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Oldest material on Earth

Oldest material on Earth
Oldest material on Earth A) An image of the Australian continent showing the location of Jack Hills, the source of the oldest material on Earth. B) An image (taken by a technique called cathodoluminescence) of the oldest material known on Earth, a zircon crystal that has been dated to be 4.4 billion years old. Each identified bright or dark interface represents an overgrowth over original crystal and would likely have a different age. How many overgrowths can you spot? 'D' are disturbed regions. It is by dating hundreds of such zircon grains that a re-setting signal is observed around 3.9 billion years, which could be representing the effect of late heavy bombardment. A) NASA / Robert Simmon / Reto St&ouml;ckli; B) <a href="http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2075.html">Valley et al. (2014)</a>