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Published on May 15, 2012
If you could pull all the water in the ocean, the atmosphere, and on top of or beneath the surface of Earth into a ball, it would measure only about 950 (1,500km) miles across. By comparison, the moon is 2,160 (3,475km) in diameter. Of this, only about 3 percent if freshwater, and of that only about two-thirds is in a form or a location that is easily accessible to humans. (Animation by Jack Cook, Woods Hole Oceanographic Institution)