NASA's Galileo spacecraft was purposely destroyed today, ending its scientific career in a blaze of glory, disintegrating at high altitude within Jupiter's turbulent atmosphere.

Its propellant gauge reading near empty, the nuclear-powered spacecraft was put to rest in a 21^st century form of techno-euthansia. The spacecraft fell silent at 12:40:51 p.m. Pacific Time.

It was a good run, as spacecraft go. Dispatched from a space shuttle in 1989, Galileo began its orbiting of Jupiter and its entourage of moons in late 1995. Over the years, the spacecraft relayed an astounding set of observations.

Mission controllers at the Jet Propulsion Laboratory (JPL) in Pasadena, California closely monitored Galileo's final seconds. "Go Galileo, go," became one mantra as the craft grew ever closer to the massive planet.

"This was a team that would not accept defeat. Every difficulty they found a way around it. We had a fantastic team that just pulled off engineering miracles," Lopes said. She joined the Galileo project in 1991, leaving the mission in 2002.

Over the lifetime of the program, perhaps as many as a couple thousand individuals -- including university scientists and students -- worked on Galileo, Lopes said.

In its final output of data, Galileo's radio signals took some 52 minutes to crackle thorough space and reach the Earth.

During its last gasp of scientific sleuthing, Galileo was ordered to use its star scanner to specially measure Jupiter's tiny moon, Amalthea. Galileo's previous flyby of this small body on November 5, 2002, the star scanner caught flashes of light.

There is speculation that those flashes might indicate the presence of rocky debris circling Jupiter in the vicinity of the satellite. While Galileo wasn't near Amalthea during its last pass, the measurement may help confirm or constrain the extent of this hypothesized orbital debris.

Scientists are now trying to ascertain if the star tracker was successful in acquiring the hoped for data, Lopes said.

Claudia Alexander, the 7^th and final Galileo project manager at JPL, was misty-eyed as the spacecraft vaporized over Jupiter.

"I just can't believe the spacecraft collected science data all the way in. I'm just in a state of shock. It's wonderful and can't wait to get that data here on lab and take a look at it. That's going to be some completely unique data," she said.

Shortly after the spacecraft dead-ended at Jupiter, CalTech's Andrew Ingersol, a scientist on the Galileo project, saluted the mission and all those involved, but added: "Another hero is the Jupiter system. It had more surprises, better stuff, just waiting to be discovered than we could have ever imagined. Jupiter and its satellites came through for us."

JPL's Alexander said that, in some respects, the demise of the $1.5 billion Galileo mission is a sad event. "But I think, in general, there's a feeling that it really is time to move on," she said.

"It really is surprising and cool that we've been able to extend the lifetime of this little spacecraft for so long, and make it continue to yield up the secrets of Jupiter," Alexander said. Galileo's longevity at the giant planet, and its scientific output, is a testament to dispatching big, robust spacecraft to various destinations, she added.

"You don't have to wait for 10 more years for the spacecraft to come along that will have the x, y, and z instrument that will allow you to really learn that final thing," Alexander said. Having one probe tote along an armada of instruments permits the switching of scientific gears on the spot in response to new data, rather than waiting for a return mission, she said.

JPL Director, Charles Elachi, congratulated the Galileo team. "I think today we're here not to mourn Galileo but celebrate its accomplishments and recommit ourselves to build on its legacy."

NASA Administrator, Sean O'Keefe, phoned in his thanks to the gathered Galileo scientists and engineers at JPL shortly after the spacecraft impacted Jupiter.

"This is not an end by any means but another chapter in that long continuum of great achievements that have been possible," O'Keefe said. "We've managed to extract 4 times as much as anybody ever reasonably expected we could over the span of a better part of 14 years."

O'Keefe pointed to a new project on the books that will continue the exploration of Jupiter and several of the planet's moons. The Jupiter Icy Moons Orbiter (JIMO), the flagship mission under the auspices of the Prometheus project, will "expand upon the great achievements that the Galileo project has already provided for us and take it to entirely different heights," he said.

The NASA chief also pointed out one twist of fate. Next year, the shuttle program's return to flight vehicle will be Atlantis. That's the same orbiter that sent Galileo on its way to Jupiter.

Although Galileo's mission could have gone on longer, JPL's Alexander noted, if the craft had been left in orbit around Jupiter, the spacecraft's trajectory could have been perturbed - perhaps enough so that it could accidentally crash into something.

That "something", for example, might have been Europa.

Galileo's finding of a purported subsurface ocean on Europa have led many scientists to speculate about the moon as a possible locale for life.

Furthermore, Galileo was not tasked as a life-detection mission. Therefore, the spacecraft did not undergo rigorous sterilization steps like those mandated for Mars-bound vehicles. Hitchhiking microbes from Earth are surely onboard Galileo.

"Basically, in order not to have foreign material introduced into this sensitive environment [of Europa] -- a potential habitat for life -- a decision was made to dispose of this flight hardware by flying it directly into Jupiter itself," Alexander said.

In fact, under the heading "disposition of flight hardware," the September 1988 Planetary Protection Plan for the Galileo spacecraft contained a provision that specified that, if the Planetary Protection Officer determined a Jovian satellite needed protecting, then the Galileo Project would negotiate an end-of-mission to preclude impact with that satellite.

"Galileo has been a spectacularly successful mission, and a real story of accomplishment by the men and women of the Project," said John Rummel, NASA's Planetary Protection Officer at NASA Headquarters in Washington, D.C.

"Galileo's success is amply demonstrated by the fact that it discovered something so significant--an ocean--that we immediately knew we would have to take strict measures to protect it, and thereby preserve a chance to learn about possible life elsewhere in this solar system," Rummel told SPACE.com.

Nose-diving a spacecraft into a destructive collision with a planet on purpose is not new.

NASA's Magellan spacecraft made a dramatic ending to its highly successful mission at Venus when it was commanded to plunge into the planet's dense atmosphere on October 11, 1994.

Purpose of destroying Magellan -- along with saving money -- was to gain data on the planet's atmosphere and on the performance of the spacecraft as it descended. Data collected by Magellan while it circled Venus included radar-mapping 98 percent of the cloud-veiled world during its four year tour-of-duty.

Another probe, NASA's Lunar Prospector, made a controlled crash on the Moon, impacting near the south pole on July 31, 1999. The hope was to look for evidence of water ice, stirred up by the collision, but none was detected.

The Galileo has been labeled as "one of mankind's greatest voyages" by Robert Park, a scientist at the University of Maryland.

Writing in his web site column sponsored by The American Physical Society, Park underscored Galileo's string of robotic revelations.

"It's the sort of thing you can do with robots -- you don't have to bring them home," Park said.

"Galileo discovered liquid water under the frozen oceans of Europa, Ganymede and Callisto. Could this subsurface water, protected from radiation, harbor alien life? The search for life to which we are not related is the most exciting scientific quest of our time. To explore where no human can ever set foot is our greatest adventure," Park said.