Scientists Discover Earliest Record of Earth's Ancient Atmosphere

Scientists are getting the earliest look yet at Earth's ancient atmosphere. Chemical analysis of some of the world's oldest rocks has revealed a record of our planet's atmosphere four billion years ago.

This latest study builds on work conducted in 2008. At that time, researchers found rocks along the Hudson Bay coast in northern Quebec that were deposited as many as 4.3 billion years ago, which is just a couple of hundred million years after Earth formed. In this case, the researchers took these rocks and used mass spectrometry to measure the amounts of different isotopes of sulfur within the rocks.

What did the researchers find? It turns out that the sulfur in the rocks had been cycled through Earth's early atmosphere. This, in turn, showed that the atmosphere at the time was extremely oxygen-poor compared to today, and may have had more methane and carbon dioxide.

That said, what's interesting is that the isotopic fingerprint of this atmospheric cycling looks very similar to fingerprints from rocks that are a billion to two billion years younger.

"These younger rocks contain signs of microbial life and there are a couple of possible interpretations of our results," said Boswell Wing, one of the researchers, in a news release. "One interpretation is that biology controlled the composition of the atmosphere on early Earth, with similar microbial biospheres producing the same atmospheric gases from Earth's infancy to adolescence. We can't rule out, however, the possibility that the biosphere was decoupled from the atmosphere. In this case geology could have been the major player in setting the composition of ancient air, with massive volcanic eruptions producing gases that recurrently swamped out weak biological gas production."

Currently, the researchers are trying to find out whether the evidence supports the "biological" or the "geological" hypothesis. That said, the current findings do show a bit more about our ancient Earth.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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