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Earth has a diameter of 7,926 miles, it is almost, but not quite, a perfect sphere. Its equatorial radius is 6378 km, but its polar radius is 6357 km - in other words, the Earth is slightly flattened.

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About the Image

The crew of Apollo 17 took this photograph of Earth in December 1972 while their spacecraft was traveling between the Earth and the Moon. The orange-red deserts of Africa and Saudi Arabia stand in stark contrast to the deep blue of the oceans and the white of both clouds and snow-covered Antarctica.

Distance Information

The diameter of the Earth at the equator is 12,756 kilometers (km).

How Do We Calculate Distances of This Magnitude?

In 200 B.C., the size of the Earth was actually calculated to within 1% accuracy! Eratosthenes used Aristotle's idea that, if the Earth was round, distant stars in the night sky would appear at different positions to observers at different latitudes. Eratosthenes knew that on the first day of summer, the Sun passed directly overhead at Syene, Egypt. At midday of the same day, he measured the angular displacement of the Sun from overhead at the city of Alexandria - 5000 stadia away from Syene. He found that the angular displacement was 7.2 degrees - there are 360 degrees in a circle, making 7.2 degrees equivalent to 1/50 of a circle. Geometry tells us that the ratio of 1/50 is the same as the ratio of the distance between Syene and Alexandria to the total circumference of the Earth. Thus the circumference can be estimated by multiplying the distance between the two cities, 5000 stadia, by 50, equaling 250,000 stadia.

How do we convert to kilometers? Well, we believe that the unit of the "stadium" was about 0.15 km. This means that Eratosthenes estimated the circumference of the Earth to be about 40,000 km. He also knew that the circumference of a circle was equal to 2 times π (3.1415...) times the radius of the circle. (C = 2πr) With this information, Eratosthenes inferred that the Earth's radius was 6366 km. Both of these values are very close to the accepted modern values for the Earth's circumference and radius, 40,070 km and 6378 km respectively, which have since been measured by orbiting spacecraft.

The diameter of a circle is twice the radius, giving us a diameter for Earth of 12,756 km.

Note: The Earth is almost, but not quite, a perfect sphere. Its equatorial radius is 6378 km, but its polar radius is 6357 km - in other words, the Earth is slightly flattened. Eratosthenes was measuring the polar radius, and his value (using the 0.15 km/stadium conversion) lies between the polar and equatorial values.

Why Are These Distances Important To Astronomers?

Duringthe 18th and 19th centuries, astronomers used the diameter of the Earth as the basic yardstick in determining the size of the solar system. Today's astronomers usually do not need to know the size of the Earth for their daily research activities. Nevertheless, the diameter of the Earth still is the first step for us, the residents of this planet, in our attempt to understand the cosmic distance scale.

Travel Time

The Space Shuttle orbiter, with a velocity of 27,880 km per hour (17,322 miles per hour) takes approximately 90 minutes to orbit, or travel just outside the circumference of the Earth. At an altitude of 322 km (200 miles), an orbiter covers approximately 41,300 km (26,000 miles) in one orbit.

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This site is intended for students age 14 and up, and for anyone interested in learning about our universe.

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Astronauts and scientists have learned a lot about our planet by leaving it. From 240 miles (408 kilometers) away, aboard the International Space Station (ISS), astronauts are able to observe the thin, fragile atmosphere of Earth.

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Planet Earth: Facts About Its Orbit, Atmosphere & Size

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Earth is the only planet known to support life. Learn about what Earth is made of and where it came from.

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1. Reduce, reuse, and recycle

2. Volunteer

3. Educate

4. Conserve water

5. Choose sustainable

6. Shop wisely

7. Use long-lasting light bulbs

8. Plant a tree

9. Don't send chemicals into our waterways

10. Bike more

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national oceanic and atmospheric administration

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Ten simple choices for a healthier planet.

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The earth is made up of three different layers: the crust, the mantle, and the core.

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The structure of the earth is divided into four major components: the crust, the mantle, the outer core, and the inner core. Each layer has a unique chemical composition, physical state, and can impact life on Earth's surface. Movement in the mantle caused by variations in heat from the core, cause the plates to shift, which can cause earthquakes and volcanic eruptions. These natural hazards then change our landscape, and in some cases, threaten lives and property. Learn more about how the earth is constructed with these classroom resources.

