Starship Asterisk*

All the Water on Planet Earth

Explanation: How much of planet Earth is made of water? Very little, actually. Although oceans of water cover about 70 percent of Earth's surface, these oceans are shallow compared to the Earth's radius. The featured illustration shows what would happen if all of the water on or near the surface of the Earth were bunched up into a ball. The radius of this ball would be only about 700 kilometers, less than half the radius of the Earth's Moon, but slightly larger than Saturn's moon Rhea which, like many moons in our outer Solar System, is mostly water ice. How even this much water came to be on the Earth and whether any significant amount is trapped far beneath Earth's surface remain topics of research.

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It's interesting that there could be ten times more water than this stored in the mantle in the form of hydrated minerals (and almost certainly two to three times more).

In any case, it is interesting that the Earth has so relatively little water, certainly compared with the icy moons and ice giant planets of the outer solar system.

But unlike the icy moons and ice giant planets, the Earth keeps its water - its liquid water - on its own surface. That makes the Earth totally different from any other planetary body in the solar system.

Seeing that the presence of liquid surface water makes the Earth so different from anything else in the solar system, I have to wonder how many "true Earth analogs" - planets with liquid water on their surfaces, plus at least some land, too - really exist out there.

Ann

It is always joyfully sobering to reflect that everything we know, every life form that has ever existed, all we experience, our poetry and our wisdom, our loss and our horrors, all genius and all imagination. every hero and very villain occurs in a coat of paint on grapefruit ...

For comparison, what if all the planet's carbon was compressed into a single diamond: https://www.flickr.com/photos/rwfaves/7220975240/

This APOD is absurdist propaganda at best. The Earth is virtually a water world, particularly one that has a core and crust and one able to maintain protective magnetic field. How much bigger would that stupid sphere have been if all the continents were covered? Viewed from the pacific, it is all water and all the continents fit into the pacific with room to spare! https://www.gfdl.noaa.gov/wp-content/up ... ll_att.png. I'm afraid to ask if all the Ice sheets, total precipitable water and cloud contents were included. And as suggested below new papers have sighted vast quantities of H2O in the mantle as ringwoodite that would at least equal all surface water and:

"The surface water we have now came from degassing of molten rock. It came from the original rock ingredients of Earth," Schmandt said. "How much water is still inside the Earth today relative to the surface?" - Brandon Schmandt, (Seismologist, University of New Mexico)

Scott W Bennett wrote:This APOD is absurdist propaganda at best. The Earth is virtually a water world, particularly one that has a core and crust and one able to maintain protective magnetic field.

The Earth is not a water world. Not even close. It is a rocky world. There are genuine water worlds in our Solar System- formed in different places and maybe by different mechanisms than the terrestrial worlds, where water is at most a small constituent.

How much bigger would that stupid sphere have been if all the continents were covered?

Doubling the amount of water would do that. That would increase the diameter of the sphere by 25%. Barely noticeable.

I'm afraid to ask if all the Ice sheets, total precipitable water and cloud contents were included.

Yes. All of those.

And as suggested below new papers have sighted vast quantities of H2O in the mantle as ringwoodite that would at least equal all surface water...

If we take the highest estimates for mantle water (which isn't strictly H₂O), it would approximately double the diameter of the sphere. Still not a "water world".

Water, water, every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink.

Many years ago, I had a theory about how the atmosphere and the water on planet Earth had managed to remain after the sun ignited and the stellar winds blew and cleared a wide circle around the sun. My theory is not really scientific, but I believe that it is true.

In the Bible I read about the firmaments. I realized that the firmament that was spoken of might well be a blanket of ice that surrounded the planet and acted as a shield. I believe that there are other examples of this in our own solar system as with Jupiter’s moons. As the sun warmed the planet, the firmament melted and filled the low places and formed the oceans.

I believe that the “seeds of life” were contained in the water. That is how such an abundance of life came to be on this little planet out here in space.

