Was Earth a water world?
Our blue planet may have been a whole lot bluer some 3 billion years ago, devoid of continents and almost entirely covered by a global ocean. That’s the conclusion of a new study that examined an ancient chunk of ocean-bed crust that now sits on its side in the Australian outback. The researchers examined the levels of two different isotopes of oxygen that seawater carried into the slab: Oxygen-16 and the slightly heavier atom Oxygen-18. After studying more than 100 rock samples, they determined that seawater contained more Oxygen-18 when the crust was formed 3.2 billion years ago. Today, land masses across Earth soak up heavier oxygen isotopes from water and lock them in clay-rich soils. The scientists suspect that the ancient ocean crust contains higher levels of Oxygen-18 because there were no soil-covered continents to absorb it. Study co-author Boswell Wing, from University of Colorado, Boulder, tells CNN.com that “teeny micro-continents” that resembled the Galapagos Islands might have stuck out of this ancient ocean. “We just don’t think that there was global-scale formation of continental soils like we have today.”