Subjects

Earth Science, Geology, Geography, Physical Geography

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The structure of the earth is divided into four major components: the crust, the mantle, the outer core, and the inner core. Each layer has a unique chemical composition, physical state, and can impact life on Earth's surface. Movement in the mantle caused by variations in heat from the core, cause the plates to shift, which can cause earthquakes and volcanic eruptions.

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From space, Earth looks like the blue water world it is. About 70 percent of Earth’s surface is covered with water, and 97 percent of all that water is in the salty oceans. Only 3 percent of Earth’s water is freshwater — the water we drink.

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[/caption]Most of the Earth surface, about 70%, is covered with water. The remaining 30% is made up of the seven continental landmasses. Underneath the water that fills the oceans, and the dirt and plants that cover the continents, the Earth's surface layer is made of rock. This outer layer formed a hard, rocky crust as lava cooled about 4.5 billion years ago. This crust is broken into many large plates(tectonic plates) that move slowly relative to each other. The mountain ranges around the world formed when two plates collided and their edges are forced up. Many other surface features are the result of the movement of these tectonic plates. The plates move anywhere from 25 to 100 mm per year. About 250 million years ago most of the land was connected together.

The rocky layer under the soil of the Earth is called the crust. This comprises the continents and ocean basins. The crust has a variable thickness, being 35-70 km thick on the continents and 5-10 km thick in the ocean basins. The crust is composed mainly of alumino-silicates. The entire crust occupies just 1% of the Earth's volume. The temperature of the crust increases as you go deeper into the Earth. It starts out cool, but can get up to 400 degrees C at the boundary between the crust and the mantle.

The tectonic plates are actually floating on the molten asthenosphere which is the lower mantle of the Earth. Earthquakes, volcanoes, mountains, and oceanic trench formation occur along plate boundaries. The plates are in constant motion. The reason that tectonic plates are able to move is the Earth's lithosphere has a higher strength and lower density than the underlying asthenosphere. Their movement is dictated by heat dissipation from the Earth's mantle. Lateral density variations in the mantle result in convection, which is transferred into plate motion through some combination of frictional drag, downward suction at the subduction zones, and variations in topography and density of the crust that result in differences in gravitational forces.

The Earth's surface may seemed fixed and permanent to us, but underneath our feet there is constant motion and changes that we may not notice until there is an earthquake or a volcanic eruption. Here on Universe Today we have a great article with interesting facts about Earth. Astronomy Cast offers a good episode about plate tectonics. Here is the NASA webpage about Earth

References:
NASA Earth Observatory
NASA: Continents in Collision
NASA: Structure of the Earth

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caption]Most of the Earth surface, about 70%, is covered with water. The remaining 30% is made up of the seven continental landmasses. Underneath the water that fills the oceans, and the dirt and plants that cover the continents, the Earth's surface layer is made of rock.

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Mixture of gasses that becomes thinner as we move away from the planet toward space. Most of the atmosphere is nitrogen (78 percent), oxygen (21 percent), argon, and other gases (1 percent).

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One of the main components of Earth's interdependent physical systems is the atmosphere. An atmosphere is made of the layers of gases surrounding a planet or other celestial body. Earth's atmosphere is composed of about 78% nitrogen, 21% oxygen, and one percent other gases. These gases are found in atmospheric layers (troposphere, stratosphere, mesosphere, thermosphere, and exosphere) defined by unique features such as temperature and pressure. The atmosphere protects life on earth by shielding it from incoming ultraviolet (UV) radiation, keeping the planet warm through insulation, and preventing extremes between day and night temperatures. The sun heats layers of the atmosphere causing it to convect driving air movement and weather patterns around the world.

Subjects

Biology, Earth Science, Geology, Geography, Physical Geography

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One of the main components of Earth's interdependent physical systems is the atmosphere. An atmosphere is made of the layers of gases surrounding a planet or other celestial body. Earth's atmosphere is composed of about 78% nitrogen, 21% oxygen, and one percent other gases.

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Earth orbits the sun once every 365.25 days. Since our calendar years have only 365 days, we add an extra leap day every four years to account for the difference.

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Earth, our home planet, is a world unlike any other. The third planet from the sun, Earth is the only place in the known universe confirmed to host life.

