Ancient crystal questions Earth's history

Researchers worked at the University of Edinburgh

Scientists may have to rewrite theories on what the Earth was like four billion years ago - after new research by geochemists at Edinburgh University.

Until now, scientists had believed that the planet was a boiling ocean of magma.

But by studying minerals, the researchers have found that the Earth was cool enough to have had water, continents, and even to support life.

It is thought the findings could also change theories on how the moon was formed.

The revelations followed the examination of a crystal which is more than 100 million years older than any sample found before.

These results may indicate that the earth cooled faster than anyone though

Professor John Valley, University of Wisconsin-Madison

The tiny grain of the mineral zircon, which was found in western Australia, was dated at 4.4 billion years old.

Geochemists from the University of Edinburgh played a leading role in the discovery, which was reported in the journal Nature.

The analysis was conducted at the University of Edinburgh geophysics laboratory run by Professor Colin Graham.

Working with colleagues from the United States and Australia, they reached their conclusions after reading the chemical signature of the crystal.

Professor John Valley, from the University of Wisconsin-Madison, helped analyse the sample.

The crystals were found in Australia

He said: "This is an astounding thing to find for 4.4 billion years ago.

"At that time, the Earth's surface should have been a magma ocean.

"Conventional wisdom could not have predicted a low temperature environment.

"These results may indicate that the Earth cooled faster than anyone thought."

The accepted wisdom is that the Earth was a swirling ball of molten metal and rock after it first formed 4.5 to 4.6bn years ago.

Scientists had thought that it took several hundred million years for the Earth to cool enough for oceans to be formed.

The young planet was also bombarded by meteors for 500 or 600 million years after its formation.

It is believed that the moon was created when an object the size of Mars slammed into the Earth, blasting pieces of the planet into space.

The research could challenge some theories

However, the new evidence suggests that the moon may have formed earlier than was thought, or by a different process.

The research has also raised the question of whether life may have formed on Earth that early in the planet's history.

The earliest known biochemical evidence for life is currently estimated at 3.85 billion years ago.

"It may have been that life evolved and was completely extinguished in catastrophic meteorite-triggered extinction events well before that," said Professor Valley.

Until now, the oldest evidence for liquid water on earth came from a rock which was estimated to be 3.8 billion years old.