Scientists have found evidence that more than 3 billion years ago, the Earth was covered by the global oceans and turned into a “water world,”media reported. They found some telling chemical signals in an ancient ocean crust that pointed to a planet that had no continent. If these findings are confirmed by future work, they will help researchers refine their theories about where the first single-celled organisms are, how they appear edified on Earth, and what other planets might be habitable.
“An early Earth without an emerging continent may resemble a ‘water world’, providing an important environmental constraint to the origin and evolution of life on Earth and the possibility of life elsewhere,” the scientists wrote in the journal Nature Geoscience. “They conducted an in-depth study of a 3.2 billion-year-old seafloor plate at a geological site in northwest Australia called Panorama.
By analyzing more than 100 sediment samples, scientists found that 3.2 billion years ago, oxygen with a molecular mass of 18 in the ocean was more common than oxygen with a molecular mass of 16, which is more common in modern oceans. The most likely explanation, they argue, is that there were no continents on Earth at the time, because when these continents formed, the clay they contained absorbed heavy oxygen isotopes in the ocean.
But that doesn’t mean the earth doesn’t have any land. Scientists suspect that small “microcontinents” can protrude from all parts of the ocean, but they don’t think there was an entire continent on Earth that is rich in soil today. (theguardian)