With a radius of 3,959 miles, Earth is the fifth largest planet in our solar system, and it's the only one known for sure to have liquid water on its surface. Earth is also unique in terms of monikers. Every other solar system planet was named for a Greek or Roman deity, but for at least a thousand years, some cultures have described our world using the Germanic word "earth," which means simply "the ground."

Our dance around the sun

Earth orbits the sun once every 365.25 days. Since our calendar years have only 365 days, we add an extra leap day every four years to account for the difference.

Though we can't feel it, Earth zooms through its orbit at an average velocity of 18.5 miles a second. During this circuit, our planet is an average of 93 million miles away from the sun, a distance that takes light about eight minutes to traverse. Astronomers define this distance as one astronomical unit (AU), a measure that serves as a handy cosmic yardstick.

Earth rotates on its axis every 23.9 hours, defining day and night for surface dwellers. This axis of rotation is tilted 23.4 degrees away from the plane of Earth's orbit around the sun, giving us seasons. Whichever hemisphere is tilted closer to the sun experiences summer, while the hemisphere tilted away gets winter. In the spring and fall, each hemisphere receives similar amounts of light. On two specific dates each year-called the equinoxes-both hemispheres get illuminated equally.

Many layers, many features

About 4.5 billion years ago, gravity coaxed Earth to form from the gaseous, dusty disk that surrounded our young sun. Over time, Earth's interior-which is made mostly of silicate rocks and metals-differentiated into four layers.

At the planet's heart lies the inner core, a solid sphere of iron and nickel that's 759 miles wide and as hot as 9,800 degrees Fahrenheit. The inner core is surrounded by the outer core, a 1,400-mile-thick band of iron and nickel fluids. Beyond the outer core lies the mantle, a 1,800-mile-thick layer of viscous molten rock on which Earth's outermost layer, the crust, rests. On land, the continental crust is an average of 19 miles thick, but the oceanic crust that forms the seafloor is thinner-about three miles thick-and denser.

Like Venus and Mars, Earth has mountains, valleys, and volcanoes. But unlike its rocky siblings, almost 70 percent of Earth's surface is covered in oceans of liquid water that average 2.5 miles deep. These bodies of water contain 97 percent of Earth's volcanoes and the mid-ocean ridge, a massive mountain range more than 40,000 miles long.

Earth's crust and upper mantle are divided into massive plates that grind against each other in slow motion. As these plates collide, tear apart, or slide past each other, they give rise to our very active geology. Earthquakes rumble as these plates snag and slip past each other. Many volcanoes form as seafloor crust smashes into and slides beneath continental crust. When plates of continental crust collide, mountain ranges such as the Himalaya are pushed toward the skies.

Protective fields and gases

Earth's atmosphere is 78 percent nitrogen, 21 percent oxygen, and one percent other gases such as carbon dioxide, water vapor, and argon. Much like a greenhouse, this blanket of gases absorbs and retains heat. On average, Earth's surface temperature is about 57 degrees Fahrenheit; without our atmosphere, it'd be zero degrees. In the last two centuries, humans have added enough greenhouse gases to the atmosphere to raise Earth's average temperature by 1.8 degrees Fahrenheit. This extra heat has altered Earth's weather patterns in many ways.

The atmosphere not only nourishes life on Earth, but it also protects it: It's thick enough that many meteorites burn up before impact from friction, and its gases-such as ozone-block DNA-damaging ultraviolet light from reaching the surface. But for all that our atmosphere does, it's surprisingly thin. Ninety percent of Earth's atmosphere lies within just 10 miles of the planet's surface.

We also enjoy protection from Earth's magnetic field, generated by our planet's rotation and its iron-nickel core. This teardrop-shaped field shields Earth from high-energy particles launched at us from the sun and elsewhere in the cosmos. But due to the field's structure, some particles get funneled to Earth's Poles and collide with our atmosphere, yielding aurorae, the natural fireworks show known by some as the northern lights.

Spaceship Earth

Earth is the planet we have the best opportunity to understand in detail-helping us see how other rocky planets behave, even those orbiting distant stars. As a result, scientists are increasingly monitoring Earth from space. NASA alone has dozens of missions dedicated to solving our planet's mysteries.

