
Ancient crystals might rewrite Earth's early history - jiten_bansal
https://www.washingtonpost.com/news/speaking-of-science/wp/2015/10/20/ancient-crystals-might-rewrite-earths-early-history/
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dang
[https://news.ycombinator.com/item?id=10415212](https://news.ycombinator.com/item?id=10415212)

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rubidium
PNAS Paper Abstract:

Evidence of life on Earth is manifestly preserved in the rock record. However,
the microfossil record only extends to ∼3.5 billion years (Ga), the
chemofossil record arguably to ∼3.8 Ga, and the rock record to 4.0 Ga.
Detrital zircons from Jack Hills, Western Australia range in age up to nearly
4.4 Ga. From a population of over 10,000 Jack Hills zircons, we identified one
>3.8-Ga zircon that contains primary graphite inclusions. Here, we report
carbon isotopic measurements on these inclusions in a concordant, 4.10 ±
0.01-Ga zircon. We interpret these inclusions as primary due to their
enclosure in a crack-free host as shown by transmission X-ray microscopy and
their crystal habit. Their δ^13 C_PDB of −24 ± 5‰ is consistent with a
biogenic origin and may be evidence that a terrestrial biosphere had emerged
by 4.1 Ga, or ∼300 My earlier than has been previously proposed.

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clavalle
That's good news for those of us that hope we find life outside of Earth.
Inhospitable, once again, is shown not to mean lifeless.

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ajuc
And bad news for those terrified by Drake's equation.

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guelo
I'm really confused why a fleck of crystalline carbon is considered a bio
marker.

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rubidium
From my read, its the ratio of carbon 12 to 13.

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mkaziz
I hate headlines with "might" in it. Let me know when you figure it out -
otherwise you're just littering my brain.

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dekhn
The actual paper is also fairly cautious. This is some pretty tricky stuff at
the edge of what is technically capable to conclude. They're basically sharing
their findings with the community to get feedback and criticism- and if they
survive the criticismthe terminology will get a bit stronger.

