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La presenza di ossigeno sulla Terra non è stata cruciale per la sua evoluzione. Le prime forme di vita animale sarebbero comparse centinaia di milioni di anni prima che gli oceani e l'atmosfera si arricchissero del prezioso elemento. Lo indicano nuove analisi geochimiche delle lave di antiche eruzioni sottomarine, pubblicate sulla rivista Nature.
I ricercatori dell'Università della California a Berkeley, studiando l'ossidazione del ferro nelle rocce basaltiche di eruzioni sottomarine hanno notato che la transizione a un mondo con elevati livelli di ossigeno negli oceani è avvenuta tra 540 e 420 milioni di anni fa, molto tempo dopo la comparsa delle prime forme animali, datata tra 800 e 700 milioni di anni fa.
"Se questo risultato verrà confermato, si tratta di uno stravolgimento delle nostre conoscenze sull'evoluzione della vita", ha spiegato John Brucato, astrobiologo dell'Osservatorio di Arcetri dell'Istituto nazionale italiano di astrofisica. "L'abbondanza di ossigeno nell'atmosfera di altri pianeti – ha aggiunto - potrebbe non essere più un'impronta digitale della presenza di vita evoluta".
ATS/AnP
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