7 billion-year-old stardust is oldest material found on Earth

rod

Oct 22, 2019
738
143
560
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.

7 billion-year-old stardust is oldest material found on Earth : Read more
"The researchers used a dating technique that measured the grains' exposure to cosmic rays during their interstellar journey over billions of years."

The method of CRE ages goes back quite a way, I think back to Clair Patterson et al in mid-50s and others. Many meteorites with CRE ages show much younger ages too, <=1E+8 years old (NASA ADS service), also the Apollo lunar mission rocks had young CRE ages too. Mars has young CRE ages too, A Habitable Past for a Desert Planet?, Sky & Telescope 127(3):12, 2014, March 2014, ""Cumberland's 'exposure age' is comparatively young, only 50 to 100 million years..."

This is a *stunning* report here for the CRE age determination.
 

rod

Oct 22, 2019
738
143
560
I did some more digging into this report for the Murchison meteorite ages. The Murchison meteorite, like the Allende is critical in dating the age of the Sun and solar system. Apparently the presolar grains with CRE ages 5 billion years old or more are said to be derived from another generation of stars that formed in a *bumper crop* 7 billion years ago. The explanation for the various presolar grain ages, chondrules ages, and don't forget the radiometric age (melt-age) - looks like a complex history to reconcile the different ages found on the meteorite.

‘Meteorite contains the oldest material on Earth: 7-billion-year-old stardust’, https://phys.org/news/2020-01-meteorite-oldest-material-earth-billion-year-old.html

["The researchers 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. For context, our Sun is 4.6 billion years old, and the Earth is 4.5 billion...But the age of the presolar grains wasn't the end of the discovery. Since presolar grains are formed when a star dies, they can tell us about the history of stars. And 7 billion years ago, there was apparently a bumper crop of new stars forming-a sort of astral baby boom. "We have more young grains that we expected," says Heck. "Our hypothesis is that the majority of those grains, which are 4.9 to 4.6 billion years old, formed in an episode of enhanced star formation. There was a time before the start of the Solar System when more stars formed than normal.”]

Here is a 2017 report on Murchison meteorite CRE ages, 1-2 million years for some chondrules, some others 4-40 million years.

‘Cosmogenic He and Ne in chondrules from clastic matrix and a lithic clast of Murchison: No pre-irradiation by the early sun’, https://ui.adsabs.harvard.edu/abs/2017GeCoA.213..618R/abstract

["Whether or not some meteorites retain a record of irradiation by a large flux of energetic particles from the early sun in the form of excesses of cosmic-ray produced noble gases in individual crystals or single chondrules is a topic of ongoing debate. Here, we present He and Ne isotopic data for individual chondrules in Murchison, a chondritic regolith breccia of the CM group. We separated 27 chondrules from a clastic matrix portion and 26 chondrules from an adjacent single so-called "primary accretionary rock" (Metzler et al., 1992). All chondrules from the primary rock fragment are expected to share a common irradiation history, whereas chondrules from the clastic matrix were stirred in the regolith independently of each other. All "primary rock chondrules" and 23 of the "matrix chondrules" have very similar concentrations of cosmogenic 3He and 21Ne, corresponding to a cosmic-ray exposure age to galactic cosmic rays (GCR) of ∼1.3-1.9 Ma, in the range of Murchison's meteoroid exposure age..”] ["Considering pre-irradiation in a regolith (2π exposure), the pre-exposure times for these four chondrules are at least between some 4 and 40 Ma near the very surface of the parent body, and even longer if they were buried deeper in the regolith."]
 

ASK THE COMMUNITY

Latest posts