Venus is one of the nine planets in our Solar System. Venus is the second closest to the sun and the closest planet to earth. It has been known since prehistoric times a long time ago. Venus at a time was believed to have the same appearance as earth, a long time ago. Many think of venus as earth's sister in terms of planets. Venus is approximately 108, 208, 930 kilometres from the sun. Venus is the brightest
external image venus_magellan.jpg
planet which can be seen from the earth. Venus possesses thick clouds which are filled with gas and acid. The planet has an approximate mass of 4.869e24 kilograms. Venus does not have any traces of water however it is also believed that when Venus had an appearance which resembled earth, that it did hold some water. Venus's atmosphere is made up of 96% of Carbon Dioxide, 3.5% of Nitrogen and 0.5% of other smaller gases. This is very much different to that of earth as our planet of approximately 78% Nitrogen, 21% of Oxygen and other smaller gases. This could show that the earth may possibly morph appearance over time to resemble Venus's appearance. Due to the fact that venus has a hot atmosphere it is almost impossible for human's to sustain any life. Also because the planet does not possess any water at all, then it would be impossible for us humans to ever live life on Venus. Venus has been known for its ability to be extremely bright, just not as bright as the moon and the sun. Because Venus has a slow rotation of 243 earth days, it has no form of magnetic field's surrounding it.
The Earth is made out of many things. Deep inside Earth, near its center, lies Earth's core which is mostly made up of nickel and iron. Above the core is Earth's mantle, which is made up of rock containing silicon, iron, magnesium, aluminum, oxygen and other minerals. The rocky surface layer of Earth, called the crust, is made up of mostly oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium. Earth's surface is mainly covered with liquid water and its atmosphere is is mainly nitrogen and oxygen, with smaller amounts of carbon dioxide, water vapor and other gases.
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Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-wateroceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface. Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core. Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. A commentary bombardment during the early history of the planet played a role in the formation of the oceans. Later, asteroid impacts caused significant changes to the surface environment.
the earth's composition and structure
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Size comparison of inner planets (left to right): Mercury, Venus, Earth, and Mars
Size comparison of inner planets (left to right): Mercury, Venus, Earth, and Mars
Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas giant like Jupiter. It is the largest of the four solar terrestrial planets, both in terms of size and mass. Of these four planets, Earth also has the highest density, the highest surface gravity and the strongest magnetic field. Earth
Jupiter
Jupiter is a planet in outerspace. Jupiter is the fifth planet from the sun and is the largest of all eight known planets. Jupiter is more than twice the size of all the other planets combined and it has a mass more than 318 times of earth. It was named after the King of all gods, ruler of Olympus Jupiter. It is some times referred to as the gas giant along with Saturn, Uranus and Neptune. Jupiter is the third brightest object in the sky after the sun and venus and in the past it was sometimes referred to as the wandering star due to its brightness. Jupiter has four large moons by the names of Io, Europa, Ganymede and Callisto, these moons are now referred to as the Galilean moons. Over the years astronomers have been trying to reach Jupiter and they finally did in 1973 by Pioneer 10. Jupiter was orbited by a spacecraft called Galileo for aroung 8 years.
Jupiter
Jupiter
Jupiter does not have a solid surface it's gaseous material gets denser and what we see when we look at Jupiter is clouds high in it's atmospheres. Ninety percent of jupiter is hydrogen while the other ten percent is helium, along with those elements jupiter has traces of methane, water, ammonia and what is thought to be rock.They way Jupiter was formed and what it has in it is nearly the same as the Solar Nebula. Jupiter has a core of rocky material, and a This liquid metallic hydrogen is the same as what the sun has inside of it and is what powers Jupiter magnettic field. Their is water on Jupiter but not alot, and it hasd extremely high velocity winds.
external image 180px-Jupiter_interior.png
This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of metallic hydrogen.
THE GREAT RED SPOT
The great red spot is an oval shaped storm that is one of Jupiters most famous features. It was discovered around 300 years ago in the 17th century. This great red spot is 12,000 by 25,000 km, big enough to hold two Earths. The storm rotates clockwise and it takes around 6 days for it to complete one full turn.
