Earth's oldest asteroid impact 'may have ended ice age'


The crater as seen from Barlangi Rock, with an outcrop in its centre



The crater was discovered in the dry outback in 1979, but geologists had not previously tested how old it was. Due to billions of years of erosion, the crater is not visible to the eye. Scientists mapped scars in the area's magnetic field to determine its 70km (43 miles) diameter. To determine when the asteroid hit Earth, the team examined tiny zircon and monazite crystals in the rocks. They were shocked" in the strike and now can be read like "tree rings", Prof Kirkland said. These crystals hold tiny amounts of uranium. Because uranium decays into lead at a consistent pace, the researchers were able to calculate how much time had passed.How did they date it?Scientists have identified the world's oldest asteroid crater in Australia, adding it may explain how the planet was lifted from an ice age. The asteroid hit Yarrabubba in Western Australia about 2.2 billion years ago - making the crater about half the age of Earth, researchers say. Their conclusion was reached by testing minerals found in rocks at the site. The scientists say the find is exciting because it could account for a warming event during that era. The Curtin University research was published in the journal Nature Communications on Wednesday.

A zircon crystal used to date the impact Yarrabubba

These crystals hold tiny amounts of uranium. Because uranium decays into lead at a consistent pace, the researchers were able to calculate how much time had passed. The timing of the impact could also explain why the world warmed around this time, according to the researchers. Read more ...