In what is being called a "flawless" mission, the NASA spacecraft New Horizons this week successfully performed the first-ever flyby exploration of Pluto after a nine-year and 3-billion mile voyage -- a success met with cheers by scientists and the public gathered at NASA Ames Research Center in Mountain View.
The New Horizons probe produced the first up-close images of the icy dwarf planet which are astounding the astronomy world. More data is expected to be transmitted over the coming months for researchers to pore over.
But like all space exploration missions, there was a significant element of uncertainty. The critical test came on Tuesday, July 14, as the probe went silent to collect data as it crossed Pluto from a distance of about 7,800 miles.
At the NASA Ames at Moffett Field, hundreds gathered to watch the outcome, including several scientists involved in the mission. New Horizons' ground operations were centered at the John Hopkins Applied Physics Laboratory in Maryland, but the events were live-streamed for the Ames attendees.
Just before 6 p.m., the onlookers burst into cheers as mission operations manager Alice Bowman announced the probe had transmitted its "phone home" signal.
"We have a healthy spacecraft," she said. "And we're outbound from Pluto. We did it."
With the successful visit to Pluto, NASA scientists celebrated a new milestone exploring all nine planets of the solar system. The probe, powered by heat from radioactive plutonium-238, is expected to continue functioning for 20 years. It will continue traveling farther out into the Kuiper belt, the outer region of the solar system.
Even though New Horizons has already encountered Pluto, its primary objective to gather data and send it back to Earth remains a work in progress. Radio waves from the probe can transmit at a data speed of only one to four kilobytes a second. At the best rate, it would take just under a half-hour to send an mp3 file, for example.
Measuring about the size of a baby grand piano, New Horizons was outfitted with a variety of analysis equipment, including an infrared scanner, radiometer and an array of spectrometers. NASA officials say they expect to gradually receive the full payload of photos and other data from New Horizons' flyby of Pluto over the next 16 months. For now, the few images of Pluto already sent back by the probe have caused a sensation among astronomers.
"We've arrived at exactly the right time in exactly the right place and turned the camera on," described Dale Cruikshank, a NASA Planetary Scientist. "As far as anyone can tell, it's gone absolutely flawless."
There were many surprises in the new visuals of Pluto, which showed a reddish planet with sharp boundaries between light and dark areas. Cruikshank opined that the red color likely came from organic material -- not a sign of life, he assured. Methane could be broken up by the sun's cosmic rays and reformed into complex hydrocarbons, which might explain the distinctive color, he said.
In many ways, the early data confirmed what scientists already knew about Pluto's physical makeup, including the presence of nitrogen ice and ethane ice. But some questions prompted by the images -- such as what causes the dark regions on the planet surface -- will for now remain mysteries.
Geologists and other experts will be poring over the information for months to come, Cruikshank assured. In fact, just one day after the event, NASA officials announced their latest images appeared to show an icy mountain range rising as high as 11,000 feet on Pluto's surface.
Despite years of preparations, a countless number of things could have gone wrong for the New Horizons mission. Traveling across the solar system at about 36,000 miles per hour, the probe could have been seriously damaged by no more than a "speck of dust," explained Michael Bicay, the Ames director of science.
"Exploring space is hard, and failure comes as often as success," he said. "This (was) the first point at which we understand if the spacecraft survives its journey or not."
In fact, for every successful space mission, such as the Galileo or Curiosity, there are roughly an equal number of explorations that didn't pan out. Taking Mars, the most-visited planet, Bicay pointed out that 47 total explorations have been attempted by NASA and its Russian counterpart -- but only 21 were deemed successful.
But interestingly enough, some successful missions far surpass what the original planners' envisioned. The Voyager II probe, which famously made the only visit to Uranus and Neptune, still remains operational and continues to send back data after 37 years of journeying through space.
With New Horizons, the NASA team had to be very conservative about what items they could include on the voyage, but they did have a little room for sentimentality. Among the science gadgetry, engineers also packaged a CD-rom with the names of all of the NASA team members as well as a few other small items.
The spacecraft included the ashes of Clyde Tombaugh, the U.S. astronomer who originally discovered Pluto in 1930. The NASA team sent one other token -- a 1991 U.S. postal stamp proclaiming: "Pluto: Not Yet Explored".
NASA officials have already pressed the U.S. Postal Service to issue a new stamp to correct the record.