Earth may have been covered by global ocean 3 bn yrs ago: Scientists

The findings could help understand how single-cell organisms first emerged on Earth, according to scientists  

By DTE Staff
Published: Wednesday 04 March 2020

Earth may have been covered by a global ocean that turned the planet into a “water world” more than three billion years ago, according to a study published in Nature Geoscience.

The findings could help scientists to better understand where and how single-cell organisms first emerged on Earth.

According to the paper, the origin and evolution of Earth’s biosphere were shaped by the physical and chemical histories of the oceans.

Marine chemical sediments and altered ocean crust preserve a geochemical record of these histories. That is, they hold clues about the seawater that covered Earth at that time.

The authors of the paper studied about 3.24-billion-year-old ocean crust in the Panorama district of Western Australia. They analysed data from over 100 rock samples and studied the type of oxygen the ocean carried into its crust.

The researchers, in particular, studied two isotopes of oxygen — Oxygen-16 and slightly heavier Oxygen-18. They found that seawater contained more atoms of Oxygen-18 when the crust was formed over three bn years ago.

According to scientists, land masses with clay-rich soil have the capacity to absorb heavier isotopes of oxygen. Excess Oxygen-18 found in the rocks led them to conclude that there may not have been enough land to absorb the isotope.

“An early Earth without emergent continents may have resembled a ‘water world’, providing an important environmental constraint on the origin and evolution of life on Earth, as well as its possible existence elsewhere,” the scientists wrote in the journal.

However, scientists noted that the findings did not imply that Earth was entirely landless at the time. They suspect some land may have come up from the ocean, but not like we witness today.

According to scientists, the findings are a one-of-a-kind opportunity to examine clues about the chemistry of ocean water from billions of years ago.

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