APOD: All the Water on Planet Earth (2022 Sep 26)

[APOD Robot]

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. The next smallest ball depicts all of Earth's liquid fresh water, while the tiniest ball shows the volume of all of Earth's fresh-water lakes and rivers. How any of this 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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[MarkBour]

This beautiful graphic really surprises most people the first time they see it.
My reaction was: "Really, that's all? It seems an awfully small amount."

For Mars or the Moon, of course, there is water on both, but I don't know if
you could even see the liquid drop on an analogous graphic for them.

[Ann]

Earth is so wonderfully special because we have liquid water on our planet's surface. Not only that, but the amount of water is sufficiently small that the Earth's surface alternates between water and land.

This is particularly beneficial for life. Land-living species on Earth only exist where water is available. I'm too lazy to google today, but I have read that there is a desert in South America that is the world's driest place, and that is the only place on Earth where scientists have failed to find live.

Similarly, shallow water near land is ideal for many aquatic life forms. Life exists throughout the oceans, but nowhere is aquatic life more prevalent and richer in species than in shallow water near land.

Therefore, if there had been more water on Earth, and Earth had been a water world with no land, conditions would have been slightly less favorable for life. That is most certainly not to say that life couldn't have existed on such a world, of course.

But could we have existed?

Could we have built a technological civilization? Remember that under water you can't make fire. Could we have built great buildings and great machinery without fire?

And how would we have communicated? Would it have been possible to create languages nearly as intricate and rich as our spoken languages, if we couldn't speak the way we do now?

And how would we have stored knowledge? We couldn't have had libraries, books, computers. I don't know about you, but I'm not too optimistic about the possibilities of an entirely aquatic, highly communicative, great technological aquatic civilization. Remember, Atlantis died when it sank! (So it may never have existed... that's beside the point here.)

Would we have been mute mermaids, swimming in our water world in silence?

All the water on planet Earth. Illustration Credit: Jack Cook, Adam Nieman, Woods Hole Oceanographic Institution; Data source: Igor Shiklomanov.

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The illustration on the Pioneer plaque. Vectors by Oona Räisänen (Mysid); designed by Carl Sagan & Frank Drake; artwork by Linda Salzman Sagan - Vectorized in CorelDRAW from NASA image.

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This is our world. This is us. We live here because our world has just the right amount of readily available liquid water.

Ann

[Antony Rawlinson]

Can someone clarify why the ball representing "liquid fresh water" is so much larger than the one representing "all fresh-water lakes and rivers"?

I thought at first that the difference must be held up in Arctic and Antarctic ice, but it's telling us "liquid fresh water".

[Rauf]

Can someone clarify why the ball representing "liquid fresh water" is so much larger than the one representing "all fresh-water lakes and rivers"?

I thought at first that the difference must be held up in Arctic and Antarctic ice, but it's telling us "liquid fresh water".

Of all the available liquid fresh water on Earth, nearly all of it is Groundwater, which is water below Earth's surface. An smaller portion is water available in rivers and lakes.

[XgeoX]

Can someone clarify why the ball representing "liquid fresh water" is so much larger than the one representing "all fresh-water lakes and rivers"?

I thought at first that the difference must be held up in Arctic and Antarctic ice, but it's telling us "liquid fresh water".

Of all the available liquid fresh water on Earth, nearly all of it is Groundwater, which is water below Earth's surface. An smaller portion is water available in rivers and lakes.

There is as much water in the mantle as there is in all the oceans but I don’t know if it’s fresh or not.

[Chris Peterson]

Can someone clarify why the ball representing "liquid fresh water" is so much larger than the one representing "all fresh-water lakes and rivers"?

I thought at first that the difference must be held up in Arctic and Antarctic ice, but it's telling us "liquid fresh water".

Of all the available liquid fresh water on Earth, nearly all of it is Groundwater, which is water below Earth's surface. An smaller portion is water available in rivers and lakes.