At the same time, telescopes are gazing outward to find other Earths. Thanks to instruments such as NASA's Kepler Space Telescope, astronomers have found more than 3,800 planets orbiting other stars, some of which are about the size of Earth, and a handful of which orbit in the zones around their stars that are just the right temperature to be potentially habitable. Other missions, such as the Transiting Exoplanet Survey Satellite, are poised to find even more.

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Learn more about planet Earth and its role in the solar system.

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The Deepest Known Point in Earth’s Ocean

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The Deepest Known Point in Earth’s Ocean

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Over 36,000 feet (11,000 meters) deep in the Mariana Trench in the Pacific Ocean.

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Home " Records " Deepest Point in the Oceans

The Challenger Deep in the Mariana Trench is the deepest known location in Earth's oceans.

Measuring the Greatest Ocean Depth

The Challenger Deep in the Mariana Trench is the deepest known point in Earth's oceans. In 2010 the United States Center for Coastal & Ocean Mapping measured the depth of the Challenger Deep at 10,994 meters (36,070 feet) below sea level with an estimated vertical accuracy of ± 40 meters. If Mount Everest, the highest mountain on Earth, were placed at this location it would be covered by over one mile of water.

The first depth measurements in the Mariana Trench were made by the British survey ship HMS Challenger, which was used by the Royal Navy in 1875 to conduct research in the trench. The greatest depth that they recorded at that time was 8,184 meters (26,850 feet).

In 1951, another Royal Navy vessel, also named the "HMS Challenger," returned to the area for additional measurements. They discovered an even deeper location with a depth of 10,900 meters (35,760 feet) determined by echo sounding. The Challenger Deep was named after the Royal Navy vessel that made these measurements.

In 2009, sonar mapping done by researchers aboard the RV Kilo Moana, operated by the University of Hawaii, determined the depth to be 10,971 meters (35,994 feet) with a potential error of ± 22 meters. The most recent measurement, done in 2010, is the 10,994 meter ( ± 40 meter accuracy) depth reported at the top of this article, measured by the United States Center for Coastal & Ocean Mapping.

Exploring the Challenger Deep

The Challenger Deep was first explored by humans when Jacques Piccard and Don Walsh descended in the Trieste bathyscaphe in 1960. They reached a depth of 10,916 meters (35,814 feet).

In 2009 researchers from Woods Hole Oceanographic Institution completed the deepest dive by an unmanned robotic vehicle in the Challenger Deep. Their Nereus robotic vehicle reached a depth of 10,902 meters.

Why is the ocean so deep here?

The Mariana Trench is located at a convergent plate boundary. Here two converging plates of oceanic lithosphere collide with one another. At this collision point, one of the plates descends into the mantle. At the line of contact between the two plates, the downward flexure forms a trough known as an ocean trench. An example of an ocean trench is shown in the diagram. Ocean trenches form some of the deepest locations in Earth's oceans.

Earthquakes in the Mariana Trench

The Mariana Trench occurs along a plate boundary between the Philippine Plate and the Pacific Plate. The Pacific Plate is on the eastern and southern side of this boundary, and the Philippine Plate is on the western and northern side of this boundary.

Both of these plates are moving in a northwesterly direction, but the Pacific Plate is moving faster than the Philippine Plate. The motion of these plates produces a convergent plate boundary because the greater speed of the Pacific Plate is causing it to collide into the Philippine Plate. This collision produces a subduction zone at the Mariana Trench as the Pacific Plate descends into the mantle and under the Philippine Plate.

This collision occurs at variable speeds along the curving boundary of the plates, but the average relative motion is in the range of tens of millimeters per year. Recurrent earthquakes occur along this plate boundary because the Pacific Plate's descent into the mantle is not smooth and uniform. Instead, the plates are usually stuck with pressure accumulating, but with sudden slips as the plates move a few millimeters to a few meters at a time. When the plates slip, vibrations are produced, and those vibrations travel through Earth's crust as earthquake waves.

As the Pacific Plate descends into the mantle, it is heated by friction and the geothermal gradient. At a depth of approximately 100 miles, the rocks have been heated to a point where some minerals begin to melt. This melting produces magma that rises towards the surface because of its lower density. As the magma reaches the surface, volcanic eruptions are produced. These eruptions have formed the Mariana Island archipelago.

