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Il pianeta terra non viene colpito ogni 26 milioni di anni da asteroidi, come suggeriva uno studio americano del 2015. Alcuni ricercatori del politecnico di Zurigo (ETHZ) hanno confutato questa tesi, dibattuta in astronomia ormai da 30 anni.
Mathias Meier del Poli, e il suo ex-dottorando Sanna Holm-Alwmark dell’Università svedese di Lund, hanno ripercorso la storia degli impatti degli ultimi 500 milioni di anni, momento dell’apparizione delle prime forme di vita complesse, concentrandosi in particolare su 22 crateri oggetto di una datazione precisa. Risultato: nessuna accumulazione periodica riscontrabile.
Alcune cadute di oggetti spaziali sono state anzi pressoché simultanee, ciò che potrebbe aver indotto in errore gli scienziati americani, spiegano gli studiosi dell’ETHZ. Inoltre sono state rettificate anche alcune datazioni che risultavano sbagliate. Le conclusioni dello studio sono state pubblicate nella rivista britannica "Monthly Notices of the Royal Astronomical Society".
ATS/dielle
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