Cassini spacecraft makes death plunge into Saturn after 20-year journey

Traci Watson, Special for USA TODAY | USA TODAY

Show Caption Hide Caption See Cassini's most stunning images of Saturn NASA's Cassini spacecraft gave us the best views of Saturn mankind has ever seen.

The spacecraft lost, but science won.

The vaunted Cassini spacecraft was vaporized Friday as it streaked through Saturn’s atmosphere at 76,000 mph, ending a career that revolutionized scientists’ understanding of the ringed planet and its moons. But even during its final moments, the spacecraft was collecting intelligence and beaming it back to Earth, where researchers quickly began poring over it.

The last radio signal from Cassini to NASA’s giant antenna in Canberra, Australia, was received at 7:55 am ET, 30 seconds later than projected. The spacecraft was not expected to survive more than a minute after it lost touch with Earth.

Though NASA could have chosen to keep Cassini hanging around, managers chose to plunge it into the depths of Saturn, where the spacecraft could gather data on the planet’s composition and magnetic field that are available nowhere else.

The craft’s disintegration in the ringed planet’s atmosphere “was by far the best option -- Cassini going out with an empty tank of gas, at the very top of its game, in a scientifically unexplored area,” Cassini program manager Earl Maize of NASA’s Jet Propulsion Laboratory in Pasadena, Calif, said.

There were tears, handshakes and hugs in the control room after the spacecraft went quiet. Scientists, most watching the events from the nearby campus of the California Institute of Technology, applauded in respect and gratitude. But the mood was somber. “I’ve been working on Cassini for 20 years,” Amanda Hendrix, a senior scientist at the Planetary Institute, said from the Caltech viewing area. “So it’s like losing a member of the family.”

As the spacecraft plunged into Saturn like a meteor, it was buffeted by its passage through the ever-thickening atmosphere. Its tiny thrusters would have fired frantically to try to right the craft, but all such efforts would have been quickly overpowered.

The spacecraft would have started to tumble, then break apart, then melt, first the aluminum and Mylar components and finally the canisters holding the plutonium pellets that provided electrical power. Nothing would have remained, and the spacecraft is now part of the planet it studied for more than a decade. Among its last missives to Earth were data depicting the spot that became its grave.

By the time its last words were received on Earth, the spacecraft had already succumbed to the brutal gravitational forces of its dive into Saturn. The signal from Saturn needed nearly 90 minutes to reach Earth, which means that the spacecraft’s actual final moment was roughly 6:32 am ET.

The craft was out of fuel, and NASA opted to destroy it in Saturn’s churning gases for science’s sake. If left alone, Cassini might have accidentally sprinkled Earthly microbes on Saturn’s moons, which are now considered some of the solar system’s most likely incubators for life.

The realization that Saturn’s moons are ripe for life is courtesy of Cassini itself. With the spacecraft’s exit, such revelations are less likely. No new missions to Saturn are on the books, though such missions are under consideration. Cassini made Saturn “as familiar as our neighborhood,” said Cassini project scientist Linda Spilker of the Jet Propulsion Laboratory, but now “it’s a very distant world. … Those details of rings, those tiny moons snuggled up so close– those are all gone until we go back.”

In the meantime, scientists can busy themselves with the rich archive of data – more than 600 gigabytes’ worth -- collected by Cassini since its arrival at Saturn in 2004, 6-1/2 years after the NASA craft launched from Cape Canaveral, Fla., carrying the European Huygens probe on its back.

In a brilliant career, Cassini racked up six new named moons orbiting Saturn and captured some of the stuff making up the rings. It revealed that both Titan and Enceladus harbor expansive oceans. And it showed that the ocean on Enceladus is warm and laced with chemicals that could nourish life. Thanks to Cassini, Spilker said, scientists realize that life might blossom in places once thought inhospitable.

Not content with the data it had already delivered, Cassini gathered even more as it sped towards annihilation. Eight of its 12 scientific monitors were on alert during the final plunge, sending observations back to Earth until the communication link was lost.

“To the very end, the spacecraft did everything we asked,” Maize said. “Thanks and farewell, faithful explorer.”