A hundred and fifty years ago, in "Journey to the Centre of the Earth", French science-fiction forerunner Jules Verne pictured a vast sea that lay deep under our planet's surface.
Today, that strange and haunting image has found an unexpected echo in a scientific paper.
Writing in the journal Nature, scientists on Wednesday said they had found an elusive mineral pointing to the existence of a vast reservoir deep in Earth's mantle, 400-600 kilometres (250-375 miles) beneath our feet.
"This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area," said Graham Pearson of Canada's University of Alberta, who led the research.
"That particular zone in the Earth, the transition zone, might have as much water as all the world's oceans put together."
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