Comet lan­der’s data weak­ens space mag­netism the­ory


What­ever caused small space rocks to lump to­gether bil­lions of years ago, mag­netism is un­likely to be the rea­son.

Sci­en­tists said Tues­day that mea­sure­ments made by the Euro­pean space probe Phi­lae, which landed on comet 67P in Novem­ber, show the comet’s core isn’t mag­ne­tized.

Some as­tro­physi­cists have sug­gested that mag­netism might have been re­spon­si­ble for align­ing and then bind­ing to­gether rocks into larger boul­ders dur­ing the early stages of planet for­ma­tion.

But in a pa­per pub­lished on­line by the jour­nal Science, the team led by Hans-Ul­rich Auster at the Tech­ni­cal Uni­ver­sity of Braun­schweig, Ger­many, said their data — which ben­e­fited from three un­ex­pected bounces that al­lowed Phi­lae to col­lect more re­sults than planned — don’t sup­port this the­ory.

“If the sur­face was mag­ne­tized, we would have ex­pected to see a clear in­crease in the mag­netic field read­ings as we got closer and closer to the sur­face,” said Auster. “If comet 67P/Churyu­movGerasi­menko is rep­re­sen­ta­tive of all cometary nu­clei, then we sug­gest that mag­netic forces are un­likely to have played a role in the ac­cu­mu­la­tion of plan­e­tary build­ing blocks greater than 1 me­ter feet) in size.”

Al­lan H. Treiman, a se­nior sci­en­tist at the Lu­nar and Plan­e­tary In­sti­tute in Hous­ton, Texas, who wasn’t in­volved in the study, said the re­sults cred­i­bly sug­gest other forces were re­spon­si­ble.

“Auster did not find any mag­netic field, with a very sen­si­tive in­stru­ment, so it seems un­likely that mag­netism in the so­lar ne­bula was sig­nif­i­cant for the col­lec­tion of me­ter-sized ob­jects,” Treiman said in an email. “At that scale, it seems likely that elec­tro­static or grav­i­ta­tional at­trac­tion would be stronger.”

The find­ings are part of a se­ries of sci­en­tific re­sults ob­tained by sci­en­tists an­a­lyz­ing data col­lected by the Phi­lae lan­der and its moth­er­ship Rosetta, which is fly­ing along­side the comet on its el­lip­ti­cal or­bit around the sun.



The com­bi­na­tion of pho­tos taken by the Nav­cam of the Rosetta space probe and re­leased by the Euro­pean Space Agency ESA on Mon­day, April 13.

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