Установите соответствие между текстами A–G и заголовками 1–8. Запишите свои ответы. Используйте каждую цифру только один раз. В задании один заголовок лишний.
1. The raw ingredients
2. Unlucky location
3. The cradle of life
4. Alien origin of Earth’s oceans
5. The great ocean conveyor
6. Unique planet
7. The keeper of our planet’s ecology
8. Colossal geological processes
A. Look at our blue planet from afar, and you could easily conclude that the Earth is nothing more than a world of water. Today, our oceans hold millions of life forms - from bacteria to blue whales. The water within drives the world’s winds, it temporarily becomes clouds or ice sheets at various locations, and it connects the poles via languorous deep-sea currents - processes that are all reflections of water’s singular role in absorbing and moving the Sun’s energy around our planet.
B. The oceans have not always existed on our planet. And the water within them is from outer space, arriving here many hundreds of millions of years after the Earth first took shape, 4.5 billion years ago. Back then, the surface of our planet was an unrecognisable hell - volcanic and bone dry. Our oceans’ water, the substance precious to every life form, arrived in frozen lumps from space during one of the most violent episodes in our planet’s early history.
C. Water is the second most common molecule in the universe and each one is made from two atoms of hydrogen and one of oxygen. The hydrogen comes from the moments after creation itself, the Big Bang. All of the hydrogen in the universe was made here and it remains the most common atom in the universe. The oxygen atoms came millions of years later. As the universe continued to expand, clouds of hydrogen clumped together and the atoms at the centre of the clouds began to fuse into helium.
D. Before the oceans could get to our planet, our planet had to form. Our early planet, 4.5 billion years ago, was a ferociously hot place. The surface was covered in volcanoes, much of the ground ran with molten magma, and huge rocks struck the surface on a regular basis. There is a reason why these first half billion years are known as the Hadean era, named for Hades, the hellish underworld of the ancient Greeks.
E. Venus is closer than the Earth to the Sun, and often cited as our evil twin, an example of how things might have turned out on our planet if everything had gone wrong. Its inability to hold onto oceans is a key example - the intense solar radiation on this planet would have created a humid world after the water had arrived in the Late Heavy Bombardment. Water vapour would have reached all the way to the highest reaches of the planet’s thick atmosphere.
F. Currently, Earth is the only known planet (or moon) to have consistent, stable bodies of liquid water on its surface. In our solar system, Earth orbits around the sun in an area called the habitable zone. The temperature, along with an ample amount of atmospheric pressure within this zone, allows water to be liquid for long periods of time. There is growing evidence suggesting that the planet Mars has subsurface liquid water, but this is yet to be confirmed.
G. Cold water has a higher density than warm water. Water gets colder with depth because cold, salty ocean water sinks to the bottom of the ocean basins. The sinking and transport of cold, salty water at depth combined with the wind-driven flow of warm water at the surface creates a complex pattern of ocean circulation. However, the ocean is not standing still. Currents and salinity are constantly replacing the bottom layer of ocean water with colder water.
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