Airdate: Jan 17, 2000
Scientist: Melanie Stiassny
The water that's on Earth today came here as it developed, condensing out of the matter of the cosmos.
ambience: Running stream
It's one of our oldest and most precious resources. We know there's a fixed amount of it on our planet, but we don't really know its origins. I'm Jim Metzner, and this is the Pulse of the Planet, presented by DuPont.
Today some thoughts on the origins of water.
"There's a really big question is where does all the water on this planet come from?"
Melanie Stiassny is a curator of fishes at the American Museum of Natural History.
"And to answer that question we really have to go back to the origin of the solar system because all of the water that's on this planet today came to this planet as it developed, as the earth condensed out of the matter of the cosmos."
According to most scientists, the earth dates back to some 4.6 billion years ago, when chucks of matter flung into space began to condense into planets, held by gravity in orbit around the sun. Well it's thought that part of that mixture was water, contained within the rocky landscape of our young planet.
"Now, then the question becomes, well how did that water in the rocks ever come to the surface to become the oceans of our planet? It looks as if the balance of the evidence suggests it was a very cataclysmic event. The oceans just exploded onto the surface and they've been here ever since.
"So the oceans that we have today, the water that we have today is ancient. And that's all the water we have. There's really very little coming to us from the cosmos. The water we have on this planet today is the water that we had when the planet formed and that's it. That's what we've got."
We're happy to say that you can now hear Pulse of the Planet online in streaming audio at nationalgeographic.com
Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation. I'm Jim Metzner.