4 Billion-Year-Old Crystal Confirmed As Oldest Piece of Earth

A crystal about the size of a dust mite has been identified as part of Earth's earliest crust, from 4.4 billion years ago, scientists reported Sunday in the journal Nature Geoscience.

The ancient crystal, called a zircon, was found in 2001 in the Jack Hills area, north of Perth Australia.

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"This is the oldest and the best dated of all the crystals that have been reported," John Valley, lead study author and professor in the Department of Geoscience at the University of Wisconsin-Madison, told CNN.

Scientists say the crystal has taught them some valuable lessons about early Earth. The planet would have supported liquid water and perhaps life in its early stages because of the crystal's chemistry, particularly its ratio of oxygen isotopes.

"What we've learned is that the Earth cooled much more quickly that people had thought," Valley said. "The surface formed a crust much more quickly than people thought."

Valley and his scientist published their first paper on the grain of zircon in 2001, according to the Los Angeles Times. They used the uranium lead system, which measures how many uranium atoms in the rock decayed into lead, to determine the crystal's age of 4.4 billion years. 

In their latest research published Sunday in Nature Geoscience, the scientists said they used a new method called atom-probe tomography that let them see individual atoms of lead in the sample to determine whether they had moved. They found, according to the Los Angeles Times, that the lead atoms do move around over time, but at such a small scale that it would not have interfered with the aging process.

"There have been challenges, because nothing in science goes without being questioned. It always has to be proven," Valley told National Public Radio. 

Valley said that crystals formed tens of millions of years after an early proto-Earth melted in a violent impact with a Mars-sized object, at about the time the moon was created.

"It would have glowed almost like a star," Valley said. "Nothing could exist on the surface. There would be no continental land masses. There'd be no liquid water. And there certainly would have been no life at that time."

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