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Evidence of ancient ocean on Mars

US: U.S. researchers have found evidence that a vast ocean likely covered one-third of the surface of Mars some 3.5 billion years ago. Researchers at the University of Colorado at Boulder based their finding on analysis of water-related features including scores of delta deposits and thousands of river valleys to test for the occurrence of an ocean sustained by a global hydrosphere on early Mars. The researchers used GIS to map the Martian terrain and conclude the ocean likely would have covered about 36 percent of the planet and contained about 30 million cubic miles, or 124 million cubic kilometers, of water.

The amount of water in the ancient ocean would have formed the equivalent of an 1,800-foot, or 550-meter deep layer of water spread out over the entire planet. The volume of the ancient Mars ocean would have been about 10 times less than current volume of Earth’s oceans, according to the study.

The study provides further support for the idea of a sustained sea on the Red Planet during the Noachian era more than 3 billion years ago, said Gaetano Di Achille, lead author of the study. More than half of the 52 river delta deposits identified by the researchers in the new study — each of which was fed by numerous river valleys — likely marked the boundaries of the proposed ocean, since all were at about the same elevation, Di Achille said. Twenty-nine of the 52 deltas were connected either to the ancient Mars ocean or to the groundwater table of the ocean and to several large, adjacent lakes, he said. The average elevation of the deltas on the edges of the proposed ocean was remarkably consistent around the whole planet, said Di Achille.

In addition, the large, ancient lakes upslope from the ancient Mars ocean likely formed inside impact craters and would have been filled by the transport of groundwater between the lakes and the ancient sea, according to the researchers.

The researchers reported their finding in the June 13 issue of Nature Geoscience.

Source: Xinhuanet