Mars Two Moons

How Much Water Is There On Earth? Magellan Would Be Shocked

It's good to be wet. Compared to our neighbors — Mars, Venus, the dust-dry Moon — we look the wettest. More than two thirds of our surface is ocean. Another twentieth is ice. Water, water, everywhere. We've got so much of it.

Or do we?

There's an oceanographer in Hawaii, Mike Mottl by name, who's been measuring — or trying to measure — how much water we have on this planet, and his calculations are a little startling. When you stand on the shore of Lake Michigan, or the Pacific, the water supply looks impressive. But Mike changes perspective; he steps off the planet and considers the whole sphere, the surface, the crust, the mantle, the core and he asks, how much total water is there? Is Earth carrying a lot? Or a little?

So he starts counting. First, of course, are our oceans. On a map there are five big ones, but combines them into one "global ocean."

In the upper mantle, or crust, there is water hiding in the tiny pores of certain "hydrous" minerals — in clay, in mica — and when conditions are right, that water can be squeezed out. When volcanoes erupt and you see a white billowing cloud hurtling to the sky, much of that is water vapor. Volcanoes belch water. How much is down there? Estimates vary (a lot) but Mottl figures there's maybe a fifth of a global ocean in the upper mantle.

In the lower, bigger mantle, the calculations get more theoretical, and therefore chancy, but he guesses anywhere from one tenth to 1.8 global oceans.

Then, all the way down, in the earth's core, nobody knows. There's enough capacity to house 60 oceans. Or maybe 100. The core could be very, very rich in hydrogen (a water ingredient) or totally dry. We have no data. Which leaves us in the odd position of not knowing where most of the Earth's water is. As Professor Mottl wrote me,

So I asked him: "If you had to make a rough calculation, right now, and no one's going to hold you to it, how much water do you think we have on earth?" And he said a conservative (albeit blind) guess would be the earth today carries with it 3 global oceans of water, 1/3 on top, where we can swim in it, sail on it, drink it, get rained on by it, and 2/3rds down below where it sits silently with the minerals.

Three global oceans of water! Sounds like a lot, no?

But from Mike's point of view, when you consider the mass of the earth, three oceans would take up less than one tenth of one percent of the planet. Think of your car. One tenth of one percent of your car would be smaller than a paper cup. (Well, it depends on the car, but you get the idea.) 0.1% is a tiny fraction.

mars two moons = HOAX

Yeah, it's not true. Don't stay up to take photos and be disappointed. It was in 2003 Aug 27th, when magnified 75 times, mars would appear as large and bright as the moon. But don't take my word for it ... afterall, you can't believe everything you read in an email. Take NASA's word for it, or how about Space.com, Sky and Telescope Magazine, Florida Stars, Snopes, About.com, or National Geographic?

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