Find Other Topics on Geology.com:

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The Challenger Deep is the deepest known location in Earth's oceans. In 2010 its depth was measured at 10,994 meters below sea level with an accuracy of plus or minus 40 meters.

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The highest point on Earth’s surface is Mount Everest on the border of Nepal and China, at 29,035 feet (8,850 meters).

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(Image credit: Didier Marti via Getty Images)

It's no secret that Mount Everest, the jewel in Nepal's Himalayan crown, is the world's premier mountain. It's one of those facts embedded in childhood, like knowing that Neil Armstrong was the first person to walk on the or that blue whales are the largest animals ever to have lived.

You may be surprised to hear, then, that other peaks could conceivably be considered tallest; it just depends how you measure them.

So, judging by different parameters - including tallest by altitude, tallest from base to top and tallest based on being the farthest point from Earth's center - what is the tallest mountain in the world?

Mount Everest, located deep in the Mahālangūr Himāl subrange of the Himalayas, is undoubtedly the most famous - and alluring - of all our planet's mountains. Also known as Chomolungma, meaning "Goddess Mother of the World" in Tibetan, Everest was first scaled on May 29, 1953 by Tenzing Norgay, a Sherpa of Nepal, and New Zealander Edmund Hillary, and has since been successfully climbed by around 4,000 people. The mountain has also claimed the lives of over 300 since records started being kept in 1922, according to the Guardian.

Researchers have measured Mount Everest many times over the past few decades, but the latest assessment, announced in November 2021, puts it at 29,031.69 feet (8,848.86 meters) above sea level, which is almost 5.5 miles (8.8 kilometers) tall. It's a pretty impressive height, but it does raise a question: Why do we use "above sea level" when determining the world's tallest peak?

"In order to have comparability in measurements, it is necessary to have a consistent baseline," Martin Price, a professor and founding director of the Centre for Mountain Studies at the University of Highlands and Islands in Scotland, told Live Science.

"Historically, and even now, elevation is usually given as height above mean sea level," Price told Live Science in an email. "However, this has to be with reference to a standard mean sea level, which has to be defined. Sea levels are different in different parts of the world, and they're changing due to climate change."

As a result, "elevation is now measured in relation to the mathematically defined geoid of the Earth," he said. The geoid is, according to the National Oceanic and Atmospheric Administration, "a model of global mean sea level that is used to measure precise surface elevations." This average is used to ascertain the height of mountains, a process that sometimes requires an aeroplane to fly "back and forth over a mountain in a series of parallel lines to measure how much gravity pulls down on its peak," according to GIM International. These measurements, in conjunction with GPS readings, provide incredibly accurate elevation readings.

(Image credit: Westend61 via Getty Images)

So, all mountains are measured from sea level, predominantly for convenience and consistency, but what if measurements were simply taken from base to peak? Would Everest still top the charts?

The answer is a mountainous "no." That honor would go to Mauna Kea, an inactive volcano in Hawaii. Although its peak is 13,802 feet (4,205 m) above sea level - which is less than half the height of Everest, according to National Geographic - the majority of Mauna Kea is hidden below sea level. When measured from base to peak, Mauna Kea is 33,497 feet (10,211 m) tall, according to the United States Geological Survey, which puts it heads and shoulders above Mount Everest.

Should we, therefore, regard Mauna Kea as the tallest mountain on Earth?

"It all depends on the perspective you take," Price said. "If there were no oceans on our planet, there would be no debate! You could draw comparisons to the highest mountains on other bodies in our solar system, which have no oceans."

(Image credit: boydhendrikse via Getty Images)

Meanwhile, another contender, Mount Chimborazo in Ecuador, boasts a peak that is the farthest point from Earth's center.

Chimborazo isn't the tallest mountain in the Andes - it's not even in the top 30 - but its proximity to the equator is what makes all the difference. Earth is not a perfect sphere - technically, it's an oblate spheroid - and it bulges along the equator. This is a result of the force created by Earth's rotation. As a result, it means there is a difference of 13.29 miles (21.39 km) between the planet's polar radius (3,949.90 miles/6,356.75 km) and its equatorial radius (3,963.19 miles/6,378.14 km), according to the NASA Goddard Space Flight Center.

Chimborazo is just 1 degree south of the equator, where Earth's bulge is most prominent; this geographical quirk means Chimborazo's summit is 3,967 miles from Earth's core, making it 6,798 feet (2,072 m) farther away from the planet's center than the peak of Everest.