There is as much water in the mantle as there is in all the oceans but I don’t know if it’s fresh or not.

There is good evidence of that, although it remains somewhat uncertain. The distinction of "fresh" is rather complex, as well, since most of this water is bound in odd ways to minerals. It's not like there's an aquifer of free water down there.

[Fred the Cat]

Let alone, all the people.

[bystander]

How Much Water is There on Earth?
USGS | Water Science School | 2019 Nov 13

[johnnydeep]

The radius of this ball would be only about 700 kilometers, less than half the radius of the Earth's Moon, but slightly larger smaller than Saturn's moon Rhea which, like many moons in our outer Solar System, is mostly water ice.

Earth's Moon - radius: 1737 km
Saturn's Moon Rhea - radius: 764 km
Total H2O ball - radius: 692 km

[beryllium732]

What would happen if we took Rhea and smashed it right into the Pacific Ocean? Or rather add it's water to Earth?

[Fred the Cat]

What would happen if we took Rhea and smashed it right into the Pacific Ocean? Or rather add it's water to Earth?

There are other choices.

[johnnydeep]

What would happen if we took Rhea and smashed it right into the Pacific Ocean? Or rather add it's water to Earth?

There are other choices.

Speaking of ocean worlds, I've often wondered whether there are any Earth-size or larger exoplanets whose mass consists almost entirely of water. I picture a Mars-size core enveloped by a planetary-wide ocean 4000+ miles deep! Not sure what would happen to the H2O near the core: would it merely be under extreme pressure, or would it be compressed into some other state or form?

[orin stepanek]

Water is man's best friend! Lets protect it and learn how to better harness it!

[Rauf]

Let alone, all the people.

I don't think all the water in all the humans would be that much.
If approximately humans are made of 30 liters of water, It means around 240,000,000,000 liters, which is just 240 million cubic meters. If I have done the calculations correctly, that means all of that water can be filled in a ball with just around 400 meters of radius. Not that big, I guess.

[johnnydeep]

Let alone, all the people.

I don't think all the water in all the humans would be that much.
If approximately humans are made of 30 liters of water, It means around 240,000,000,000 liters, which is just 240 million cubic meters. If I have done the calculations correctly, that means all of that water can be filled in a ball with just around 400 meters of radius. Not that big, I guess.

Your math (and assumptions) check out. Still pretty hard to believe though!

[XgeoX]

Let alone, all the people.

I don't think all the water in all the humans would be that much.
If approximately humans are made of 30 liters of water, It means around 240,000,000,000 liters, which is just 240 million cubic meters. If I have done the calculations correctly, that means all of that water can be filled in a ball with just around 400 meters of radius. Not that big, I guess.

Your math (and assumptions) check out. Still pretty hard to believe though!

I have a feeling if we took all the crap out of people the ball would be much bigger!

Eric

[Eclectic Man]

I wonder how much water is bound up in living things? After all, animals are basically bags of water with some impurities and plant sap contains a high proportion of water.

[TommiK]

I ask myself, what Radius would be if you put the Wohle mankind 8bn people in a Ball.

[VictorBorun]

I ask myself, what Radius would be if you put the Wohle mankind 8bn people in a Ball.

let a human be 50 kg of water, or 0.05 m³
Then 8 billion humans are 0.4 billion m³, or 0.4 km³
Now if a ball 3πR³/4 = 0.4 km³, then R = 0,55 km

[Chris Peterson]

I ask myself, what Radius would be if you put the Wohle mankind 8bn people in a Ball.
:)
:D

let a human be 50 kg of water, or 0.05 m³
Then 8 billion humans are 0.4 billion m³, or 0.4 km³
Now if a ball 3πR³/4 = 0.4 km³, then R = 0,55 km

Or looking at a more reasonable human volume of 0.15 m³, we get a total volume of about one cubic kilometer. Which, BTW, if packed with 8 billion humans would be (briefly) hot enough to sustain nuclear fusion.