Oldest Material On Earth Has Been Just Discovered

Pablo Tucker
January 14, 2020

Ancient stardust extracted from a meteorite contains specks that are up to about 3 billion years older than the solar system, making them the oldest solids ever dated in a lab, researchers report.

"We've used this really old sample, the oldest solid samples available to science, to try to learn something about the history of our galaxy", said Philipp Heck, a meteorite expert at the Field Museum of Natural History in Chicago.

When stars die, particles formed within them are flung out into space.

This stardust is between between 5 billion and 7 billion years old - older than the sun and our solar system. In 1969, a great meteorite it fell to Earth, breaking into the atmosphere and throwing fragments of space rocks south of the city.

The presolar grains for the study were isolated from the Murchison meteorite about 30 years ago at the University of Chicago.

"It begins with crushing fragments of the meteorite down correct into a powder", acknowledged co-writer Jennika Greer, from the Self-discipline Museum and the College of Chicago. That's why the discovery of the presolar grains is such a rarity - only 5% of meteorites found on Earth contain them.

The exposure age data allowed researchers to measure their exposure to cosmic rays. The rate that cosmic rays hit the material, for example, and the number of times that those interactions split the silicon atoms need to be estimated. "And the longer they get exposed, the more those elements form", Heck said in the press release.

To know the age of grains, scientists quantify how long they had been exposed to cosmic rays in space.

The scientists learned that some of the presolar grains in their sample were the oldest ever discovered-based on how many cosmic rays they'd soaked up, most of the grains had to be 4.6 to 4.9 billion years old, and some grains were even older than 5.5 billion years.

The particles are termed presolar grains because they are older than the sun. Though it's uncertain what bound these grains, other studies have shown that some presolar grains are coated with a sticky film of organic matter, which could have cemented these clusters together, Heck said. But unlike dynamic planets, Murchison's parent asteroid is "an almost-inert piece of rock that formed from the solar nebula and hasn't changed since then", so the presolar grains haven't been cooked down into another type of mineral, Heck told Live Science. The new dating by this team confirms an astronomical theory which predicted a baby boom of stars before the formation of our sun, instead of a constant rhythm of star formation. "This is one of the key findings of our study", said Dr Heck. The oldest mineral entirely on Earth ended up being present in an Australian stone and ended up being 4.4 billion years of age, a hundred million years following the earth ended up being created. "There was a time before the solar system started when more stars formed than normal".

"Some people think that the star formation rate of the galaxy is constant", says Heck. "With this study, we have directly determined the lifetimes of stardust". A fallen grain, as part of our galactic history, is the closest thing to a sample return from a star. Stardust is the remnant material left behind after the death of a star in a supernova. "The awesome thing is we have a rock in our collection that we just take out of the cabinet and learn something about the history of our galaxy". "With stardust, we can trace that material back to the time before the sun".

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