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A photo of the 4.4 billion-year old zircon. (John Valley / University of Wisconsin-Madison)

This Little Gem Is the Oldest Piece of the Earth We’ve Ever Found

A tiny zircon from western Australia is 4.4 billion years old

smithsonian.com

This tiny piece of early Earth, a piece of the mineral zircon, dates to 4.374 billion years ago. In the scheme of cosmic time, that's not so long after the planet was born, roughly 4.56 billion years ago. This piece comes from the Jack Hills, an inland range north of Perth, in western Australia. 

Writing in Nature, says MIT geologist Samuel Bowring,“It is no surprise that zircon is the oldest known mineral on Earth, as it is highly resistant to modification and can survive multiple cycles of weathering, transport and re-deposition, and so provides one of the most reliable ways to date crustal rocks.”

This particular zircon, a tiny gem just 0.0157 inches long, was discovered in 2001, says the Guardian. But researchers have been combing the Jack Hills since the 1980s. Previous research on this and other Jack Hills zircons have pegged them to around 4.4 billion years old—uncertainties related to the dating technique make the exact ages unclear. The new research, published in Nature Geoscience, confirms the age of the zircon sample.

Different kinds of rocks form under different kinds of conditions, so having a firm age on the Jack Hills zircons can help geologists and geochemists figure out how the Earth evolved. Since they were first discovered the Jack Hills zircons have been rewriting our understanding of the earliest days of the planet. According to Rebecca Lindsey writing for NASA,

The crystals appear to contradict the conventional notion that the first 500 million years of Earth’s history—the Hadean Eon—were a continuously violent and chaotic time, when endless volcanism and continual meteor bombardment kept a global magma ocean simmering across the surface of the newly formed planet.

Instead, the chemical make up of the Jack Hills crystals suggests that they formed in the presence of liquid water, likely even an ocean. These crystals provide evidence that even the very early Earth was cooler and wetter than scientists used to think. A gentler Hadean could have permitted life to evolve far earlier in the planet’s history than scientists originally supposed.

Firming up the ancient date of the zircon samples doubles down on the shorter period of planetary temper tantrums.

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About Colin Schultz
Colin Schultz

Colin Schultz is a freelance science writer and editor based in Toronto, Canada. He blogs for Smart News and contributes to the American Geophysical Union. He has a B.Sc. in physical science and philosophy, and a M.A. in journalism.

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