So, which of these three contenders for tallest mountain should take home first prize?

Mount Everest is the tallest mountain above sea level, while Mauna Kea can certainly claim to be the world's tallest mountain (when sea level isn't taken into account). It would be difficult to make a case for Chimborazo being the tallest, but "it's all a matter of perspective," Price admitted.

Regardless of the mountain you choose, its height will pale in comparison with Mars' Olympus Mons, the largest known volcano in the solar system. It has a height of around 16 miles (25 km), according to NASA, which is almost three times taller than Everest, and a base of 374 miles (601.9 km) in diameter, which is about the same distance separating San Francisco and Los Angeles (383.1 miles/616.5 km).

There is also an impact crater called Rheasilvia on the asteroid Vesta, which is part of the asteroid belt 100 million miles from Earth. At the center of this crater is a peak that scientists believe could be anywhere between 12 and 15.5 miles (20 and 25 km) in height, meaning it may be the tallest mountain in the solar system, according to the NASA Jet Propulsion Laboratory.
Originally published on Live Science.

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Is Mount Everest really the tallest mountain on Earth?

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(Image credit: Didier Marti via Getty Images) It's no secret that Mount Everest, the jewel in Nepal's Himalayan crown, is the world's premier mountain. It's one of those facts embedded in childhood, like knowing that Neil Armstrong was the first person to walk on the or that blue whales are the largest animals ever to have lived.

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The Earth has just one natural satellite known as the Moon. It travels around our planet at an average distance of 384,400 kilometers, approximately 30 times the diameter of Earth. The Moon consistently shows the same face to Earth due to gravitational forces, which have synchronized its rotation with our planet's, making the lunar day, spanning 29.5 days, align perfectly with the lunar month.

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From lighting up our skies to maintaining a geological record of our solar system's history, Earth's closest celestial neighbor plays a pivotal role in the studies of our planet and our solar system.

Earth's Moon is the brightest and largest object in our night sky. The Moon makes Earth a more livable planet by moderating our home planet's wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years.

The Moon was likely formed after a Mars-sized body collided with Earth several billion years ago.

Earth's only natural satellite is simply called "the Moon" because people didn't know other moons existed until Galileo Galilei discovered four moons orbiting Jupiter in 1610. In Latin, the Moon was called Luna, which is the main adjective for all things Moon-related: lunar.

On April 8, 2024, the Moon's shadow swept across North America, treating millions to a breathtaking view of a total...
Read the Story

Discover More Topics From NASA

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Earth's Moon is the brightest and largest object in our night sky. The Moon makes Earth a more livable planet by moderating our home planet's wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years.

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This photo was the world's first view of Earth taken near the moon.  

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It was snapped by the U.S. Lunar Orbiter I on August 23, 1966, when the spacecraft was just about to pass behind the moon on its 16th orbit.

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1. Earth isn’t actually round

2. Coral reefs are Earth’s largest living structure

3. Earth has a squishy interior

4. Antarctica is home to the largest ice sheet on Earth

5. The Moon is drifting away from Earth

6. Atacama is the driest place on Earth

7. Earth’s magnetic pole is creeping westward

8. Europe is the second smallest continent in size but the third largest in population

9. Tibetan plateau is Earth’s ‘third pole’

10. Trees are breathers

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We hope you enjoy this curated list of 10 of the most remarkable facts about Earth.

1. Earth isn't actually round

While this sounds like an elaborate joke, we're actually serious. Earth isn't flat, but it's not perfectly round either. Earth's rotation causes the planet to bulge at the equator and flatten at the poles, while the distribution of mass on Earth (which is not perfectly uniform) causes small variations in the gravitational pull at different locations on the planet. These variations are too small to be seen in pictures of Earth from space, so it appears round to the human eye.

The shape seen in the video above is not technically the shape of the planet, but its 'geoid', the shape of its mean sea-level surface extending around the entire globe. The map was produced using data collected from ESA's Gravity and Steady-State Ocean Circulation Explorer ( GOCE) and shows the most detailed map ever created of Earth's gravity field.

2. Coral reefs are Earth's largest living structure

Coral reefs are not only beautiful natural wonders, but also the largest living structure on Earth. These underwater ecosystems are made up of colonies of tiny animals called coral polyps, which build calcium carbonate skeletons that accumulate over time and form the complex structures we know as coral reefs.

