Oldest zircon from lunar rock suggests molten moon solidified 90 million years after creation

January 27th, 2009 - 12:55 pm ICT by ANI  

London, Jan 27 (ANI): Scientists have found the oldest known zircon on Earth from a lunar rock sample, dating back to 4.42 billion years, which has helped pinpoint the age at which the molten moon solidified as 90 million years after the impact that created it.

According to a report in New Scientist, a team of scientists recovered a speck of the mineral zircon, thats older than any yet found on Earth, from a rock sample brought back by Apollo 17 astronauts.

Lunar zircons were not studied at the time of the Apollo missions because the technology to date them did not exist, said geologist Clive Neal of the University of Notre Dame, Indiana. Its serendipitous to find this, and really emphasizes the (value) of sample returns, he added.

Until now, the zircon found in lunar rocks was between 3.90 and 4.35 billion years old, the same as the oldest zircon found on Earth.

But, many of these lunar grains came from low-lying areas on the moon, where the crust had been resurfaced after being melted by meteorite impacts.

The new sample, found by Alexander Nemchin at Curtin University of Technology in Perth, Australia, and colleagues, is 4.42 billion years old, and came from the lunar highlands.

That means it crystallized after the crust first solidified, within 100 million years of the moons formation.

The grain sets limits on the moons age, according to Dianne Taylor of the University of California, Los Angeles, who has studied similar samples.

The moon is thought to have formed from debris ejected by a giant impact between Earth and a smaller body between 10 and 100 million years after the formation of the solar system, 4.57 billion years ago.

According to Taylor, the lunar crust formed within 90 million years of the impact, which tallies well with the age of the zircon. (ANI)

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