Monday, February 18, 2008

Europa, oceanul si submarinul

Sci­en­tists hope to send a ro­botic sub­ma­rine in­to oceans that may lurk with­in a moon of Ju­pi­ter, in what could be the first ex­plora­t­ion through li­quid wa­ters on an­oth­er world.
Re­search­ers have long spec­u­lat­ed that un­der the icy shell that en­cases the moon, Eu­ro­pa, liq­uid wa­ter might har­bor prim­i­tive life forms. A Eu­ro­pa mis­sion is still years away, ac­cord­ing to sci­en­tists; but in prepara­t­ion for such an ev­ent, they plan to test a NASA-funded ro­botic probe un­der ice on Earth.
Test­ing will take place next week in Lake Men­do­ta on the cam­pus of the Un­ivers­ity of Wis­con­sin, Mad­i­son, ac­cord­ing to a Feb. 8 an­nounce­ment from the agen­cy. The sub is made to “swim un­teth­ered un­der ice, cre­at­ing three-di­men­sion­al maps of un­derwa­ter en­vi­ron­ments,” the an­nounce­ment said. The ro­bot would al­so “col­lect da­ta on con­di­tions in those en­vi­ron­ments and take sam­ples of mi­cro­bi­al life.” The pro­ject is led by Uni­ver­sity of Illi­nois at Chi­ca­go and NA­SA scientists.

Af­ter the Wis­con­sin tests, re­search­ers said they plan to ship the probe to a per­ma­nently fro­zen lake in Ant­arc­ti­ca for fur­ther tri­als. The ve­hi­cle, called EN­DUR­ANCE (En­vi­ron­men­tally Non-Disturbing Un­der-ice Robotic Ant­arc­tic Ex­plor­er), is a $2.3 mil­lion proj­ect. It’s a fol­low-up to the Deep Phre­at­ic Ther­mal Ex­plor­er, an­oth­er NASA-funded proj­ect that fin­ished un­derwa­ter tests in Mex­i­co in 2007, agen­cy sci­en­tists said. Eu­ro­pa, slightly smaller than Earth’s Moon, is the fourth larg­est of Ju­pi­ter’s at least 16 moons, and is cov­ered with whit­ish and brown ice. Be­neath it, many re­search­ers be­lieve the moon may har­bor the only glob­al ocean of liq­uid wa­ter in our So­lar Sys­tem be­sides Earth’s. Im­ages from NASA’s Gal­i­le­o space­craft have shown ar­eas with si­m­i­lar­i­ties to Earth’s ice-floe cov­ered Arc­tic oceans, sug­gest­ing the ex­ist­ence of wa­ter or warm “s­lushy” ice be­low, ac­cord­ing to Da­vid R. Wil­liams, a sci­ent­ist at the agen­cy’s God­dard Space Flight Cen­ter. Such an ocean could con­ceivably pro­vide a home for liv­ing things.
Eu­ro­pa’s in­te­ri­or is hot­ter than its sur­face, ac­cord­ing to Wil­liam B. McK­in­non, a plan­e­tary sci­ent­ist at Wash­ing­ton Un­ivers­ity in St. Lou­is. This in­ter­nal heat comes from the gravita­t­ional pull of Ju­pi­ter and its oth­er large moons, which stretch Eu­ro­pa’s in­sides in dif­fer­ent di­rec­tions and cre­ate fric­tion. Most of the sat­el­lite is made of rock, ac­cord­ing to McK­in­non.

Re­peat­ed split­ting and shift­ing of the sur­face ice, and dis­rup­tions from be­low, have re­shaped Eu­ro­pa’s sur­face, Mcin­non con­tin­ued. A re­sult is that there are few vis­i­ble im­pact craters, since the shift­ing would have erased these. The sur­face shows shal­low cracks, val­leys, ridges, pits, blis­ters, and icy flows, McK­in­non added, none more than a few hun­dred yards or me­ters high or deep. The Ital­ian as­tron­o­mer Gal­i­le­o discov­ered Eu­ro­pa 1610. Its name is said to have been first sug­gested by his con­tem­po­rary, the Ger­man as­tron­o­mer Kep­ler, who pro­posed nam­ing Ju­pi­ter’s moons af­ter the se­cret mis­tresses of Ju­pi­ter, king of the gods in Greek and Ro­man my­thol­o­gy. Ac­cord­ing to myth, Ju­pi­ter took the form of a bull to ab­duct Eu­ro­pa, a Phoe­ni­cian prin­cess.


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