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The Earth is often compared to a majestic xanh marble, especially by those privileged few who have gazed upon it from orbit. This is due khổng lồ the prevalence of water on the planet"s surface. While water itself is not blue, water gives off blue light upon reflection. For those of us confined to living on the surface, the fact that our world is mostly covered in water is a well known fact. But how much of our planet is made up of water, exactly? lượt thích most facts pertaining to our world, the answer is a little more complicated than you might think, & takes into account a number of different qualifications.Bạn sẽ xem: What if all the land on earth was ocean và all the ocean was land?

In simplest terms, water makes up about 71% of the Earth"s surface, while the other 29% consists of continents và islands.

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To break the numbers down, 96.5% of all the Earth"s water is contained within the oceans as salt water, while the remaining 3.5% is freshwater lakes và frozen water locked up in glaciers và the polar ice caps. Of that fresh water, almost all of it takes the khung of ice: 69% of it, khổng lồ be exact. If you could melt all that ice, and the Earth"s surface was perfectly smooth, the sea levels would rise lớn an altitude of 2.7 km.

Aside from the water that exists in ice form, there is also the staggering amount of water that exists beneath the Earth"s surface. If you were khổng lồ gather all the Earth"s fresh water together as a single mass (as shown in the image above) it is estimated that it would measure some 1,386 million cubic kilometers (km3) in volume.


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Illustration showing all of Earth’s water, liquid fresh water, and water in lakes & rivers. Credit: Howard Perlman, USGS/illustraion by Jack Cook, WHOI

Meanwhile, the amount of water that exists as groundwater, rivers, lakes, & streams would constitute just over 10.6 million km3, which works out to lớn a little over 0.7%. Seen in this context, the limited and precious nature of freshwater becomes truly clear.

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The origin of water on the Earth"s surface, as well as the fact that it has more water than any other rocky planet in the Solar System, are two of long-standing mysteries concerning our planet.

Not that long ago, it was believed that our planet formed dry some 4.6 billion years ago, with high-energy impacts creating a molten surface on the infant Earth. According khổng lồ this theory, water was brought lớn the world"s oceans thanks khổng lồ icy comets, trans-Neptunian objects or water-rich meteoroids (protoplanets) from the outer reaches of the main asteroid belt colliding with the Earth.


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Many theories about the origins of water on Earth attribute it to collisions with comets và asteroids. Credit: NASA/JPL/Caltech

However, more recent research conducted by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts, has pushed the date of these origins back further. According lớn this new study, the world"s oceans also date back 4.6 billion years, when all the worlds of the inner Solar System were still forming.

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These meteorites are dated lớn the same epoch in which water was believed lớn have formed on Earth – some 11 million years after the formation of the Solar System. In short, it now appears that meteorites were depositing water on Earth in its earliest days.

While not ruling out the possibility that some of the water that covers 71 percent of Earth today may have arrived later, these findings suggest that there was enough already here for life khổng lồ have begun earlier than thought.