earth and aided in the development of life.
Pluto may help science unlock long-held secrets of the universe, Green said.
Stern, meanwhile, is pumped because his mission to Pluto is likely to answer a range of questions.
"We know it has seasons and polar caps and that its atmosphere is mostly nitrogen like Earth's atmosphere and that's it. We are going into a very wide-open moment of discovery."