Forget surfing, sandcastles, and sunsets as we know them. The Earth could one day be as dry as a bone and as desolate as Mars, scientists say.
Don't ditch your yacht just yet, however. You've got another billion years.
Geologists from the Tokyo Institute of Technology have found that the Earth's oceans are seeping into the planet's interior five times faster than they are being replenished.
The Japanese team, led by scientist Shigenori Maruyama, calculated that about 1.12 billion tons of water drains into the Earth's mantle each year, while just .23 billion tons moves in the opposite direction, according to an article published in the 11 September issue of New Scientist.
Maruyama believes that over time the planet's oceans will disappear altogether.
"The world's oceans will dry up within a billion years," Maruyama told New Scientist. "Earth's surface will look very much like the surface of Mars, where a similar process seems to have taken place."
While others have come to similar conclusions about the rate at which oceans are draining, some scientists find Maruyama's theory of an oceanless world a bit hard to swallow.
"It's a neat idea," said UC Berkeley geophysics professor Raymond Jeanloz. "But I'm not so enthusiastic about it because there no reason to expect that how much water comes in and how much flows out is constant as a function of time."
Just because more water leaks into the earth now doesn't mean that it's going to continue that way, said Jeanloz.
"More water is going down than coming out right now, but in the past we thought the opposite was true -- that more was coming out than going in. Maybe we've been in this situation many times in geologic history before," he said.
Geoscientists generally believe that a large reservoir of water lies about 250 miles below the surface of the Earth, in the zone between the upper and lower mantles.
Water flows to the mantle through areas where oceanic plates dive beneath continental plates, called subduction zones. The water returns to the Earth's surface via volcanic hotspots and oceanic ridges, where molten rock and gases are pushed up through the earth's crust.
Maruyama will present his findings at the December meeting of the American Geophysical Union in San Francisco. But for now, the jury is still out on his theory, Jeanloz said.
"The uncertainties are pretty big, even with the current rate of water coming out. It is a huge extrapolation, but an interesting hypothesis."