Saturn, the sixth planet from the Sun, has the most spectacular set of rings in the solar system. We now know that Saturn has 59 moons in addition to its complex ring system. Saturn is one of the most recognizable and beautiful objects in the solar system . At the same time, however, this ringed giant has many secrets astronomers have struggled to uncover for centuries. Named for the Roman god Saturnas, the god of and father of Zeus, Saturn was first observed through a telescope in 1610 by Galileo Galilei. We have learned much about this unusual planet in four hundred years. The sixth planet from the Sun, Saturn is the second-largest in the solar system, outclassed only by Jupiter. It is a gas giant, composed of ninety-three percent, six percent helium, and trace amounts of other gases that contribute to its striped appearance. Saturn has four principle layers. The core is solid rock, roughly Earth-size, followed by a layer of liquid metallic hydrogen. Further away from the core, the metallic hydrogen becomes liquid molecular hydrogen, and the topmost layer is gaseous. As a gas giant, Saturn has no distinct surface, but great ice and ammonia clouds form distinct atmospheric bands and stripes. The planet's rotation creates high winds, up to 1,100 miles (1,800 kilometers) per hour at the equator, and as Saturn reaches the end of its summer when the atmosphere is warmest, an immense storm appears. It was first observed in 1876, and has been christened the Great White Spot because of its visibility and brilliance. It recurs approximately every thirty years.
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Uranus
Uranus is a gas planet in outer space. Uranus is the seventh planet from the sun and the thirdlargest planet in the universe.Uranus has a larger diameter than neptune but neptune is higher in mass than Uranua.Uranus was named after the ancient Greek name for Heaven, the home of the gods.UranusUranus was the first planet discovered and it was discovered by William Herschel. Uranus has only been visited by one spacecraft, Voyager 2 on Jan 24 1986. Most of the planets spin on an axis nearly perpendicular to the plane of the eclipticbut Uranus' axis is almost parallel to the ecliptic, which means unlike other planets it looks like it is on a verticle axis.
Unanus, having a verticle axis
Unanus, having a verticle axis
Uranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium, this is different to Jupiter and Saturn which are mostly hydrogen. Uranus has a core like Jupiter and Saturn without the massive amounts of liquid metallic hydrogen. Uranus does not has a rocky core with it's atmosphere about 83% hydrogen, 15% helium and 2% methane. Uranus has rings and are very dark and they are composed of large particles that are around 10 meters in diameter with dust surrounding them. Uranus has 11 known rings and they are all very faint. The brightest is known as the Epsilon ring. All rings surrounding uranus are called the Uranian rings. The Uranian rings were the first after Saturn's to be discovered. This was of considerable importance since we now know that rings are a common feature of planets, not a peculiarity of Saturn alone.
external image UranusRings.jpg
WHATS WITH THE COLOUR?
Uranus gets its blue-green color from methane gas. The light from the sun is reflected from the top of the clouds of Uranus' , which are under a layer of methane gas. As the reflected sunlight passes back through this layer, the methane gas absorbs the red part of the light, which lets the blue part pass through, resulting in the blue-green color that we see.
FACTS ON URANUS
Distance from the sun: 2,870,972,200 km
Equatorial Radius: 25,559 km
Volume: 68,330,000,000,000 km3
Mass: 86,849,000,000,000,000,000,000,
000 kg
Density: 1.30 g/cm3
Surface area: 8,115,600,000 km2
Orbital Circumference 17,620,000,000 km
URANUS HAS 27 MOONS (They have links to their respected pages)
Neptune is the eighth planet from the Sun. However, every couple hundred years, Pluto's orbit brings it closer, making Neptune the ninth planet from the Sun momentarily. The last time this happened was in 1979. Pluto stayed the eighth planet in the solar system for 20 years, until its orbit bypassed Neptune in 1999. This event won't happen again for another 242 years. Neptune is also the fourth largest planet in the solar system, big enough to fit 60 Earths inside. Neptune is approximately 3 billion miles from the Sun and it takes about 165 years for Neptune to orbit the Sun once—meaning that one year on Neptune is equivalent to 165 Earth years.A Neptune day is only 16 hours, however, which means that the planet rotates fairly quickly. Neptune may be the windiest planet in our solar system, often having winds that reach over 1,200 miles per hour. The winds are so strong, that at one time Neptune's Great Dark Spot was blown across the planet at 700 miles per hour. The dark spot is about the same size as Earth. These strong winds are a result of the planet's speed of rotation and the vast temperature differences on the planet.
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At nearly 17 times the size of earth, neptune is the fourth-largest planet as well as one of the slowest moving. Lying at the outer reaches of the solar system, Neptune trudges through space, taking165 earth years to orbit the sun. Discovery and History It was Italian scientist and scholar Galileo who first observed Neptune, spotting the planet in 1613. He was only able to glimpse the planet for two nights, and was thus unable to gain a clear understanding of its movements. Because of this lack of information, galileo mistook the planet for a star. When Neptune's identity was finally uncovered in 1846, it was because of the discovery of another planet, Uranus. Astronomers had noted that Uranus did not behave as it should according to Newton's Laws of Motion. The reason, it was thought, must be that some other planet was exerting an influence on Uranus' orbit. Two astronomers, working independently, predicted the location of the unknown planet based on observations of Jupiter, Saturn and Uranus.What followed was an international dispute, with both the English and the French seeking credit and the right to name the new planet. Today, both countries, and both astronomers, are credited with the discovery.
