Zircon discovery offers clues to Earths formation

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The Koyal Group Info Mag articles - A zircon crystal embedded in sandstone found on a sheep ranch in Australia is the oldest piece of the Earth\u2019s crust to be discovered, shedding new light on our planet\u2019s formation.

The zircon, described in the journal Nature Geoscience, is about 4.4 billion years old and much smaller than a single grain of rice. But the tiny crystal carries an outsize significance: It is evidence that by that point in its history, Earth had gone from a superheated ball of molten rock to a congealed surface eventually capable of supporting life.

\u201cOne of the main goals of the space program is to understand if there\u2019s life elsewhere in the universe,\u201d said John Valley, a University of Wisconsin professor who led the study, collaborating with scientists in Australia, Canada and Puerto Rico.

By studying how the conditions of life came together on our planet, scientists believe we will learn what to look for on other planets.

But the earliest rocks and first evidences of life have been subject to dispute over the years. Some scientists, for example, maintain that the earliest evidence of life is about 3.8 billion years old and found in Isua, Greenland.

Skeptics, however, note that no fossils were found in the Greenland rock. They point instead to 3.5 billion-year-old evidence of life found in rocks in Pilbara, Australia.

That\u2019s no small difference \u2014 300 million years.

The age of the zircon described by the Valley team, however, does not appear to be in dispute. The Valley team used a new technique called atom-probe tomography, which allowed them to confirm the accuracy of the crystal\u2019s age. The new instrument, made in Wisconsin, is so sensitive that researchers were able to identify the atomic number and mass of each atom in the sample.

\u201cI think they have shown unequivocally, beyond a shadow of a doubt, that this grain is that old,\u201d said Samuel Bowring, an expert in the early history of the Earth and a geology professor at the Massachusetts Institute of Technology. Bowring was not involved in the new study.

\u201cIt\u2019s only one grain, mind you,\u201d he added, \u201cbut it\u2019s very significant.\u201d

Jim Mattinson, a professor emeritus in the department of earth science at University of California, Santa Barbara, said zircons have been found previously that were about the same age

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