An Ancient Oxygen Oasis: How the Earliest of Life Survived

Experts have found evidence of ancient pools of water untouched since Earth's earliest years. These primordial oases could provide researchers clues about our planet's earliest forms of life, serving as windows for peering into the dawn of creation.

It is believed that during the first half of Earth's existence, the air was devoid of any oxygen. Worse still, most of the planet's oceans consisted of little more than waves of toxic sludge, ash and metals. In fact, common knowledge of the Earth's formation asserts that oxygen didn't even flood calming oceans until 2.4 billion years ago.

However, researchers now suspect that the first biological production of oxygen began long before that. Incredibly, ancient rocks dating up to 4 billion years ago have often been found boasting bands of iron-rich minerals - minerals that can only form after oxygen interacts with dissolved iron the primordial ocean.

The source of this oxygen, then, was suspected to be the earliest of bacteria, pumping out oxygen from isolated pockets of cleaner water.

"The idea of oxygen oases in ancient seas has been around for a long time, but no one was able to pinpoint a specific example of such an oasis," Robert Riding at the University of Tennessee in Knoxville told NewScientist.

That's precisely why Riding is so excited about what his team has found. Collecting and analyzing rock samples from Steep Rock Lake in Ontario, Canada, Riding believes they have unearthed enough evidence to indicate that the ancient limestone formation has not changed since it was laid down billions of years ago.

The area was once "a shallow shelf, partly isolated from the open sea by a stromatolite reef, and close to a land mass that could have supplied nutrients," he said.

He adds that for limestone to form, calcium carbonate must be in water and stripped of its dissolved iron. Only oxygen-pumping bacteria could get that job done.

A study detailing this discovery in full was published in the journal Precambrian Research.