Scientists in Western Australia have found a piece of zircon that dates from 4.4 billion years ago. The tiny sliver is the “oldest piece of earth” ever found.
The scientists involved in the research wrote in Nature Geoscience that this piece of zircon formed in the crust of Earth shortly (geologically speaking) after the crust itself had formed.
Earth formed 4.5 billion years ago but was a molten ball of rock for the first part of its early history. Minerals like zircon couldn't form until the crust was formed, and life certainly couldn't exist. The planet was so inhabitable that geologist Preston Cloud coined the term "Hadean" to name the period after Hades, the Greek god of the underworld.
The tiny piece of zircon suggests that the Earth’s crust may have formed earlier than previously thought, possibly just 160 million years after the solar system itself formed.
Zircon is known as “the most reliable natural chronometer” available to look at early Earth history. It contains uranium, which allows scientists to date it relatively precisely. Scientists used two different dating techniques to verify that this sliver of Zircon is in fact only about 100 million years younger than the Earth itself.
John Valley of The University of Wisconsin says that suggests life could have formed earlier too, as "we have no evidence that life existed then. We have no evidence that it didn't, but there is no reason why life could not have existed on Earth 4.3 billion years ago."
The piece of zircon is only about 200 by 400 microns, or twice the diameter of a human hair. Scientists are used to examining pieces of zircon that small, especially from the area in Western Australia where it was found. The Jack Hills region is known for its exceptionally old zircon.