How much of the earth is water?

If you said seven tenths or two thirds, you’re wrong.

Seven tenths of the earth’s surface area may be covered with water, but water accounts for less than a fiftieth of one percent of the planet’s mass.

The earth is big—it weighs about 6 million, billion, billion kilograms. Half of this is contained in the lower mantle, the massive semi molten layer that begins 410 miles below the crust. Even on the apparently watery crust, the mass of the land is forty times greater than that of the oceans.

A Japanese experiment reported in 2002 suggests that there may be five times as much water dissolved in the lower mantle than sloshing around the earth’s surface. Even if this is true, water still only accounts for 0.1% of the earth’s mass.