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Why did the Earth produce life, when our celestial neighbours did not?
Wednesdays 9.00-9.30pm 19 February to 5 March 2003

This series of programmes looks at the oldest surviving remnants of the Earth – a strip of ancient seafloor now exposed near the Greenland icecap, the oldest piece of continent, now to be found in Western Australia, even a single grain of rock that appears to have survived from 4.4 billion years ago, holding evidence that oceans existed even then. The series includes the oldest evidence of life on Earth, the oldest fossils, even the traces of ancient raindrops that have survived over the eons.

See more images in the Picture Gallery and listen to Extended Interviews from the series.

Simon Wilde with Gabrielle Walker
Gabrielle Walker interviews geologist Simon Wilde at the place in Australia where the oldest surviving relic of the Earth was found - in the big rock they're sitting on.

Life, Moon – two words that seem to have little to do with one another. But the creation of the Moon, in a cataclysmic collision nearly 4.5thousand million years ago was an essential precondition for life to arise. The steady 24-hourly rotation of the Earth on its axis is a direct result of that collision and is responsible for the clement climate we have. Neighbouring Venus, which turns once in only 221 days, burns on its Sunwards face, and experiences eternal raging winds in its acid atmosphere. But the Earth was struck when it was still young by a stray protoplanet (“Theia” according to some researchers), creating our Moon in a matter of years and spinning us up on our axis. The Moon, raising tides in our ocean, and stabilising the Earth’s movements has played a key if remote part in the history of life on this planet.

That moon-forming impact also melted the Earth down to 1,000 km depth, creating a global magma ocean that would have glowed like a furnace. But a recent chance discovery has revealed that within 50 million years (an eternity for humanity, but a blink of the eye on these timescales) the first solid crust had formed on the Earth, and may even have resembled the rocks that today make our continents. That knowledge – and the suggestion that oceans of water had also formed by this time - rests on a single grain of resistant mineral too small to see with the naked eye, found in a non-descript rock in Western Australia.

Listen again Listen again to Programme 1

Roger Buick
Roger Buick describing the Australian landscape of 3.5 billion years ago.

In the second programme, Gabrielle Walker looks for the earliest traces of the Earth's surface - an improbable task as the oldest rocks have been buried under kilometres of younger ones - squeezed, cooked and twisted by powerful geological forces. But in Greenland, Gabrielle sees a thin sliver of ancient sea floor, complete with traces of volcanic lavas that have somehow survived, along with the evidence of water, and also indications that the first continents had already formed three thousand eight hundred million years ago.

Listen again Listen again to Programme 2

Minik Rosing with Gabrielle Walker
Native greenlander, Minik Rosing shows Gabrielle the rocks he discovered which contain the oldest traces of life - c.3.8 billion years ago.

The view that the early Earth was a barren wasteland is probably wrong. In the final programme Gabrielle Walker sees evidence that life thrived as far back as geology can take us. She also hears that the Earth was fashioned by life itself, as the first organisms created their own environment.

Listen again Listen again to Programme 3
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