NASA identifies oldest known meteor crater on Earth

WASHINGTON: An international team led by a NASA scientist identified the oldest known meteor crater in Australia, which lends more clues to the formation of the Earth.

The study, published Tuesday in the journal Nature Communications, showed that the Yarrabubba meteor crater in a remote part of western Australia was 2.229 billion years old.

The Earth is pocked with roughly 190 major meteor craters, yet scientists only know the age of just a few.

"It's 200 million years older than the previously oldest known crater, which was the over 200-kilometer Vredefort Dome crater in South Africa," said Timmons Erickson, a research scientist at NASA's Johnson Space Center.

The original size of the crater is believed to have been 70 kilometers across, though its remnant today is only 20 kilometers. It is so old that it doesn't look like the typical impact crater that would have a clearly visible rim and deep bowl, according to the researchers.

To date the crater, Erickson's team gathered rock samples that contain zircon and monazite. The two mineral crystals contain uranium and lead, the ratio of which can be measured to determine the age of rock.

The timing of Yarrabubba's impact coincides with the formation of some of Earth's earliest icecaps and glaciers, shortly after the emergence of oxygen in the atmosphere.

"The great thing about this project is it shows how we can determine the age of ancient, deeply eroded craters," said Erickson.