An in-depth study of Saturn

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NASA's Cassini space­craft ended its 20-year mis­sion by crash­ing into Saturn’s at­mos­phere on Fri­day. It took Cassini seven years to reach Saturn af­ter its 1997 launch and it ex­plored the ringed planet and its many moons for 13 years. On Fri­day, it con­tin­ued to trans­mit data and pho­tos to Earth for as long as pos­si­ble be­fore break­ing up and va­por­iz­ing.

CAPE CANAVERAL, Florida — NASA’s Cassini space­craft at Saturn com­pleted its death plunge on Fri­day, fol­low­ing a re­mark­able jour­ney of 20 years.

Cassini plunged through Saturn’s at­mos­phere and va­por­ize like a me­teor. Flight con­trollers at Cal­i­for­nia’s Jet Propul­sion Lab­o­ra­tory had ex­pected one last burst of sci­en­tific data from Cassini, be­fore the ra­dio waves go flat and the space­craft falls silent.

While sad­dened like ev­ery­one else, pro­gram man­ager Earl Maize said he felt great pride and couldn’t have asked for more from “such an in­cred­i­ble ma­chine”.

The only space­craft to ever or­bit Saturn, Cassini showed us the planet, its rings and moons up close in all their glory. Per­haps most tan­ta­liz­ingly, ocean worlds were un­veiled by Cassini and its hitch­hik­ing com­pan­ion, the Huy­gens lan­der, on the moons Ence­ladus and Ti­tan, which could pos­si­bly har­bor life.

“We’ve left the world in­formed but still won­der­ing,” Maize said ear­lier this week. “We’ve got to go back. We know it.”

Cassini was du­ti­ful into the fi­nal hours, tak­ing one last batch of pic­tures be­fore its fi­nal job: sam­pling the at­mos­phere at the gas gi­ant and spew­ing the data back to Earth.

The space­craft was ex­pected to tum­ble out of con­trol while plum­met­ing at 122,000 km/h. Pro­ject of­fi­cials in­vited ground te­le­scopes to look for Cassini’s last-gasp flash, but weren’t hope­ful it would be spot­ted from more than a bil­lion kilo­me­ters away.

Con­fir­ma­tion that Cassini had burned up was ex­pected just be­fore 8 am EDT. It takes 83 min­utes for a sig­nal from the space­craft to reach Earth.

This Grand Fi­nale, as NASA calls it, came about as Cassini’s fuel tank started get­ting low af­ter 13 years ex­plor­ing the planet. Sci­en­tists wanted to pre­vent Cassini from crash­ing into Ence­ladus or Ti­tan and con­tam­i­nat­ing those pris­tine worlds. And so in April, Cassini was di­rected into the pre­vi­ously un­ex­plored gap be­tween Saturn’s cloud tops and the rings. Twenty-two times, Cassini en­tered the gap and came out again. The last time was last week.

Maize said all the staff would be on hand “as our faith­ful trav­eler from Earth makes its fi­nal good­bye”. Their farewells al­ready said, team mem­bers planned to raise their glasses in a fi­nal salute.

The leader of Cassini’s imag­ing team, Carolyn Porco, a vis­it­ing scholar at the Uni­ver­sity of Cal­i­for­nia, Berke­ley, was so in­volved with the mis­sion for so long that she con­sid­ered it “the start of life, part two”.

Cassini de­parted Earth in 1997 and ar­rived at the so­lar sys­tem’s sec­ond-largest planet in 2004. The Euro­pean Huy­gens landed on big moon Ti­tan in 2005. Noth­ing from Earth has landed far­ther.

In all, Cassini col­lected more than 453,000 images and trav­eled 7.9 bil­lion kilo­me­ters. It was an in­ter­na­tional en­deavor, with 27 na­tions tak­ing part. The fi­nal price tag was $3.9 bil­lion.

Six new moons dis­cov­ered

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