Folosind un instrument ce poate debloca secretelr sistemului solar, s-a descoperit o noua tehnica ce determina precis varsta meteoritilor., raporteaza oamenii de stiinta in revista Nature.
Oamenii de stiinta nu se inteleg i privinta estimarii varstelor meteoritilor pentru ca este greu sa distingi perioada in care rocile s-au format si perioada in care ele au fost arse dintr-un impact si au zburat prin spatiu spre Pamant.
Geologul de la UCLA Axel Schmitt si coleii sai au inceput prin examinarea structurii cristalelor minerale ale meteoritului, care variaza, in funcite de doua criterii. Cristalele se pot forma prin solidificare gradata intr-un flux de lava sau se formeaza rapid in urma caldurii si presiunii impactului. Apoi au determinat varsta cristalelo prin masurarea ratiei de uraniu ce trebuie dusa/condusa. Uraniul are doi izotopi, fiecare descompunandu-se in propiul izotop conducator, oferind cercetatorilor multiple masuratori pe baza datarii radioactive ce verifica consistenta.
Echipa a analizat meteoritul martian si au gasit cristale mari, conectate, cu o varsta de cca 187 milioane de ani, fapt ce sugereaza ca roca s-a format acum aprox.187 mil ani in urma unei eruptii vulcanice.
Cercetatoriiau gasit cristale de zircon care s-au format intr-un impact acum aprox. 22 milioane de ani.
Schmitt spune ca prin aplicarea tehnicii pe rocile de pe marte, pe luna, pe asteroizi sau chiar pe Pamant oamenii de stiinta pot afla mai multe despre timpul in care au erupt vulcanii in trecutul indepartat.
Providing a tool for unlocking secrets of the early solar system, a new technique accurately determines the age of meteorites, scientists report in the July 25 Nature.
Scientists disagree over estimates of meteorites’ ages because it’s hard to distinguish between when the rocks formed and when they got seared from an impact and flung into space toward Earth.
UCLA geochronologist Axel Schmitt and colleagues began by examining the structure of a meteorite’s mineral crystals, which differs depending on whether the crystals solidified gradually within a lava flow or rapidly after the intense heat and pressure of an impact. Then they determined the age of the crystals by measuring the ratio of uranium to lead. Uranium has two isotopes, each of which decays into its own lead isotope, providing researchers with multiple radioactive-dating measurements to cross-check for consistency.
The team analyzed the Martian meteorite Northwest Africa 5298 and found large, interlocking crystals about 187 million years old, which suggests that the rock formed during a volcanic eruption back then. The researchers also found zircon crystals that likely formed from an impact no more than 22 million years ago.
Schmitt says that by applying the technique to rocks from Mars, the moon, asteroids and even Earth, scientists can learn about when volcanoes erupted in the distant past.
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