Published: Tue, January 14, 2020
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Stardust: Oldest material on earth found inside meteorite

Stardust: Oldest material on earth found inside meteorite

The meteorite was known to contain so-called presolar grains - minerals cast off by stars at the end of their lives - but it is only now that the age of the sample has been verified. "Some people think that the star formation rate of the galaxy is constant", Heck said.

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Recent observations from the European Space Agency's Gaia mission have revealed a possible trigger for the apparent increase in star formation. "But still, knowing that [some] of those grains are at least 300 million years older than anything in the solar system is ... confirming that they are indeed the oldest solids in the solar system".

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

Star dust forms in the material that is emitted by stars and carried by star winds and blown into interstellar space.

To date the material, the researchers used a unique technique to measure the effects of cosmic rays hitting the grains.

The dust particles tend to be each 2 to 30 microns (1 micrometer is a thousandth of a millimeter). They are from silicon carbide, the first mineral formed when a star cools.

Presolar grains are more abundant in what we would call these primitive meteorites, Professor Bland said.

Of the 40 grains the researchers examined, the most ancient, at 7 billion years old, are 2.5 billion years older than Earth. Our sun, by comparison, is 4.6 billion years old, and Earth is 4.5 billion years old.

Researchers said Monday that new techniques have allowed them to identify the oldest solid material ever found on earth. It beats the oldest rocks on Earth, which were previously considered the most ancient material: zircon crystals discovered in Australia in 2014.

Nonetheless, the oldest yielded a date of around 7.5 billion years dilapidated.

Previous studies have noted that similar presolar grains have ages ranging from 5 billion to 4.6 billion years old, but the upper age limit of this Murchison stardust takes the the cake. 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. Heck said about 70,000 meteorites are now known to science, and of those, "at most 5% of these contain presolar grains". According to the statement released by NASA on November 20, a team of scientists has been able to discover "bio-essential" sugars in the meteorites, which consists of other biologically important compounds.

But the Field Museum has the largest portion of the Murchison meteorite, a treasure trove of presolar grains that fell in Victoria, Australia, in 1969. Impossibly small size they are hard to understand.

"This is one of the most exciting studies I've worked on, "said cosmochemist Philipp Heck of the Field Museum of Natural History and the University of Chicago". Then the crushed meteorite gets dissolved with acid until only the presolar grains remain.

Researchers compared the process to burning down a haystack to find the needle.

The findings shed light on a debate over whether or not new stars form at a steady rate, or whether there are highs and lows in the number of new stars over time.

"Large" is a relative term in this case, considering that the entire mass of material analyzed in the new study is just 300 nanograms, or 300 billionths of a gram. The scientists suggested that seven billion years ago, there was apparently a bumper crop of new stars forming - a sort of astral baby boom.

The star dust represented time capsules in front of the solar system.

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