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Tuesday, February 6th 2007

Earth's Oldest…Thing


Is This The Oldest Object On The Face Of The Earth

On January 18, 2000 a meteorite crashed into Tagish Lake in Canada. The Univ. of Western Ontario page and Wikipedia provide some details.

After NASA scientists examined it, some are ready to claim the rock formed before the Sun and is the oldest known object on earth.

Using electron microscopy and isotope tests, the scientists looked at the chemical make-up of the grains and discovered they had unusual ratios of different forms of nitrogen and hydrogen. Ratios of the isotope nitrogen-15 to nitrogen-14 were nearly twice those on Earth, while the ratio of deuterium, a heavy form of hydrogen, to normal hydrogen, was between 2.5 and nine times higher than usual.

Reporting in the journal Science today, a team lead by Keiko Nakamura-Messenger and Michael Zolensky show the levels of the isotopes in the meteorite could only arise from chemical reactions taking place in an extremely cold climate, where temperatures were as low as -260C. Those conditions would only be found in remote molecular clouds before the formation of the solar system, or at the very edge of what is known as the protosolar disc that was later to coalesce into the celestial bodies of the solar system. “These little particles within the meteorite seem to predate everything else. We don’t know exactly how old they are, but they could be billions of years older than the rest of the meteorite,” said Dr Zolensky.

That would mean that…

[...] while the first light from the sun fell on the fledgling Earth, as the dinosaurs rose and died out and humans gained dominance, the meteorite was hurtling around the heavens on a billions-of-years-long journey destined to terminate with a thud in Yukon territory.

You can visit Science here.

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