Meteorite Charts 3

The Oldest Meteorite Finds

Most meteorites weather away quite quickly in the oxidizing environment of the Earth, while some meteorites may literally be observed as they rust away. However, other meteorites fell at more fortuitous locations and were preserved until this day, such as in the blue-ice fields of Antarctica or in the hot deserts of Africa. Many desert chondrite finds have been preserved for as long as 40,000 years while some achondrites exhibit much longer terrestrial residence times. With a terrestrial age of about 500 ka (500,000 years) lunar meteorite Dhofar 025 from Oman is the current record holder for hot deserts, closely followed by lunar find Dhofar 908 with a terrestrial age of 360 ka, and the martian find Dhofar 019 with an age of 340 ka. There is even one non-desert find, the eucrite Rio Cuarto 001 from Argentina, with a terrestrial age of 410 ka - finds that show that the metal-poor achondrites have a much better expectancy in the terrestrial environment than chondrites. A few Antarctic meteorite finds are even older than the finds mentioned above, but they are all young compared to a number of finds that have been preserved in sediments, or other geologic strata conducive to preservation: the so-called "fossil meteorites".

Fossil Meteorite Charts

The oldest of these fossils is the meteorite of Österplana, Sweden, which was found in 1987 imbedded in some limestone. This limestone, which dated from Ordovician times, revealed to the scientists that the imbedded meteorite had fallen 480 million years ago! The meteorite of Österplana is even older than the Brunflo meteorite which previously held the record for the "oldest". Brunflo, which was also found in Swedish limestone in 1980, has a terrestrial age of about 460 million years. As with true fossils, most of the original meteoritic minerals in fossil meteorites have been replaced by terrestrial minerals leaving only the outer structure of the meteorite preserved. Although both meteorites have been classified as chondrites, only their
chondritic structure remains as evidence of their extraterrestrial origins.
The oldest intact meteorite is the Lake Murray iron. A single mass with a massive iron-shale was found in a gully in Oklahoma, USA, in 1933. The meteorite was imbedded in some Antler Sandstone dating from the Lower Cretaceous, suggesting that Lake Murray landed in a near shore, shallow sea, while these beds were being deposited about 120 million years ago! In addition, although the exterior of this meteorite has been heavily corroded, the nickel-iron core has remained unaltered. It literally fell in times when dinosaurs still ruled the Earth! For further information on fossil meteorites please visit the Fossil Meteorites Page, compiled by Channon Visscher. >> continue >>

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