Af­ter 20 years of trans­mit­ting amaz­ing pic­tures from Sat­urn and its moons, Nasa’s Cassini makes its fi­nal dive into the ringed planet yes­ter­day.


The Nation - - WORLD -

AF­TER 20 years in space, Nasa’s Cassini space­craft yes­ter­day made an in­ten­tional death plunge into Sat­urn, end­ing a sto­ried mis­sion that sci­en­tists say taught us nearly ev­ery­thing we know about Sat­urn to­day and trans­formed the way we think about life else­where in the so­lar sys­tem.

Cassini, an in­ter­na­tional project that cost $3.9 bil­lion and in­cluded sci­en­tists from 27 na­tions, dis­in­te­grated as it dove into Sat­urn’s at­mos­phere at a speed of 120,700 kilo­me­tres per hour.

Cassini’s fi­nal contact with Earth came at 7.55am. Its des­cent into Sat­urn’s at­mos­phere be­gan 83 min­utes ear­lier, some 1.4 bil­lion kilo­me­tres from Earth.

“The space­craft is gone,” said Cassini pro­gram man­ager Earl Maize of Nasa’s Jet Propul­sion Lab­o­ra­tory.

“Thanks, and farewell faith­ful ex­plorer. But the le­gacy of Cassini has just be­gun,” he told a press con­fer­ence af­ter­ward.

“The ef­fect Cassini has – and will have – on the fu­ture of plan­e­tary ex­plo­ration will go on for decades.”

Cassini’s plunge into the ringed gas gi­ant – the far­thest planet vis­i­ble from Earth with the naked eye—came af­ter the space­craft ran out of rocket fuel af­ter a jour­ney of some 4.9 bil­lion miles (7.9 bil­lion kilo­me­tres).

Its well-planned demise was de­signed to pre­vent any dam­age to Sat­urn’s ocean-bear­ing moons Ti­tan and Ence­ladus, which sci­en­tists want to keep pris­tine for fu­ture ex­plo­ration be­cause they may con­tain some form of life.

“There are in­ter­na­tional treaties that re­quire that we can’t just leave a derelict space­craft in or­bit around a planet like Sat­urn, which has pre­bi­otic moons,” said Maize. “Pre­bi­otic” refers to the con­di­tions or in­gre­di­ents that can oc­cur be­fore life emerges.

Three other space­craft have flown by Sat­urn—Pioneer 11 in 1979, fol­lowed by Voy­ager 1 and 2 in the 1980s.

But none has stud­ied Sat­urn in such de­tail as Cassini, named af­ter the French-Ital­ian as­tronomer Gio­vanni Domenico Cassini, who dis­cov­ered in the 17th cen­tury that Sat­urn had sev­eral moons and a gap be­tween its rings.

“This is the fi­nal chap­ter of an amaz­ing mis­sion, but it’s also a new be­gin­ning,” said Thomas Zur­buchen, as­so­ciate ad­min­is­tra­tor for Nasa’s Sci­ence Mis­sion Direc­torate.

“Cassini’s dis­cov­ery of ocean worlds at Ti­tan and Ence­ladus changed ev­ery­thing, shak­ing our views to the core about sur­pris­ing places to search for po­ten­tial life be­yond Earth.”

Cassini launched from Cape Canaveral, Florida in 1997, then spent seven years in tran­sit fol­lowed by 13 years or­bit­ing Sat­urn. In that time, it dis­cov­ered six more moons around Sat­urn, three-di­men­sional struc­tures tow­er­ing above Sat­urn’s rings, and a gi­ant storm that raged across the planet for nearly a year.

The 22 by 13 foot (6.7 by 4 me­tre) space­craft is also cred­ited with dis­cov­er­ing icy gey­sers erupt­ing from Ence­ladus, and eerie hy­dro­car­bon lakes made of eth­ane and meth­ane on Sat­urn’s largest moon, Ti­tan.

In 2005, the Cassini or­biter re­leased a lan­der called Huy­gens on Ti­tan, mark­ing the first and only such land­ing in the outer so­lar sys­tem, on a ce­les­tial body be­yond the as­ter­oid belt.

Huy­gens was a joint project of the Euro­pean Space Agency, the Ital­ian Space Agency and Nasa. Linda Spilker, Cassini project sci­en­tist, said say­ing farewell to the space­ship felt like “los­ing a friend.”

“For 13 years we have been run­ning a marathon of sci­en­tific dis­cov­ery,” she added.

Eight of the space­craft’s 12 sci­en­tific in­stru­ments were still cap­tur­ing data in Cassini’s last mo­ments as it flew more deeply into Sat­urn than ever, be­fore dis­in­te­grat­ing like a me­teor.

“Who knows how many PhD the­ses might be in just those fi­nal sec­onds of data?” Spilker asked.

Al­ready, some 4,000 sci­en­tific pa­pers have been based on data from the mis­sion, said Mathew Owens, pro­fes­sor of space physics at the Univer­sity of Read­ing, in England.

Michael Watkins, di­rec­tor of Nasa’s Jet Propul­sion Lab­o­ra­tory, de­scribed Cassini’s fate as “not an end but re­ally a be­gin­ning”.

Mem­bers of the Nasa Cassini Mis­sion Team speak at the Jet Propul­sion Lab­o­ra­tory in Pasadena, Cal­i­for­nia, this .

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