Coral reefs are incredibly diverse and play a vital role in the ocean ecosystem, providing habitat and protection for many species, and acting as a natural barrier that helps to protect coastlines from storms and erosion.

Unfortunately, coral reefs are under threat from a range of environmental factors, including ocean acidification, rising temperatures and global warming. ESA research has shown how our ocean waters have become more acidic over the last three decades and how this is having a detrimental effect on marine life. By using satellite technology to measure ocean colour, temperature and salinity, scientists can track changes in ocean chemistry and detect areas where acidification is occurring.

Rising temperatures can also have a direct impact on coral reefs, causing coral bleaching, which occurs when corals expel the algae that live in their tissues and provide them with food. Coral bleaching can lead to the death of the coral, which can have knock-on effects on the wider ecosystem.

3. Earth has a squishy interior

Earth's interior is not solid, but rather has a semi-solid or 'squishy' consistency owing to high temperatures and pressures. This squishy consistency allows the mantle to flow and move over geological timescales, which is responsible for phenomena such as plate tectonics, volcanic activity and earthquakes.

One consequence of this squishy interior is a process known as post-glacial rebound. During the last ice age, large portions of Earth's surface were covered by glaciers, causing the underlying mantle to deform and sink. As the glaciers melted and receded, the mantle slowly rebounded back to its original position over thousands of years, causing the land above it to rise.

This process is still occurring today in places such as Canada, Scandinavia, and Greenland, where the land is still rebounding from the weight of the glaciers that once covered the region. Recent research had found that West Antarctica is rising faster than anywhere else in the world, thanks to data from ESA's GOCE gravity mission.

The study of post-glacial rebound provides important insights into the structure and behaviour of Earth's interior, and how it responds to changes in the surface environment over long timescales.

4. Antarctica is home to the largest ice sheet on Earth

More than six times as large as Greenland, Antarctica is the southernmost continent and is the coldest and windiest place on Earth - with temperatures that can drop as low as -89.2°C and winds that can exceed 320 km per hour.

Antarctica is home to the largest ice sheet on Earth, containing a staggering 30 million cubic kilometres of ice. This represents an incredible 70% of Earth's freshwater and 90% of its ice. As a result, changes to the Antarctic ice sheet can have significant implications for global sea levels and ocean currents.

Monitoring the Antarctic ice sheet is therefore of paramount importance and satellite data plays a crucial role in this effort. Data from satellites such as CryoSat, ESA's ice mission, allow scientists to track changes in the thickness and movement of the ice sheet over time, providing insights into how it is responding to a changing climate.

ESA has recently teamed up with NASA and the British Antarctic Survey ( BAS) to carry out an ambitious campaign in Antarctica which involved taking simultaneous measurements of sea ice from ESA's CryoSat and NASA's ICESat-2 satellites. This research is essential for informing policy decisions on issues such as climate change and sea level rise, and for developing strategies to mitigate their impact on coastal communities around the world.

5. The Moon is drifting away from Earth

You read that correctly! The Moon is gradually drifting away from Earth at a rate of approximately 4 cm per year. This phenomenon is caused by the Moon pulling on Earth's oceans creating tidal forces that produce a bulge of water on the side of Earth facing the Moon.

This bulge in turn creates a gravitational pull on the Moon, causing it to accelerate slightly and move further away from Earth. Over time, this process has caused the Moon to move farther away from Earth each year.

This gradual drift is not noticeable on a day-to-day basis, but over millions of years, it can have significant effects on Earth's rotation.

Today, most scientists believe the Moon is 'Earth's child' - a large body collided with Earth, destroying our planet's mantle and sending material into orbit from which the Moon formed. This 'big splash' theory would explain why the Moon's rocks are similar to those on Earth.

Bonus fun fact: Australia is actually wider than the Moon. The Moon sits at 3400 km in diameter, while Australia's diameter from east to west is almost 4000 km. The Moon, as a sphere, has more surface area, but it's still pretty impressive.

6. Atacama is the driest place on Earth

The Atacama Desert, located in South America, is widely considered to be the driest place on Earth, outside of the Antarctic dry valleys. This vast expanse of land spans over 100 000 sq km and receives an average of less than 1 mm of rainfall per year.