Mars
The planet Mars is the fourth planet from the sun. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts directly with the Martian ionosphere, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer. The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water. Atmospheric pressure is required to keep water in the liquid state. Mars gets its light source from the sun. If you ever go to Mars, you can still see where you are and what is around you. no human can live on mars. it is physically impossible because there is no water and volcanos are errupting everyday. If a town was living on a volcano, they would of all been dead in a matter of seconds. Mars was formed at the same time as the rest of the solar system, from a large spinning disk of gas and dust. Astronomers think that all this happened about 4.6 billion years ago! So Mars is about 4.6 billion years old. On mars, it has a mountain three times the size of Mt Everest. Mars is also known as the red planet because it is covered with red dust which makes it look red.
The Red Planet, Mars
Mercury
1. Crust - 100–300 km thick 2. Mantle - 600 km thick 3. Core - 1,800 km radius
1. Crust - 100–300 km thick
2. Mantle - 600 km thick
3. Core - 1,800 km radius
Mercury’s density can be used to infer details of its inner structure. While the Earth’s high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not nearly as strongly compressed. Therefore, for it to have such a high density, its core must be large and rich in iron. Geologists estimate that Mercury’s core occupies about 42% of its volume; for Earth this proportion is 17%. Recent research strongly suggests Mercury has a molten core.
Surrounding the core is a 600 km mantle. It is generally thought that early in Mercury’s history, a giant impact with a body several hundred kilometers across stripped the planet of much of its original mantle material, resulting in the relatively thin mantle compared to the sizable core.
Mercury's core has a higher iron content than that of any other major planet in the Solar System, and several theories have been proposed to explain this. The most widely accepted theory is that Mercury originally had a metal-silicate ratio similar to common chondrite meteors, thought to be typical of the Solar System's rocky matter, and a mass approximately 2.25 times its current mass. However, early in the solar system’s history, Mercury may have been struck by a planetesimal of approximately 1/6 that mass.
A third hypothesis proposes that the solar nebula caused drag on the particles from which Mercury was accreting, which meant that lighter particles were lost from the accreting material.
Mercury is one of the four terrestrial planets; rocky bodies like the Earth. It is the smallest of the four, with an equatorial radius of 2439.7 km. Mercury is even smaller—albeit more massive—than the largest natural satellites in the solar system, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water.
(For all the Planets visit their seperate pages)
Venus
Venus is one of the nine planets in our Solar System. Venus is the second closest to the sun and the closest planet to earth. It has been known since prehistoric times a long time ago. Venus at a time was believed to have the same appearance as earth, a long time ago. Many think of venus as earth's sister in terms of planets. Venus is approximately 108, 208, 930 kilometres from the sun. Venus is the brightest
Resources:
http://www.nasa.gov/worldbook/venus_worldbook.html</span>
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus</span>
http://www.solarviews.com/eng/venus.htm</span>
http://www.nineplanets.org/venus.html</span>
Earth
The Earth is made out of many things. Deep inside Earth, near its center, lies Earth's core which is mostly made up of nickel and iron. Above the core is Earth's mantle, which is made up of rock containing silicon, iron, magnesium, aluminum, oxygen and other minerals. The rocky surface layer of Earth, called the crust, is made up of mostly oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium. Earth's surface is mainly covered with liquid water and its atmosphere is is mainly nitrogen and oxygen, with smaller amounts of carbon dioxide, water vapor and other gases.
Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface. Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.
Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. A commentary bombardment during the early history of the planet played a role in the formation of the oceans. Later, asteroid impacts caused significant changes to the surface environment.
the earth's composition and structure
Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas giant like Jupiter. It is the largest of the four solar terrestrial planets, both in terms of size and mass. Of these four planets, Earth also has the highest density, the highest surface gravity and the strongest magnetic field.
Earth
Jupiter
Jupiter is a planet in outerspace. Jupiter is the fifth planet from the sun and is the largest of all eight known planets. Jupiter is more than twice the size of all the other planets combined and it has a mass more than 318 times of earth. It was named after the King of all gods, ruler of Olympus Jupiter. It is some times referred to as the gas giant along with Saturn, Uranus and Neptune. Jupiter is the third brightest object in the sky after the sun and venus and in the past it was sometimes referred to as the wandering star due to its brightness. Jupiter has four large moons by the names of Io, Europa, Ganymede and Callisto, these moons are now referred to as the Galilean moons. Over the years astronomers have been trying to reach Jupiter and they finally did in 1973 by Pioneer 10. Jupiter was orbited by a spacecraft called Galileo for aroung 8 years.
