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In the new Space.com article 7 billion-year-old stardust is oldest material found on Earth I had read about some pre-solar grains dating back to 7 billion years. What techniques are used in calculating age of these grains?

Are they collected first and then radiocarbon-dating is applied? If not, what other techniques might have been used?

Scientists recently identified the oldest material on Earth: stardust that's 7 billion years old, tucked away in a massive, rocky meteorite that struck our planet half a century ago.

This ancient interstellar dust, made of presolar grains (dust grains that predate our sun), was belched into the universe by dying stars during the final stages of their lives. Some of that dust eventually hitched a ride to Earth on an asteroid that produced the Murchison meteorite, a massive, 220-lb. (100 kilograms) rock that fell on Sept. 28, 1969, near Murchison, Victoria, in Australia.

New analysis of dozens of presolar grains from the Murchison meteorite revealed a range of ages, from about 4 million years older than our sun — which formed 4.6 billion years ago — up to 3 billion years older than our sun, researchers reported in a new study.

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  • $\begingroup$ Carbon-14 dating works on Earth because it is produced from nitrogen-14 in Earth's atmosphere and then absorbed by plants. I adjusted the format of your question to better fit the site's style. $\endgroup$ – uhoh Jan 13 at 23:00
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    $\begingroup$ @JamesK found it! See also telegraph.co.uk/science/2020/01/13/… and the PNAS article link therein, and bbc.com/news/science-environment-51099609 $\endgroup$ – uhoh Jan 13 at 23:21
  • $\begingroup$ space.com/stardust-oldest-material-on-earth.html $\endgroup$ – Pranay Jan 14 at 4:43
  • $\begingroup$ The space.com and bbc science journalists seem to however not have read the original paper in PNAS: "This age distribution is also consistent with the hypothesis that these grains originate from stars that initially formed during an enhanced SFR ∼7 Ga ago and became dust-producing AGB stars between ∼4.9 and ∼4.6 Ga ago." Hence, none of the dust found is so extremely old. Their fig. 4 is also showing ages of less than a Gyr. $\endgroup$ – AtmosphericPrisonEscape Jan 14 at 13:11
  • $\begingroup$ I saw somewhere that somebody pointed out that atom in the Solar system that isn't hydrogen or helium (or in the sun) was probably created about the same length of time ago as this dust. That sounds reasonable to me... $\endgroup$ – simon at rcl Jan 15 at 14:01
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The BBC article pointed out by @uhoh in a comment answers the question nicely.

To work out how old the grains were, the researchers measured how long they had been exposed to cosmic rays in space. These rays are high-energy particles that travel through our galaxy and penetrate solid matter.

Some of these rays interact with the matter they encounter and form new elements. The longer they are exposed, the more of these elements form. The researchers used a particular form (isotope) of the element neon - Ne-21 - to date the grains.

"I compare this with putting out a bucket in a rainstorm. Assuming the rainfall is constant, the amount of water that accumulates in the bucket tells you how long it was exposed," said Dr Heck.

Measuring how many of the new elements are present tells scientists how long the grain was exposed to cosmic rays. This in turn informs them how old it is.

Some of the pre-solar grains turned out to be the oldest ever discovered.

Based on how many cosmic rays had interacted with the grains, most had to be 4.6-4.9 billion years old. For comparison, the Sun is 4.6 billion years old and the Earth is 4.5 billion.

However, the oldest yielded a date of around 7.5 billion years old.

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