[Breaking news update, posted at 8:58 p.m.]
NASA has reestablished contact with its New Horizons spacecraft after a planned communications blackout as the probe makes the first-ever flyby of Pluto.
[Previous story, posted at 7:32 p.m.]
NASA’s New Horizons spacecraft completed a historic flyby of Pluto on Tuesday, becoming the first spacecraft to pass over the small, icy world.
The unmanned piano-size spacecraft went over Pluto at 7:49 a.m. ET, traveling at nearly 31,000 mph about 7,750 miles above Pluto’s surface, NASA said.
It’s the first mission to Pluto and its five moons.
“I have to pinch myself,” said Alice Bowman, the mission’s operations manager. “Look what we accomplished.”
But the drama doesn’t end there.
The probe is busy gathering data and won’t “phone home” to Earth until around 9 p.m. ET.
The wait for the signal is a tense one for mission managers.
“I am feeling a little bit nervous just like you do when you set your child off, but I have absolute confidence that it’s going to do what it has to do what it needs to do to collect that science,” Bowman said at a briefing after the flyby.
Alan Stern, the mission’s principal investigator, said New Horizons should transmit a message back to the Earth for about 20 minutes.
“We’ll find out how it’s doing — whether it survived the passage through the Pluto system. Hopefully it did,” Bowman said. “We’re counting on that. But there’s a little bit of drama because this is true exploration. New Horizons is flying into the unknown.
The planet already is dazzling mission managers. They said Pluto could have been covered in clouds and they wouldn’t have seen much.
But instead, Stern said they’re seeing a world with “various kinds of brightness, very dark regions near the equator, very bright regions just to the north of that and a broad intermediate zone over the pole.”
And there’s snow. Yes, snow.
“Pluto has strong atmospheric cycles. It snows on the surface,” Stern said.
“Pluto has turned out to be an extraordinarily complex, interesting world,” said NASA Associate Administrator John Grunsfeld.
The New Horizons team on Tuesday released the best photos of Pluto that they’ve gathered during its mission. But Wednesday, they expect to release photos from the close encounter, and they’ll continue getting data back from the probe for 16 months.
Scientists on Monday said New Horizons already has settled one debate about Pluto — its size. Information gathered by the probe indicates Pluto is 1,473 miles (2,370 kilometers) in diameter. That’s somewhat bigger than earlier estimates, and it means Pluto is larger than all other known solar system objects beyond the orbit of Neptune.
The Pluto flyby mission completes what NASA calls the reconnaissance of the classical solar system, and it makes the United States the first nation to send a space probe to every planet from Mercury to Pluto. The probe traveled more than 3 billion miles to reach Pluto.
Stern noted that Tuesday’s Pluto flyby came exactly 50 years after the Mariner 4 probe accomplished the first flyby of Mars.
“I think it’s fitting that on that 50th anniversary we complete the initial reconnaissance of the planets with the exploration of Pluto,” he said Tuesday.
Why go to Pluto?
New Horizons looks like a gold foil-covered grand piano. It is 27 inches (0.7 meters) tall, 83 inches (2.1 meters) long and 108 inches (2.7 meters) wide. It weighed 1,054 pounds (478 kilograms) at launch. It has seven instruments on board to map the surfaces of Pluto and its largest moon, Charon. It also is studying their atmospheres.
The spacecraft was launched on January 19, 2006, before the big debate started over Pluto’s status as a planet. In August of that year, the International Astronomical Union reclassified Pluto as a dwarf planet.
But Stern disagrees with the IAU’s decision.
“We’re just learning that a lot of planets are small planets, and we didn’t know that before,” Stern said earlier. “Fact is, in planetary science, objects such as Pluto and the other dwarf planets in the Kuiper Belt are considered planets and called planets in everyday discourse in scientific meetings.”
After surveying Pluto, New Horizons will keep flying, heading deeper into the Kuiper Belt, a region that scientists think is filled with thousands of small, icy objects. NASA and mission managers will decide later this year whether to extend the mission to study another small world in the Kuiper Belt.