Jupiter does not have a solid surface it's gaseous material gets denser and what we see when we look at Jupiter is clouds high in it's atmospheres. Ninety percent of jupiter is hydrogen while the other ten percent is helium, along with those elements jupiter has traces of methane, water, ammonia and what is thought to be rock.They way Jupiter was formed and what it has in it is nearly the same as the Solar Nebula. Jupiter has a core of rocky material, and a This liquid metallic hydrogen is the same as what the sun has inside of it and is what powers Jupiter magnettic field. Their is water on Jupiter but not alot, and it hasd extremely high velocity winds.
THE GREAT RED SPOT
The great red spot is an oval shaped storm that is one of Jupiters most famous features. It was discovered around 300 years ago in the 17th century. This great red spot is 12,000 by 25,000 km, big enough to hold two Earths. The storm rotates clockwise and it takes around 6 days for it to complete one full turn.
External Links
SATURN
Saturn, the sixth planet from the Sun, has the most spectacular set of rings in the solar system. We now know that Saturn has 59 moons in addition to its complex ring system. Saturn is one of the most recognizable and beautiful objects in the solar system . At the same time, however, this ringed giant has many secrets astronomers have struggled to uncover for centuries. Named for the Roman god Saturnas, the god of and father of Zeus, Saturn was first observed through a telescope in 1610 by Galileo Galilei. We have learned much about this unusual planet in four hundred years. The sixth planet from the Sun, Saturn is the second-largest in the solar system, outclassed only by Jupiter. It is a gas giant, composed of ninety-three percent, six percent helium, and trace amounts of other gases that contribute to its striped appearance. Saturn has four principle layers. The core is solid rock, roughly Earth-size, followed by a layer of liquid metallic hydrogen. Further away from the core, the metallic hydrogen becomes liquid molecular hydrogen, and the topmost layer is gaseous. As a gas giant, Saturn has no distinct surface, but great ice and ammonia clouds form distinct atmospheric bands and stripes. The planet's rotation creates high winds, up to 1,100 miles (1,800 kilometers) per hour at the equator, and as Saturn reaches the end of its summer when the atmosphere is warmest, an immense storm appears. It was first observed in 1876, and has been christened the Great White Spot because of its visibility and brilliance. It recurs approximately every thirty years.Uranus
Uranus is a gas planet in outer space. Uranus is the seventh planet from the sun and the third largest planet in the universe. Uranus has a larger diameter than neptune but neptune is higher in mass than Uranua. Uranus was named after the ancient Greek name for Heaven, the home of the gods. UranusUranus was the first planet discovered and it was discovered by William Herschel. Uranus has only been visited by one spacecraft, Voyager 2 on Jan 24 1986. Most of the planets spin on an axis nearly perpendicular to the plane of the eclipticbut Uranus' axis is almost parallel to the ecliptic, which means unlike other planets it looks like it is on a verticle axis.
Uranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium, this is different to Jupiter and Saturn which are mostly hydrogen. Uranus has a core like Jupiter and Saturn without the massive amounts of liquid metallic hydrogen. Uranus does not has a rocky core with it's atmosphere about 83% hydrogen, 15% helium and 2% methane. Uranus has rings and are very dark and they are composed of large particles that are around 10 meters in diameter with dust surrounding them. Uranus has 11 known rings and they are all very faint. The brightest is known as the Epsilon ring. All rings surrounding uranus are called the Uranian rings. The Uranian rings were the first after Saturn's to be discovered. This was of considerable importance since we now know that rings are a common feature of planets, not a peculiarity of Saturn alone.
WHATS WITH THE COLOUR?
Uranus gets its blue-green color from methane gas. The light from the sun is reflected from the top of the clouds of Uranus' , which are under a layer of methane gas. As the reflected sunlight passes back through this layer, the methane gas absorbs the red part of the light, which lets the blue part pass through, resulting in the blue-green color that we see.
