A tiny blue crystal from Australia is helping scientists better understand how the earth evolved into a habitable blue planet.

Researchers from around the world, and lead by John Valley, a geoscience professor at the University of Wisconsin-Madison, have announced a fragment of zircon picked from an outcropping of rocks in Western Australia's Jack Hills region offers confirmation that Earth formed a crust at least 4.4 billion years ago --- a mere 160 million years after the our solar system took shape.

The new finding further demonstrates the period of time when the earth was covered by a churning ocean of molten rock actually came a tad earlier in its geologic history than originally believed.

But, beyond everything else, Valley and his colleagues are certain the blue-hued zircon procured from a cattle ranch Down Under is the oldest sample of the planet ever found.

The discovery has been announced in the Feb. 23 issue of the journal Nature Geoscience.

"This confirms our view of how the Earth cooled and became habitable," said Valley, a geochemist who specializes in the study of zircons, the oldest terrestrial materials known. His work has revealed details of how the crust formed during the earliest phases of the planet.

"This may also help us understand how other habitable planets would form," he said.

The study, said Valley, underscores the theory of a "cool early Earth," where temperatures were low enough to allow liquid water, oceans and a hydrosphere, not to mention a then-fresh crust, he said. "The study reinforces our conclusion that Earth had a hydrosphere before 4.3 billion years ago," and possibly the initial hints of life.

Researchers employed a new technique called atom-probe tomography, which provides a way to accurately establish the age and thermal history of a piece of zircon by determining the mass of individual lead atoms contained in a sample.

Valley said his group also measured oxygen isotope ratios, which give evidence of early homogenization and later cooling of earth materials.

 "The Earth was assembled from a lot of heterogeneous material from the solar system," Valley explained, noting that the planet experienced intense bombardment by meteors during its early years of formation.

It also apparently suffered a collision with an object roughly the size of Mars about 4.5 billion years ago "that formed our moon, and melted and homogenized the Earth. Our samples formed after the magma oceans cooled and prove that these events were very early," he said.