its mark in the northwest of Australia discovered a gigantic cosmic impact. Where on earth that has just occurred impact is not known.
Demonstrated by geological survey that our planet was hit 3.46 billion years ago by an asteroid with a diameter of 20 to 30 kilometers. In addition, a hundred kilometers wide crater must have formed. However, the geological activity of the earth is of such ancient impact structure no longer be found.
Geologists from the Australian National University under the direction of impact expert Andrew Glikson surveyed cores from ancient sedimentary rocks in Marble Bar. In it they found small glass beads (sferulen), indicating extremely strong heating, as occurs during heavy meteorite impacts. Also, the relative amounts of elements such as platinum, nickel and chromium in the old sediment layers point in the direction of an outer impact.
According Glikson Earth several billion years ago must be taken regularly by asteroids (on the moon are the scars that oerbombardement still visible), and is the handful of ancient impacts that so far identified just the tip of the iceberg. "We have only found evidence for seventeen strikes older than 2.5 billion years, but it would be hundreds," said Glikson.
By Editorial Volkskrant: Govert Schilling / Allesoversterrenkunde.nl Photo: Australian National University
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