Study: Moon Europa cov­ered in ice spikes

South Florida Sun-Sentinel (Sunday) - - Movies - BY ARNOLD PEARLSTEIN Arnold Pearlstein is un­avail­able; his col­umn will re­sume when he re­turns. By Ben Guar­ino

Few moons in the so­lar sys­tem are as in­trigu­ing as Jupiter’s moon Europa. A global ocean of salt wa­ter al­most cer­tainly sur­rounds the moon — and it holds more wa­ter than any ocean on Earth. Above this im­mense sea, where sur­face tem­per­a­tures dip to mi­nus 300 de­grees Fahren­heit, a crust of wa­ter ice forms a shell. As­tronomers pre­dict that Jupiter, which bom­bards the moon with in­tense ra­di­a­tion, causes the en­tire moon to groan with grav­ity’s tug. Europa’s liq­uid wa­ter is a tempt­ing tar­get for fu­ture mis­sions look­ing for pos­si­ble alien mi­crobes.

But be­fore a fu­ture lan­der can search for mi­cro­scopic E.T., the probe might have to con­tend with a for­est of tall, jagged ice spikes. So ar­gues a team of plan­e­tary sci­en­tists and ge­o­mor­phol­o­gists in the jour­nal Na­ture Geo­science. Their re­search sug­gests Europa is an icy hedge­hog world, cov­ered in ice for­ma­tions rarely found on Earth.

On our planet, ice takes sev­eral forms, as var­ied as nee­dle ice, rime, park­ing lot slush and more ex­otic lumps. But be­cause Europa’s sur­face is “in­cred­i­bly cold,” said Daniel Hob­ley, a ge­o­mor­phol­o­gist at Cardiff Univer­sity in the U.K., an au­thor of the study, ice will not melt and re­freeze.

In­stead, stranger things hap­pen. Ice is not per­fectly flat — it’s made of lit­tle crys­tals. “Each of those crys­tals has po­ten­tial to lens light,” Hob­ley said, chan­nel­ing or re­fract­ing light down into ice. Over mil­lions of years, en­er­gized by the sun’s ra­di­a­tion, Europa’s ice trans­forms into gas.

Hob­ley and his col­leagues con­sid­ered where on Earth might ap­prox­i­mate Europa. They landed on the An­des, the South Amer­i­can moun­tain range that stretches from Venezuela to Ar­gentina. At the high­est peaks, the An­des has ice that, in win­ter, stays too cold to melt. What’s more, near the equa­tor, the sun’s an­gle is high and con­stant, just like it is over Europa’s mid­dle.

In the An­des, Hob­ley and his co-au­thors knew, an ice for­ma­tion called pen­i­tentes takes shape. Pen­i­tentes are named af­ter an Easter re­li­gious fes­ti­val, prac­ticed by some Span­ish-speak­ing Chris­tians, in which monks wear pointed white hats (the “pen­i­tent,” hence, pen­i­tentes).

At moun­tain tops, the sun’s light carves pits deep in the ice, leav­ing be­hind tall blades. Pen­i­tentes do not form at high lat­i­tudes be­cause the sun is too low in the sky in win­ter; the ice crys­tals do not fun­nel the light so sharply down­ward.

The bot­tom of these tri­an­gu­lar cav­i­ties get hot­ter, and the sides stay cool. On Europa, they would grow “crazy, crazy slow,” Hob­ley said, at about a foot ev­ery mil­lion years. But be­cause Europa’s sur­face has been largely un­changed for 50 mil­lion years, “they’ve got a nice long time to do it.” Europa’s pen­i­tentes, the au­thors cal­cu­lated, could be al­most 50 feet long.

Newspapers in English

Newspapers from USA

© PressReader. All rights reserved.