Rosetta’s long jour­ney ends in a cloud of dust

Baltimore Sun - - NATION & WORLD - By Deb­o­rah Net­burn

The Rosetta mis­sion to catch up with a speed­ing comet, land a space probe on it and fol­low it as it flies past the sun has of­fi­cially come to an end.

Early Fri­day morn­ing, the Euro­pean Space Agency’s Rosetta or­biter com­mit­ted op­er­a­tional sui­cide when it de­lib­er­ately smashed onto the sur­face of 67P/Churyu­mov- Gerasi­menko, the moun­tain-sized comet that has been its con­stant com­pan­ion for the last two years.

The crash was slow but still fatal.

The mis­sion’s lan­der, Phi­lae, was built with legs, springs and har­poons to help it land on a comet and sur­vive. The Rosetta or­biter was de­signed to fly around 67P, not touch down on the sur­face.

There were no cam­eras to record Rosetta’s fi­nal mo­ments, but ESA en­gi­neers said the space­craft prob­a­bly bounced a few times given the comet’s low grav­ity. In the process, it prob­a­bly kicked up a cloud of dark, dry dust be­fore set­tling in its fi­nal rest­ing place on the smaller of the comet’s two lobes.

“At the mo­ment of im­pact, Rosetta will be crushed,” flight direc­tor An­drea Ac­co­mazzo said dur­ing the mis­sion’s fi­nal hours. “It will re­main on the comet for­ever be­cause there is no way to get it off the sur­face.”

But this death dive was not made in vain.

Mis­sion plan­ners at ESA put Rosetta to work un­til the last pos­si­ble sec­ond, pro­gram­ming it to col­lect high-res­o­lu­tion data from closer to the comet’s sur­face than ever be­fore.

Rosetta was not the first space mis­sion to study a comet, but it was the first to get to know one. Fly­ing along­side 67P for nearly two years, it was able to ob­serve En­gi­neers at the Euro­pean Space Op­er­a­tions Cen­tre man­age the de­scent of the Rosetta probe on Fri­day. how the comet evolved and changed as it trav­eled to­ward the sun and then re­treated to the outer so­lar sys­tem.

“It’s been a tremen­dously suc­cess­ful mis­sion,” said Paul Weiss­man, a comet sci­en­tist at the Plan­e­tary Science In­sti­tute in Tuc­son, who worked on Rosetta for 20 years. “Our plan was to ren­dezvous with the comet far from the sun and then watch its ac­tiv­ity grow and die back down, and that’s ex­actly what hap­pened.”

The 11 in­stru­ments on Rosetta were de­signed to ob­serve many as­pects of the comet. They mapped its phys­i­cal sur­face fea­tures, sniffed the cloud of gas and dust around its nu­cleus, an­a­lyzed its in­ter­ac­tion with the so­lar wind and used ra­dio waves to probe its in­te­rior.

Sci­en­tists hope their study of 67P will re­veal clues about the ori­gin of the so­lar sys­tem and the be­gin­ning of life on Earth.

Re­searchers say the comet formed 4.6 bil­lion years ago, at the dawn of the so­lar sys­tem. Be­cause it has spent nearly its en­tire life in a deep freeze, the frozen mol­e­cules trapped in its nu­cleus could of­fer hints about the com­po­si­tion of the pre-so­lar neb­ula from which the sun and all the plan­ets formed.

Comets like 67P may have brought the molec­u­lar build­ing blocks for life to our planet.

Rosetta’s trav­els with 67P be­gan in Au­gust 2014, af­ter a con­vo­luted 10-year jour­ney across 4.9 bil­lion miles of space.

At the time of their first en­counter, the 2.5-mile­long comet was still in the cold re­gions of the so­lar sys­tem, 335 mil­lion miles from the sun.

To put that in con­text, the Earth is about 93 mil­lion miles from the sun; Jupiter, on av­er­age, is 483.8 mil­lion miles away.

Rosetta sent the Phi­lae lan­der down to the comet’s nu­cleus in Novem­ber 2014, mak­ing it the first probe to touch a comet and live to tell about it. It bounced twice be­fore beam­ing three days’ worth of data back to sci­en­tists on Earth.

Rosetta con­tin­ued to ac­com­pany 67P as it flew closer to the sun. Un­der the or­biter’s watch­ful eye, the comet grew more ac­tive as the warmth of the sun caused frozen ices in the nu­cleus to sub­li­mate and turn into gas jets that shot off the comet’s sur­face.

ESA sci­en­tists re­port that when the or­biter first ap­proached the comet, it was re­leas­ing about 300 grams of water va­por per sec­ond, the equiv­a­lent of two small glasses of water.

DANIEL ROLAND/GETTY-AFP

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