This image seems to have caused a couple of believers in non-sense to come out of the woodwork. What is there about the image that could do this? I think it's the dichotomy between what our senses tell us and actual measurable reality. Humans have a very strong tendency to argue in favour of what their senses tell them. Training in science shows us how to go beyond our senses, but if you've never received (or received poor) instruction in science, that's going to be difficult for you. Hence... "This APOD is absurdist propaganda at best". That poster needs to do some research, and then do his own calculations, asking along the way for help as needed. Only that way will he convince himself that the APOD image shows what we think is true, as opposed to what we suppose might be true. Thinking is the key, and successful thinking requires data and appropriate methodology.

As for "My theory is not really scientific, but I believe that it is true". That kind of thinking is what happens when a young mind is inculcated with religious views to the exclusion of scientific knowledge and techniques. Look up some scientific work on the early history of our planet, spaceaman. You'll see that "in the beginning" Earth would have been rather too warm to support your "blanket of ice". Much later, about 4 billion years later, the Earth may have been nearly frozen over -- a theory called Snowball Earth, which you can look up -- but that's not what you're talking about, is it?

Rob

Thanks for your posts, Chris and Rob.
Here you can see the reason why the Earth is not a water world. The Earth formed out of smaller rocky bodies on the warm side of the so called snow line in the early solar system.

In space, water can exist only as a gas, water vapor, or as a solid, ice. The Earth was formed in the part of the solar system where all the water was in the form of water vapor. The building blocks of the Earth were rocky boulders, not blocks of ice. But on the cold side of the snow line, blocks of ice and ice-covered boulders were indeed floating around, and they collided with each other and formed the icy moons and ice giant planets of the outer solar system.

The Earth was formed with very little water. In a way you can say that the Earth has "too much water" considering where it was formed, and that it must have received a generous helping of water from space, maybe delivered by ice-rich asteroids.

The fact that Earth has a lot of liquid water even though it was formed on the ice-less warm side of the snow line in the primordial solar system suggests that other Earth-like planets in other solar systems should perhaps also form on the warm side of the snow line and have water delivered to them afterwards.

Ann

Chris Peterson wrote:

Scott W Bennett wrote:
How much bigger would that stupid sphere have been if all the continents were covered?

Doubling the amount of water would do that.
That would increase the diameter of the sphere by 25%.

• If the object is to cover every mountain (i.e., Everest)
  then one would have to quadruple the amount of water.
  
  That would increase the diameter of the sphere by ~60%.

It would be also interesting to visualize the earth crust as a sphere in comparison to the fluid inner part an the hard earth's core.

Don't be fooled by the small size. You could actually down in that much water.

A comment slightly modified from one I made in an earlier APOD featuring this image:

There is a large amount of water on Earth, in relation to the habitable volume of Earth. What the APOD really shows is that the total volume of Earth is so much (~600 times) bigger than the habitable volume of Earth. If we make the simple assumption that all of the Earth's water (1386 million km³) is habitable and make the further (even simpler) assumption that the lowest 1 km of atmosphere above the whole Earth's surface (510 million km³) is habitable, then (ignoring the volume of any subterranean habitable space, which I've just lumped in with the somewhat arbitrary habitable atmospheric volume), all of the Earth's water represents 73% of the habitable volume of Earth. The remaining volume of Earth is not habitable, but I am glad it is there, as its vast mass gives we surface dwellers an acceleration due to gravity of about 10 metres per second per second, of which I, for one, am rather fond.

The fact is that sea levels are predicted to rise in the coming centuries, by amounts expected to cause all sorts of problems for humanity. This appears to be at odds with the notion that there isn't that much water on Earth. Change is good for life in general, but not necessarily for human life in this particular instance. If one considers only the habitable volume of Earth, it could be considered to be a "water world" of sorts.

Excellent picture! BTW, it would be also interesting to show a second ball in the picture showing the earth atmosphere in water equivalent....scary!
Cheers, Viktor

viktor@viktortec.com wrote:
Excellent picture! BTW, it would be also interesting to show a second ball in the picture showing the earth atmosphere in water equivalent....scary!

