Today's News, Tomorrow's Lesson - February 27, 2014

A sheep ranch in a remote region of western Australia has yielded
one of the most remarkable scientific discoveries of recent times: tiny
crystals that are the oldest known materials formed on Earth. The find
could offer vital clues to the origin of life on the planet.

The zircon crystals, measuring just twice the diameter of a human
hair, were extracted in 2001 from sandstone rock that formed an ancient
beach three billion years ago.

A team of researchers used two different methods to date the
crystals and found that they date back some 4.4 billion years, just 100
million years after the planet was formed.

This period of Earth’s history is known as the Hadean eon. It was
named after Hades, the ancient Greek god of the underworld, because of
the hellish conditions that characterized the planet, including a
molten surface and frequent meteorite strikes.

But the researchers, writing in the journal Nature Geoscience, said
the discovery shows that Earth may have formed a continental crust much
earlier than was previously believed and therefore conditions might not
have been so harsh.

If this is true, and temperatures at the time were low enough, the
planet may have been able to sustain liquid water and possibly even
microscopic life much earlier than previously thought.

Geoscience professor John Valley of the University of
Wisconsin-Madison, who led the researchers, said: “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.”

Due to plate tectonics and weathering, very little of the Earth’s
early surface remains for scientists to study. The vast majority of
surface rocks are relatively young in geological terms, less than a few
hundred million years old.

For this reason, the tiny zircon crystals found in the Jack Hills
region are a vital clue to the mystery of Earth’s early history.