The harsh climate of the Atacama is due to a combination of factors including its location in a rain shadow caused by the Andes mountains, the presence of the cold Humboldt Current offshore and a lack of moisture-bearing winds.

Despite its arid conditions, the Atacama is home to a number of unique species of plants and animals that have adapted to survive in this harsh environment. The desert is also known for its stunning landscapes, including salt flats, geysers and towering volcanoes - making it a popular destination for adventurous travellers.

7. Earth's magnetic pole is creeping westward

Unlike our geographic North Pole, which is in a fixed location, Earth's magnetic north wanders. Until the early 1990s, the magnetic North Pole was known to lie some 1600 km south of true north, in Canada. Yet scientists realised that the location of magnetic north wasn't fixed and was drifting at a rate of 15 km a year. Since the 1990s, however, the drift of Earth's magnetic pole has turned into more of a sprint.

Its present speed is around 50-60 km a year and is making a dash towards Siberia at a pace not seen before. Why? Scientists studying the drift of Earth's magnetic north pole, using data from ESA's Swarm mission, have pinpointed a change in the circulation pattern of magnetic blobs deep below Earth's surface.

They learned a change in the flow underneath Canada has caused a patch of magnetic field at the edge of Earth's core, deep within the Earth, to be stretched out. This has weakened the Canadian patch and resulted in the pole shifting towards Siberia.

8. Europe is the second smallest continent in size but the third largest in population

Europe is known for its diverse cultures, rich history and stunning landmarks. Despite being the second smallest continent in size (after Australia), Europe is home to a staggering population of over 746 million people, making it the third largest continent in terms of population (after Asia and Africa).

Europe has one of the highest levels of urbanisation in the world, with over 75% of its population living in urban areas. With the world's population expected to reach 9.7 billion in 2050, we must increase efforts to understand and mitigate the challenges brought by rapid and unplanned urbanisation, air pollution, as well as issues related to the management of water and energy.

ESA and the German Aerospace Center (DLR), in collaboration with the Google Earth Engine team, have developed the World Settlement Footprint - the world's most comprehensive dataset on human settlement. Featuring data from the Copernicus Sentinel-1 and Sentinel-2 missions, this unprecedented collection of data on human settlement will advance our understanding of urbanisation on a global scale.

9. Tibetan plateau is Earth's 'third pole'

The Tibetan Plateau is often referred to as the 'third pole' owing to the amount of freshwater it contains. With over 46 000 glaciers, the Tibetan Plateau holds the largest reserve of freshwater outside of the North and South Poles.

These glaciers feed the rivers that run through the region, including the Mekong, Yangtze, and Yellow River, providing a vital source of water for millions of people in China and Southeast Asia.

The Tibetan Plateau's glaciers, along with other glaciers around the world, are under threat from climate change. Rising temperatures are causing the glaciers to melt at an unprecedented rate, which could have devastating consequences for the people and ecosystems that depend on them.

New findings have found that values of ice lost from Himalayan glaciers during 2000 to 2020 were, on average, underestimated by 6.5%. This discovery has critical implications for predicting the demise of the region's glaciers and for managing critical water resources.

10. Trees are breathers

Trees are one of the most effective tools we have to combat climate change. Forests are home to around 80% of biodiversity on land and tropical forests alone produce over 40% of the oxygen we breathe.

Covering around 30% of Earth's land surface, we depend on forests for our survival. Forests absorb around 8 Gigatonnes a year of carbon dioxide from the atmosphere and play a crucial role in the carbon cycle and climate system.

However, climate change, forest degradation and deforestation are causing much of this stored carbon to be released back into the atmosphere. Recent research found that recovering tropical forests were only successfully combatting a quarter of the current carbon emissions and indicates the importance of preserving and restoring our tropical forests.

To better understand the role of trees in regulating our planet's carbon cycle, ESA's upcoming mission called Biomass will use advanced radar technology to measure the amount of carbon stored in Earth's forests and other biomass, providing a more accurate assessment of carbon storage and uptake than ever before.

By monitoring changes in biomass over time, scientists will be able to assess the effectiveness of forest conservation efforts and better understand the impact of deforestation on our climate.

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We hope you enjoy this curated list of 10 of the most remarkable facts about Earth.