A sci­en­tist solves an H2O mys­tery with pro­found im­pli­ca­tions for sci­ence

Newsweek - - Contents - BY JES­SICA WAPNER @jes­si­cawap­ner

An H20 Mys­tery Solved

de­spite our ut­ter de­pen­dence on it, wa­ter is a mys­tery. Sci­en­tists don’t un­der­stand why it ex­pands as it cools, why hot wa­ter turns to ice faster than cold wa­ter or its ex­tra­or­di­nary sur­face ten­sion, which al­lows it to cling to soil and sup­port in­sects. “It’s al­most like wa­ter is try­ing to hide its secrets,” says John Russo, a math­e­ma­ti­cian at the Univer­sity of Bris­tol in Eng­land, who thinks he may have fig­ured one out.

Most sci­en­tists seek­ing to parse wa­ter’s odd­i­ties ex­pose it to ex­treme con­di­tions, such as very low tem­per­a­tures. Russo and col­leagues at the Univer­sity of Tokyo took a dif­fer­ent ap­proach, cre­at­ing com­puter mod­els of “ex­treme wa­ter,” as he de­scribes it. In their sim­u­la­tion, they al­tered the bonds that hold the mol­e­cules to­gether un­til they be­gan be­hav­ing like a more nor­mal liq­uid. “We switched off the strange­ness,” says Russo. The team could then see what bond struc­tures were nec­es­sary for the anoma­lous be­hav­ior. When sim­u­lated ice no longer floated, for ex­am­ple, the team knew they’d elim­i­nated the struc­ture re­spon­si­ble for that pe­cu­liar trait.

Their con­clu­sion was as sur­pris­ing as their sub­ject. “You should re­ally think of wa­ter as two sep­a­rate liq­uids mixed to­gether,” says Russo. The dif­fer­ence be­tween them: the hy­dro­gen bonds hold­ing the mol­e­cules to­gether. In one, four are ar­ranged in an or­ga­nized, sym­met­ri­cal tetra­he­dron—a pyra­mid with four faces. In the other, the pyra­mids are dis­or­dered and in­ter­con­nected. Wa­ter, it seems, is equal parts or­der and chaos—a po­etic re­sult for Earth’s most valuable re­source.

The find­ing, pub­lished in April in the Pro­ceed­ings of the Na­tional Academy of Sciences, could in­flu­ence the cli­mate change mod­els that pre­dict how warm­ing tem­per­a­tures will alter our world. “Wa­ter matters for the ba­sic physics of the way cli­mate works,” says Chris Milly, a hy­drol­o­gist with the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion. The way wa­ter crys­tals form in clouds is not well un­der­stood, for ex­am­ple, yet the crys­tals de­ter­mine how much sun­light clouds will re­flect back into space, a cal­cu­la­tion that matters when it comes to mod­el­ing fu­ture warm­ing.

Milly says ex­plain­ing wa­ter’s weird be­hav­ior isn’t as im­por­tant as sim­ply know­ing that it ex­ists, which means the two-liq­uid the­ory may not im­prove cli­mate mod­els. But that’s just one po­ten­tial ap­pli­ca­tion. Cry­op­reser­va­tion (freez­ing tis­sue) and many fun­da­men­tal bi­o­log­i­cal pro­cesses rely on wa­ter’s bizarre prop­er­ties. Russo hopes fur­ther re­search will re­veal more secrets.

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