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Oldest Crystal on Earth
A tiny crystal, little thicker than two human hairs, is the oldest Earth material ever found and it may force a reappraisal of what our planet was like early in its history. The grain, technically known as a zircon, has been dated to be 100 million years older than any solid sample previously discovered. It casts doubt on the accepted state of the Earth over four billion years ago: a boiling ocean of molten magma, devoid of life. The new picture emerging is of a world cool enough to support water and continents, and possibly the first stirrings of life. Cool Earth Zircon is a durable crystal made of silicon, oxygen and zirconium, among other elements. The record-breaking sample was one of a dozen specimens extracted from the Jack Hills section of northwestern Australia. It was dated in two separate studies at 4.4 and 4.3 billion years old.
Accepted view Both research teams dated the zircon grains by analyzing their uranium isotopes - types of uranium atoms with different masses. Uranium decays into lead. By calculating the ratio of uranium to lead, they determined that a dozen of the grains in their possession were very old indeed. The zircon analysis also involved looking at the ratio of oxygen isotopes. This showed the crystals could only have originated in a wet, low-temperature environment. This does not fit in with the accepted view that shortly after the Earth formed 4.5 to 4.6 billion years ago, the planet was a ball of molten rock. Scientists had thought that it took several hundred million years for the Earth to cool enough for oceans to condense out of a thick atmosphere. Catastrophic impacts Evidence from the Moon also suggests that about 500-600 million years after formation, Earth was subjected to intense bombardment from meteoroids. An intriguing question the new research raises is whether or not life could have arisen so early in the Earth's history. Professor Valley said that the zircon analysis was consistent with the suggested idea that life began but was completely extinguished in catastrophic impacts that melted the Earth's surface. Both research papers are published in the journal Nature. Commenting on the work, Professor Alex Halliday, of the Swiss Federal Institute of Technology in Zurich, said: "It represents a significant advance in reconstructing Earth's Dark Ages." Forbidden Archaeology While the above may be relatively uncontroversial, the use of archaeological evidence is often not so innocent. Over the past two centuries, researchers have found bones and artefacts showing humans like us existed millions of years ago. But scientists have suppressed, ignored, or forgotten these pieces of evidence.
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