The average depth of the ocean is a couple of kilometers whereas the average depth of atmospheric water is a couple of precipitable centimeters... a factor of ~100,000 in volume or of ~45 in spherical radius.

how big would this sphere be if you take the volume of every inhabitant of the Earth and create a sphere representing this volume ?

ta152h0 wrote:how big would this sphere be if you take the volume of every inhabitant of the Earth and create a sphere representing this volume ?

All of humanity would fit in a volume of about one cubic kilometer. Smaller than a pixel in this image.

The internal temperature from metabolic heat would be high enough to initiate thermonuclear fusion.

Chris Peterson wrote:

ta152h0 wrote:how big would this sphere be if you take the volume of every inhabitant of the Earth and create a sphere representing this volume ?

All of humanity would fit in a volume of about one cubic kilometer. Smaller than a pixel in this image.

The internal temperature from metabolic heat would be high enough to initiate thermonuclear fusion.

I agree on the size, but the core metabolic heat would dissipate rather quickly, as everyone was crushed and/or suffocated to death. Lovely thought.

But how much volume does every living thing on Earth take up?

ta152h0 wrote:how big would this sphere be if you take the volume of every inhabitant of the Earth and create a sphere representing this volume ?

You could also take all the human inhabitants and relocate them to the Hawaiian islands with some room to spare

Nitpicker wrote:

Chris Peterson wrote:

ta152h0 wrote:how big would this sphere be if you take the volume of every inhabitant of the Earth and create a sphere representing this volume ?

All of humanity would fit in a volume of about one cubic kilometer. Smaller than a pixel in this image.

The internal temperature from metabolic heat would be high enough to initiate thermonuclear fusion.

I agree on the size, but the core metabolic heat would dissipate rather quickly, as everyone was crushed and/or suffocated to death. Lovely thought.

But how much volume does every living thing on Earth take up?

Undoubtedly some of the volume of water in this image is actually a living creature. How much extra water not included in the calculation is locked away in living processes?

Doubling the amount of water would do that. That would increase the diameter of the sphere by 25%. Barely noticeable.

Exactly and that is my point!!

If we take the highest estimates for mantle water (which isn't strictly H₂O), it would approximately double the diameter of the sphere. Still not a "water world".

Exactly! And again you make my point!

Talk about a way to totally miss the point! Our terrestrial world is blessed by liquid H2O. Drowning all the continents with water, then bundling all that into a sphere 25% larger (As you say) demonstrate what a stupid but sensational comparison this APOD is.

As far as terrestrial worlds go the Earth is as close to a "Water world" as we will probably ever find, that is capable of supporting terrestrial life - and I say this - because it demonstrably so! A life supporting "Water world" requires a core and a crust of a large enough diameter to generate an atmosphere protecting magnetic field. If you were going to build one, you would have to start here and then add water. And by necessity the ratio between the sizes of the two spheres will be roughly as you depict!

There have been times in the past when the whole surface of the earth was beneath frozen H2O.

It is just plain dumbed down anti-science to entertain the silly notion of the Earth's water bundled into a little ball. You may as well bundle the whole crust beyond the depth man has ever ventured and roll it into a ball, it is about as arbitrary, useful and misleading a comparison!

What may be more interesting to know is what average depth of water would occur everywhere if the entire surface of earth was quite flat and covered with all the water calculated here.

As a GAS, the atmosphere (on Earth) has more depth, considerably more....

Guest wrote:It is just plain dumbed down anti-science to entertain the silly notion of the Earth's water bundled into a little ball. You may as well bundle the whole crust beyond the depth man has ever ventured and roll it into a ball, it is about as arbitrary, useful and misleading a comparison!

Come on. It's a useful demonstration that puts our precious resources into perspective. From our viewpoint the Earth seems vast and immutable, but in reality it is finite and we can easily trash it up.

Whatever point you want to make is not the point this picture conveys.