Space Dust Is the Source of the Earth's Water

Water on earth comes in two forms. There's normal water, which we know love hydrogen and oxygen,. Then there's heavy water, which is duterium and oxygen. And uterium is just a heavy form of hydrogen with an extra neutront in its nucleus. We've had sample return missions from comets and that have sampled the water. But when you look at the water in those they don't match. The hypothesis is that the space dust is actually the source of the rest of the erth's water.