A look back at the “Boring Billion”

Peter Crockford, PhD’18, recently explored the impact that cyanobacteria had on Earth’s atmosphere more than a billion years ago.

Story by Shannon Palus

January 2019

The composition of a planet’s atmosphere is a product, in part, of the creatures that inhabit it, and a billion or so years ago, Planet Earth was dominated by stringy ocean-dwellers called cyanobacteria.

They took in carbon dioxide, and let off oxygen, like plants. What would the atmosphere under their reign have looked like? “It’s been an open question how big a footprint these guys have had,” says Peter Crockford, PhD’18, who made answering that question the focus of his doctoral studies.

Crockford has revealed a slice of ancient cyanobacteria history by examining a salt sample from Ontario, taken from an area that long ago was a lake. The sample had been produced as minerals interacted with the Earth’s atmosphere, leaving encoded clues as to how much oxygen the tiny creatures produced.

“There’s only a handful of deposits on Earth today that preserve these signals,” says Crockford.

He examined the oxygen content in a colleague’s lab by shooting lasers at the sample. It turns out that the cyanobacteria of a billion and a half years ago weren’t producing much compared to the cyanobacteria and other oxygen-producing organisms of today.

While that had been the prevailing notion among scientists about an era with the nickname the “Boring Billion,” Crockford’s analysis provides the first solid evidence, which may make for more accurate models of our planet’s past.

And understanding what our planet used to look like could, perhaps, offer important clues about what to look for in other planets in order to find signs of rudimentary alien life, explains Crockford. “The most alien environment we have access to is [the] deep history of the Earth.”

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