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'Mars once had sea larger than the Earth's Arctic Ocean'
Washington, March 6
Ancient Mars was likely to
have possessed a primitive ocean that held more water than the Earth's
Arctic Ocean, the US space agency NASA said.
"Perhaps about 4.3
billion years ago, Mars would have had enough water to cover the entire
surface in a liquid layer about 450 feet (137 metres) deep," Xinhua
reported on Thursday, citing a NASA statement.
"More likely, the
water would have formed an ocean occupying almost half of Mars' northern
hemisphere, in some regions reaching depths greater than a mile (1.6
kilometres)," it added.
In all, the red planet's early ocean
would have contained 20 million cubic kilometres of water, but since
then, 87 percent of that water has been lost to space.
The new
findings, published in the US journal Science, were based on six-year
observations of two slightly different forms of water in Mars'
atmosphere using the most powerful telescopes on Earth including the W.
M. Keck Observatory on Hawaii.
By comparing the ratio of "heavy"
water containing deuterium, a heavier form of hydrogen, with regular
water, scientists believed that Mars must have lost a volume of water
6.5 times larger than the amount trapped in the present polar caps.
An
early ocean on Mars containing the lost water would have covered 19
percent of the planet's surface, they said. By comparison, the Atlantic
Ocean occupies 17 percent of the Earth's surface.
Based on the
surface of Mars today, a likely location for this water would be in the
Northern Plains, which has long been considered a good candidate because
of the low-lying ground.
"With Mars losing that much water, the
planet was very likely wet for a longer period of time than was
previously thought, suggesting the planet might have been habitable for
longer," said author of the study Michael Mumma, a senior scientist at
NASA's Goddard Space Flight Center.