How would an ocean planet be?

The world of the oceans

To this day, many secrets lie dormant in the depths of the oceans. Large parts of the world's oceans are still completely unexplored. We even know the moon better than the deep sea. But what we do know: Almost all of the water on earth - 97.5 percent to be precise - ripples in the five oceans.

The largest of all oceans is that Pacific. Its water surface measures a total of 180 million square kilometers! It makes up about half of all ocean areas. At the same time, the deepest point on earth is located in this ocean: it descends up to 11,034 meters into the Vitja Depth in the Mariana Trench, a deep-sea trench in the western Pacific.

The Atlantic is the second largest ocean. It was formed about 150 million years ago when the supercontinent Pangea broke up. With its 106 million square kilometers, it covers a fifth of the earth's surface.

The Indian ocean is mostly in the southern hemisphere. With an area of ​​almost 75 million square kilometers, it is a good deal smaller than the Atlantic and Pacific. Its deepest point is called Diamantina Depth, which is 8,047 below sea level.

The Southern Ocean is also called the Southern or Antarctic Ocean. It includes all marine areas south of the 60th parallel in the southern hemisphere. It is considered by seafarers to be the stormiest of all seas. The large tabular icebergs floating in its water are also typical of the Southern Ocean. They broke off the ice shelf that formed around the Antarctic continent.

That's all around the North Pole Arctic Oceanalso known as the Arctic Ocean. It is the smallest of the five oceans. About two thirds of the Arctic Ocean is covered with ice in winter. However, like the ice in the Southern Ocean, its ice cover continues to melt as a result of global warming.

Even if we live a few hundred kilometers away from them, oceans are very important to us. Their currents and the evaporation of sea water have an enormous influence on our weather. A large part of the air we breathe is also created in the world's oceans: algae that live here convert carbon dioxide into oxygen when exposed to sunlight.

The blue planet

Seen from space, the globe appears in a strong blue. This is because almost three quarters of the earth is covered with water. Small amounts of water are transparent, but from a certain depth onwards it becomes more and more blue. Because we see the mighty oceans blue, the earth is also called "the blue planet". The term south of the equator is particularly applicable. Because the southern hemisphere is almost completely covered by the sea, because a large part of the continents have migrated to the north due to plate movement.

The vast oceans contain almost all of the water on earth. There is a lot of salt dissolved in sea water, which is why it is not suitable as drinking water. The little fresh water on earth is frozen mainly in glaciers and ice caps. Only a tiny fraction of freshwater is found in groundwater, in lakes and rivers, or in the air.

But the view from the outside is deceptive: the earth's surface is largely covered by water, but measured by the diameter of the earth, the oceans are only a very thin layer. Therefore, the water makes up only a fraction of the earth's mass. For comparison: if the earth were the size of a basketball, all the water on earth would fit into a table tennis ball. And the drinking water would be proportionally even smaller than a single popcorn.

The water cycle

The water on earth is always on the move. Huge amounts of it are constantly moving - between sea, air and land - in an eternal cycle in which not a single drop is lost.

The motor of the water cycle is the sun: It heats the water of the seas, lakes and rivers so much that it evaporates. Plants also release water vapor into the atmosphere through tiny openings. The humid air rises, tiny water droplets gather in the air and form clouds. As rain, hail or snow, the water falls back into the sea or onto the earth. If it falls on the ground, it seeps into the ground, supplies plants or flows through the ground, over streams and rivers back into the sea. The eternal cycle of evaporation, precipitation and runoff starts all over again.

The water cycle has been around for almost as long as the earth has existed. He ensures that living beings on our planet are supplied with fresh water. And not only that: Without the water cycle, the weather as we know it would not exist.

How did the water come to earth?

About two thirds of the earth is covered with water - a unique selling point: the earth is the only planet in the solar system on which there is liquid water. Life originated in water, and water is also vital for us humans. But where does the water on earth actually come from?

Scientists suspect that the water comes from comets. These lumps of ice and dust originally formed on the edge of the solar system. But some also got into the interior of the solar system on orbits and became part of the newly emerging planets.

Initially, the young planets were very hot - so hot that the rock melted and formed a liquid ball. And the ice on the comets not only melted, it even evaporated. Because the water vapor was much lighter than the molten rock, it bubbled up towards the surface. There it escaped into the atmosphere through volcanoes.

As the earth slowly cooled, the steam turned back to liquid water. To put it more clearly: It started to rain. Those first downpours must have been stronger than any thunderstorm we can imagine today. And it must have rained for a very long time - tens of thousands of years. Large parts of the young earth's surface were flooded - in some places up to ten kilometers high. This is how the oceans came into being.

And what happened to the water on the other planets? Why are there no oceans there? Mercury doesn't have enough gravity to hold an atmosphere at all - like all gases, water vapor simply escaped into space. The same thing happened on the moon. On Venus, the solar radiation is so strong that the water has also evaporated into space. On the other hand, it is too cold on Mars, but large ice deposits are suspected there under the surface. And the gas planets have no solid surface on which seas could form. One suspects an ocean of water on Jupiter's moon Europa, but the surface is frozen. So the earth remains the only celestial body in the solar system with seas.

