That’s not just a little kid question but a genuine scientific mystery. In the early days of earth’s existence, according to scientists, the planet was just too hot for there to be water. After things cooled down, there still would have been no water. Comets have been discovered that have water vapor, so the leading theory has been that comets bombarded the earth and gave us the oceans.
But now a study has found that comet water is, for the most part, very different from earth water. Another candidate now is asteroids. But it’s hard to imagine how many comets or asteroids–which may have some water, but not all that much–it would take to create earth’s vast oceans. [Read more...]