World's Oldest Rock?

The Oldest Rock In The World Tells Us A Story : Krulwich Wonders... : NPR

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... It's a zircon, from the Persian word "zargun" meaning "golden colored," an extremely durable mineral found all over the world. This one turned up in a dry, hilly region of Western Australia. It was sitting inside a larger rock, and when scientists checked, it turns out this little grain formed around 4.4 billion years ago. That would make it the oldest rock we've ever seen on this planet, old enough to know secrets about early Earth, old enough to tell us a little something about how life started here.

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After all, this planet, geologists say, is only 4.5 or 4.6 billion years old. So this little grain has been around since almost the beginning but not quite.

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When geochemists Bruce Watson and Mark Harrison looked more closely at this grain, they could see where it "started." Crystals are minerals that grow, or harden from a hotter, liquid state, and this crystal got its start on the lower left, in the spot marked "core."

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Geochemists know that zircons will grab more titanium when it's hotter, less titanium when it's colder, so if you count your titanium concentrations, you can figure out how hot it was when the rock formed: X amount of titanium, for example, means it was 600 degrees Celsius when it grew; Y amount of titanium means it was 350 degrees Celsius. Scientists call this equation "the titanium thermometer."

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So Watson and Harrison counted titanium concentrations in a bunch of these very old zircon grains, matched them to the thermometer, and discovered that when these zircons formed, the temperatures ranged from about 680 degrees Celsius, plus or minus 20.

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Rocks that crystallize at these temperatures have been exposed to water. This is something geologists know. ...

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So, all of a sudden, here was evidence that the red hot, lava-laced, boiling, lifeless Earth of 4.4 billion years ago had water on it! What's more, Watson says, "we feel our results point more strongly toward the idea of surface water."

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Here's why: It is now possible to imagine that life began on Earth almost as soon as the Earth began that life (in the presence of water) is, if not inevitable, at least very insistent. Once you've got a planet with water BINGO!

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If that's true, chances for life in the universe suddenly improve dramatically.

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Here on Earth, life could have formed, been blown away, then formed again and one of those times, down at the bottom of some temporary ocean, sitting by a warm vent it stayed.

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That's what this teeny chip of a rock is now allowing us to think: that life has such potency, such urgency, that as soon as life is possible life happens!

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That's a mighty big story to find in a pebble.

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Hyperbole slightly over the top, but cool info eh?Wonder how they dated the zircon ...Enjoy.

Thread copied to the World's Oldest Rock? thread in the Geology and the Great Flood forum, this copy of the thread has been closed.