What we don't know about planet earth's water
I found this interesting as an item that shows just how much we still don't know about planet earth.
water below the ocean
"In fact, we don't really know how much water there is on Earth," said Gary Egbert, an oceanographer at OSU and co-author of the paper. "There is some evidence that there is many times more water below the ocean floor than there is in all the oceans of the world combined. Our results may shed some light on this question."