FACTS ON URANUS
Distance from the sun:
2,870,972,200 km
Equatorial Radius:
25,559 km
Volume:
68,330,000,000,000 km3
Mass:
86,849,000,000,000,000,000,000,
000 kg
Density:
1.30 g/cm3
Surface area:
8,115,600,000 km2
Orbital Circumference
17,620,000,000 km
URANUS HAS 27 MOONS (They have links to their respected pages)
1. Cordelia
2. Ophelia
3. Bianca
4. Cressida
5. Desdemona
6. Juliet
7. Portia
8. Rosalind
9. Mab
10. Belinda
11. Perdita
12. Puck
13. Cupid
14. Miranda
15. Francisco
16. Ariel
17. Umbriel
18. Titania
19. Oberon
20. Caliban
21. Stephano
22. Trinculo
23. Sycorax
24. Margaret
25. Prospero
26. Setebos
27. Ferdinand
EXTERNAL LINKS
Neptune
Neptune is the eighth planet from the Sun. However, every couple hundred years, Pluto's orbit brings it closer, making Neptune the ninth planet from the Sun momentarily. The last time this happened was in 1979. Pluto stayed the eighth planet in the solar system for 20 years, until its orbit bypassed Neptune in 1999. This event won't happen again for another 242 years. Neptune is also the fourth largest planet in the solar system, big enough to fit 60 Earths inside. Neptune is approximately 3 billion miles from the Sun and it takes about 165 years for Neptune to orbit the Sun once—meaning that one year on Neptune is equivalent to 165 Earth years.A Neptune day is only 16 hours, however, which means that the planet rotates fairly quickly. Neptune may be the windiest planet in our solar system, often having winds that reach over 1,200 miles per hour. The winds are so strong, that at one time Neptune's Great Dark Spot was blown across the planet at 700 miles per hour. The dark spot is about the same size as Earth. These strong winds are a result of the planet's speed of rotation and the vast temperature differences on the planet.
At nearly 17 times the size of earth, neptune is the fourth-largest planet as well as one of the slowest moving. Lying at the outer reaches of the solar system, Neptune trudges through space, taking165 earth years to orbit the sun. Discovery and History It was Italian scientist and scholar Galileo who first observed Neptune, spotting the planet in 1613. He was only able to glimpse the planet for two nights, and was thus unable to gain a clear understanding of its movements. Because of this lack of information, galileo mistook the planet for a star. When Neptune's identity was finally uncovered in 1846, it was because of the discovery of another planet, Uranus. Astronomers had noted that Uranus did not behave as it should according to Newton's Laws of Motion. The reason, it was thought, must be that some other planet was exerting an influence on Uranus' orbit. Two astronomers, working independently, predicted the location of the unknown planet based on observations of Jupiter, Saturn and Uranus.What followed was an international dispute, with both the English and the French seeking credit and the right to name the new planet. Today, both countries, and both astronomers, are credited with the discovery.
Mars
The planet Mars is the fourth planet from the sun. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts directly with the Martian ionosphere, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer. The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water. Atmospheric pressure is required to keep water in the liquid state. Mars gets its light source from the sun. If you ever go to Mars, you can still see where you are and what is around you. no human can live on mars. it is physically impossible because there is no water and volcanos are errupting everyday. If a town was living on a volcano, they would of all been dead in a matter of seconds. Mars was formed at the same time as the rest of the solar system, from a large spinning disk of gas and dust. Astronomers think that all this happened about 4.6 billion years ago! So Mars is about 4.6 billion years old. On mars, it has a mountain three times the size of Mt Everest. Mars is also known as the red planet because it is covered with red dust which makes it look red.
Mercury
2. Mantle - 600 km thick
3. Core - 1,800 km radius
Mercury’s density can be used to infer details of its inner structure. While the Earth’s high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not nearly as strongly compressed. Therefore, for it to have such a high density, its core must be large and rich in iron. Geologists estimate that Mercury’s core occupies about 42% of its volume; for Earth this proportion is 17%. Recent research strongly suggests Mercury has a molten core.
Surrounding the core is a 600 km mantle. It is generally thought that early in Mercury’s history, a giant impact with a body several hundred kilometers across stripped the planet of much of its original mantle material, resulting in the relatively thin mantle compared to the sizable core.
Mercury's core has a higher iron content than that of any other major planet in the Solar System, and several theories have been proposed to explain this. The most widely accepted theory is that Mercury originally had a metal-silicate ratio similar to common chondrite meteors, thought to be typical of the Solar System's rocky matter, and a mass approximately 2.25 times its current mass. However, early in the solar system’s history, Mercury may have been struck by a planetesimal of approximately 1/6 that mass.
A third hypothesis proposes that the solar nebula caused drag on the particles from which Mercury was accreting, which meant that lighter particles were lost from the accreting material.
Mercury is one of the four terrestrial planets; rocky bodies like the Earth. It is the smallest of the four, with an equatorial radius of 2439.7 km. Mercury is even smaller—albeit more massive—than the largest natural satellites in the solar system, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water.