Earth, 4bn years ago: balmy and pleasant

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The Independent Online

The first half billion years of our planet were long believed to be a hellish mix of fiery eruptions, swirling lava and incessant meteorites.

The first half billion years of our planet were long believed to be a hellish mix of fiery eruptions, swirling lava and incessant meteorites.

Not so. They were in fact balmy and pleasant, with cool oceans, blue skies and the same amount of landmass as today, according to new scientific research published yesterday.

The era from 4.5 billion to 4 billion years ago, traditionally the "Hadean Eon", or hellish time, will now need a new name after a four-year study turned up evidence that the Earth was hospitable enough to nurture life nearly from day one.

Geologists from the Australian National University in Canberra examined "tiny zircons" - crystals no wider than a human hair - in ancient rocks to find the temperature at which they crystallised. They were astonished to find that the average temperatures at which the early rocks formed were so low that a lot of water had to be present.

Geologist Professor Mark Harrison of the Australian National University, said: "We are essentially radically re-interpreting the earliest history of the Earth.What we've discovered is that the Earth was in fact a much more benign place."

Dr Harrison believes that within 200 million years of the solar system's formation the Earth could sustain life. "All researchers agree that life could not have emerged until there was liquid water at or near the Earth's surface. Thus the Earth may have harboured life for as much as 700 million years longer than currently believed."

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