A new analysis suggests Earth may have been a water world three to four billion years ago with a global ocean large enough to have submerged Mount Everest. Scientists at Harvard University examined our planet's ancient mantle and found that in ages past it was four times hotter due to radioactivity, and would therefore not be able to hold the current amount of water. 'We find that water storage capacity in a hot, early mantle may have been smaller than the amount of water Earth's mantle currently holds, so the additional water in the mantle today would have resided on...