Europa’s spew­ing hints at life-friendly en­vi­rons

The Star Malaysia - Star2 - - SCIENCE - By AMINA KHAN

THE icy moon Europa squirts wa­ter like a squishy bath toy when it’s kneaded by Jupiter’s grav­ity – and the Hub­ble Space Tele­scope has caught it in the act.

The data cap­tured by Hub­ble de­pict two huge gey­sers of wa­ter vapour spew­ing out of the moon, prob­a­bly from cracks near its south pole. At 124 miles (200km) high, the gey­sers were tall enough to reach from Los An­ge­les to San Diego.

The dis­cov­ery, de­scribed on Thurs­day in the jour­nal Sci­ence, shows that Europa is still geo­phys­i­cally ac­tive and could hold an en­vi­ron­ment friendly to life.

“It’s ex­cit­ing,” said Lorenz Roth, a plan­e­tary sci­en­tist at the South­west Re­search In­sti­tute in San An­to­nio and one of the lead au­thors of the study, which was pre­sented at a meet­ing of the Amer­i­can Geo­phys­i­cal Union in San Fran­cisco.

Europa isn’t the only squirty moon in our so­lar sys­tem: Saturn’s moon Ence­ladus has been caught spray­ing wa­ter from its south pole out of four par­al­lel frac­tures, a for­ma­tion that sci­en­tists have dubbed “tiger stripes”.

Th­ese pretty plumes are the re­sult of tidal forces. Just as our moon’s grav­ity squeezes and stretches the Earth a bit, caus­ing the oceans to rise and fall, Saturn’s mas­sive grav­i­ta­tional pull squeezes and stretches Ence­ladus.

That causes cracks on its icy sur­face to open and al­lows wa­ter to es­cape, feed­ing the planet’s dif­fuse E ring.

Sci­en­tists have long won­dered whether Jupiter was do­ing some­thing sim­i­lar to Europa. Af­ter all, that moon’s sur­face is only about 65 mil­lion years old, mak­ing it less than 2% as old as the so­lar sys­tem.

Sci­en­tists fig­ured that some geo­phys­i­cal pro­cesses must be go­ing on that are con­stantly re­new­ing the sur­face. But over sev­eral decades, re­searchers re­peat­edly failed to catch the moon in ac­tion, said Robert Pap­palardo, a plan­e­tary sci­en­tist at Nasa’s Jet Propul­sion Lab­o­ra­tory who was not in­volved in the study.

When the Voy­ager space­craft flew by Europa in 1979, it caught a tiny blip on the moon’s edge that ex­perts thought might be a plume, but they couldn’t con­firm their hunch. More than a decade later, the Galileo space­craft saw a po­ten­tial plume of its own. But this turned out to be dig­i­tal residue, traces of a pre­vi­ous im­age, Pap­palardo said.

Even Hub­ble had trou­ble see­ing such plumes un­til space shut­tle as­tro­nauts fixed one of its cam­eras in 2009. Look­ing for wa­ter vapour in the ul­tra­vi­o­let wave­lengths of light still tests the lim­its of Hub­ble’s abil­i­ties, sci­en­tists said.

To catch Europa in the act, Roth and his col­leagues also knew they had to get the tim­ing of their ob­ser­va­tions just right. Ence­ladus re­leases wa­ter when it’s just about as far from Saturn as it can get. So, they made sure to point Hub­ble to­ward Europa when it was most dis­tant from Jupiter, in De­cem­ber 2012.

Sure enough, they caught a pair of plumes bear­ing clear signs of oxy­gen and hy­dro­gen – the com­po­nents of wa­ter vapour – shoot- ing into space from near the south­ern pole. (Also as ex­pected, when Europa was close to Jupiter, there were no plumes to be seen.)

Sci­en­tists can’t say ex­actly where the plumes are com­ing from. They could be re­leases from the ocean of liq­uid wa­ter thought to lie un­der the moon’s frozen sur­face.

But they could also be the re­sult of wa­ter chang­ing di­rectly from ice to gas as Europa’s ice sheets rub against each other.

If the moon is still geo­phys­i­cally ac­tive, that could make it a prime en­vi­ron­ment for life, Pap­palardo said.

Another study re­leased at the meet­ing de­tailed signs of clays on Europa’s sur­face. Clays are of­ten as­so­ci­ated with or­ganic mat­ter, which is why Nasa’s Cu­rios­ity rover is ex­am­in­ing clays on Mars.

The clays on Europa were prob­a­bly brought there by comets or as­ter­oids. If they wound up in Europa’s sub­sur­face ocean, they could have de­liv­ered key in­gre­di­ents for a nu­tri­en­trich soup that might al­low life to emerge.

“We’re try­ing to un­der­stand, ‘Could this be a hab­it­able en­vi­ron­ment to­day? Could there be life there to­day?’” Pap­palardo said.

“The pro­cesses that could per­mit hab­it­abil­ity may be go­ing on now.”

Per­haps fu­ture stud­ies can an­a­lyse the con­tents of Europa’s wa­tery plumes and see if there are any signs of or­ganic mat­ter, Pap­palardo said. A fu­ture space­craft might even fly through a plume and take sam­ples di­rectly. – Los An­ge­les Times / McClatchyTri­bune In­for­ma­tion Ser­vices

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