 The short answer to that is yes there was. It was a huge amount of water. Water is the made of hydrogen and oxygen. It's the most common molecule in our solar system as it's forming. And so there's plenty of water around. But when you aggregate to form a planet like Earth and bring all that stuff in, everything heats up, you're bombarding, all of this material goes molten and it dries out again. So you've got this quandary about what's actually going into the Earth. On top of that we think the inner solar system was really dry as well. And so the Earth itself was forming out of materials which actually didn't have that much water in it. So can we tag what's coming into our Earth in our earliest formation episodes and understand where that water was coming from? And the answer is yes we can. We can use the isotope abundances of oxygen in that water and also hydrogen, the deuterium hydrogen ratio, proton neutron equals deuterium versus just proton for hydrogen. We can look at oxygen isotopes, oxygen 16, 17 and 18. And we can look at the relative abundances of those. Now these abundances of isotopes change during chemical and physical processes. So we get fractionations in these isotopes. And we can look at those fractionations to see how evaporation and so forth works. On top of that the solar system works in a very strange way. It obeys those physical fractionation laws but there is also a fractionation according to abundance. And so we see oxygen 16 changing in abundance and it creates this big chemical signature which we think is inherited into the original solar system. The water we see on the surface of the Earth is very similar to asteroids. And so we've gone out to these asteroids and the Hayabusa mission has now sampled a carbonaceous chondrite. Those types of meteorites are regarded as bringing in water to the Earth all through history. And those carbonaceous chondrites are very important. They have water, they have organics, they're the sort of the building blocks of a habitable planet. So were all these icy bodies flying around into the Earth? Well probably we've had some recently but most of the water that those associated with those bodies, the comets would have melted before they got into the inner solar system and dried out. Our Earth doesn't have a big inventory of those. It's largely through the delivery of the carbonaceous chondrites that we're seeing water coming into Earth.