‘Alien ice’ cre­ated on Earth for first time

China Daily (Hong Kong) - - LIFE -

WASH­ING­TON — A strange form of ice has been cap­tured be­ing frozen from wa­ter in real time on Earth for the first time, US re­searchers said on Tues­day.

In a study pub­lished on­line in the US jour­nal Phys­i­cal Re­view Let­ters, re­searchers at the Stan­ford Univer­sity de­scribed how Ice VII, or Ice Seven, which nor­mally forms in en­vi­ron­ments such as when icy plan­e­tary bod­ies col­lide, was cre­ated and im­aged in the lab in just bil­lionths of a sec­ond.

“These ex­per­i­ments with wa­ter are the first of their kind, al­low­ing us to wit­ness a fun­da­men­tal dis­or­der-to-or­der tran­si­tion in one of the most abun­dant mol­e­cules in the uni­verse,” says the study’s lead au­thor, Ari­anna Glea­son, a post­doc­toral fel­low at Los Alamos Na­tional Lab­o­ra­tory and a vis­it­ing sci­en­tist in the Ex­treme En­vi­ron­ments Lab­o­ra­tory of Stan­ford’s School of Earth, En­ergy & En­vi­ron­men­tal Sci­ences.

Un­der reg­u­lar con­di­tions on our planet’s sur­face, wa­ter crys­tal­lizes in only one way, dubbed Ice Ih or sim­ply hexag­o­nal ice, whether in glaciers or ice cube trays in the freezer.

To cre­ate Ice VII, Stan­ford re­searchers used the Linac Co­her­ent Light Source, the world’s most pow­er­ful X-ray laser.

First, the team beamed an in­tense, green-col­ored laser at a small tar­get con­tain­ing a sam­ple of liq­uid wa­ter. The laser in­stantly va­por­ized lay­ers of di­a­mond on one side of the tar­get, gen­er­at­ing a rocket-like force that com­pressed the wa­ter to pres­sures ex­ceed­ing 50,000 times that of Earth’s at­mos­phere at sea level.

As the wa­ter com­pacted, a sec­ond beam from an in­stru­ment called the X-ray Free Elec­tron Laser ar­rived in a series of bright pulses, each of which lasts only a fem­tosec­ond, or a quadrillionth of a sec­ond. Akin to cam­era flashes, this X-ray laser snapped a set of im­ages on the pro­gres­sion of molec­u­lar changes as the pres­sur­ized wa­ter crys­tal­lized into Ice VII.

The phase change took just six bil­lionths of a sec­ond, or nanosec­onds, and dur­ing this process, the wa­ter mol­e­cules bonded into rod shapes, and not spheres as the­ory pre­dicted, the re­searchers say.

Delv­ing into ex­trater­res­trial ice types, in­clud­ing Ice VII, will help sci­en­tists model such re­mote en­vi­ron­ments as comet im­pacts, the in­ter­nal struc­tures of po­ten­tially life­sup­port­ing, wa­ter-filled moons like Jupiter’s Europa, and the dy­nam­ics of jumbo, rocky, oceanic ex­o­plan­ets called su­per-Earths.

“Any icy satel­lite or plan­e­tary in­te­rior is in­ti­mately con­nected to the ob­ject’s sur­face,” Glea­son says. “Learn­ing about these icy in­te­ri­ors will help us un­der­stand how the worlds in our so­lar sys­tem formed and how at least one of them, so far as we know, came to have all the nec­es­sary char­ac­ter­is­tics for life.”

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