The ocean floor

The surface of the oceans glitters in a dark blue. It is hard to believe that the sea floor is sometimes many kilometers deeper and that a spectacular underwater landscape is hidden there below. Because the sea floor is not as smooth as the bottom of a swimming pool: On the sea floor there are high mountains, deep trenches and lava-spewing volcanoes as well as extensive plains.

The water in the oceans is not the same depth everywhere. The shallow shelf seas lie around the continents. Here the seabed slopes gently downwards from the coastline until it reaches a depth of around 200 meters below sea level. The bottom of the shelf seas consists of continental crust. Therefore it actually belongs to the mainland, even if it is washed over by sea water.

Only many kilometers away from the coast, on average after 74 kilometers, does the flat shelf area end with the shelf edge. From this edge it goes down steeply like a slide to a depth of about four kilometers. This steep slope forms the transition to the deep sea, into which no light can penetrate. That's why no plants grow down there. Only a few animal species were able to adapt to this habitat, despite the hostile conditions.

In the midst of the oceans rise mountains, the mid-ocean ridges. These underwater mountains stretch across the world's oceans for long stretches. In some places they protrude as islands above sea level. Iceland, for example, lies directly on the mid-Atlantic ridge, the longest mountain range in the world.

Deep trenches also crisscross the oceans. Most of them are in the Pacific. One of them is the Mariana Trench, the deepest trench in the world. It reaches down to 11,034 meters below sea level. Only two people have ever been down there: the oceanographer Jacques Piccard and his companion Don Walsh on their record dive in 1960.

What water can do

No matter whether we drink tap water, jump into a lake or are surprised by a rain shower - we are constantly in contact with water. And not only that: we are made up of water ourselves, around two thirds of which is actually water. Without question, water is part of our everyday life. But what seems completely normal to us has all kinds of peculiarities. And the water owes this primarily to its structure.

Everything that exists on this earth is made up of tiny building blocks, the atoms. This is also the case with pure water: It is a combination of two hydrogen atoms and one oxygen atom. These combine to form a water molecule, H for short2O. The individual water molecules are only loosely connected to one another.

This loose cohesion ensures that the connection between the molecules breaks at high temperatures: the water evaporates. If, on the other hand, it cools down significantly, the molecules organize themselves into a solid, regular grid, the ice. The special thing about it: In its solid form, water has a larger volume than in its liquid state.

The arrangement of the water molecules also ensures another property: the surface tension of the water. Because of this tension, water spiders and water striders can easily walk on a pond. But water can do even more: it is able to dissolve substances. Small grains of salt or sugar dissolve completely in water. Sea water, for example, contains large amounts of salt that we can taste but not see.

We owe the fact that lemons ripen on the island of Mainau on Lake Constance to another ability of water: it can store heat. Lakes or seas heat up in summer and keep the heat for a long time. That is why the temperatures on the coast fluctuate less than inland. Far from the coast, the temperature differences between day and night and between summer and winter are much greater than near the sea.

What are climate zones?

“In the morning it is changing to very cloudy with showers. In the afternoon the sun shows up at temperatures between 16 and 22 degrees ”, this is perhaps the weather report for southern Germany. The forecast is interesting for us because the weather is constantly changing. The situation is different with the climate, because that remains. Climate is the average weather in a region over a longer period of time. For example, the climate at the equator is hot and humid all year round. At the North Pole, on the other hand, the temperatures are icy and there is little precipitation. Between the equator and the poles there are again areas where, like us, things can be very changeable. But why is it that the climate on earth is so different?

The sun's radiation is not equally strong all over the world. How intensely it warms the earth depends on the angle of the sun's rays and thus on the latitude. Because the sun near the equator is almost vertical all year round, the earth is very heated here. In the direction of the poles, the rays of the sun strike at an increasingly flat angle: the same solar energy is distributed over an ever larger area. Therefore, the greater the distance from the equator, the cooler it becomes. This creates regions with different climates, the climatic zones.

According to the strength of the solar radiation, four different climate zones can be divided on the mainland of the earth: The tropics around the equator, the subtropics (from the Latin word “sub” for “under”) between the 23rd and 40th parallel, the moderate Zone of our latitudes and the polar regions around the north and south poles. Like belts, they draw these climatic zones around the earth in an east-west direction.

The climate does not only depend on the latitude, other influences also play a role. There is snow on Kilimanjaro, even though it is in the tropics. The fact that its summit is icy is due to the fact that the temperature drops with increasing altitude. The mountain climate is therefore always cooler than lower lying areas.

The distance to the sea also has an impact on the climate: water can store solar heat longer than the mainland. It is also warming up more slowly than the country. As a result, the sea water acts as a buffer for temperatures. The climate is therefore mild near the coast. In the interior of the country, this heat balance is missing and there is a continental climate in which the temperatures fluctuate much more than in the maritime climate near the sea.