What is the surface like on this planet?
The surface of Venus is very different from the surface of the Earth. It is very dry and hot enough to melt lead. The pressure on the surface is very strong. It is the same as being 1 km (3,280 feet) below the surface of the sea on Earth.
Channels on the surface of Venus, looking like river channels on EarthChannels that look like rivers have formed on Venus. Scientists think these channels are formed from erupting lava. The lava flows along as it cools down, creating the channels. One feature only Venus seems to have is unusual volcanoes called arachnoids. These are volcanoes that have formed differently from other volcanoes we have found in the Solar System. We don't know exactly how they were formed. Venus also has volcanoes like those on Earth.
Parts of the surface of Venus look something like continents. The largest of these areas is called Ishtar Terra. Deep basins like those under the Earth's oceans have also been discovered. On Venus, though, they have no water. Features like mountain ranges and meteor craters have also been found on Venus. One of the highest mountains on Venus, Maxwell Montes, is about 11 km taller than Mount Everest, the highest mountain on Earth.
Tuesday, January 30, 2007
Venus
Venus is the second closest planet to the Sun. It is a terrestrial planet. This means that we think it was created in a similar way to our planet Earth and is made of rock.Venus is named after the Roman goddess of love. Sometimes it can be seen shining brightly just before dawn or just after sunset. Some people like the Aztecs and the Greeks, gave Venus two names – one for the morning and one for the evening.
If you were on Venus, it would pull you down almost as strongly as Earth. The atmosphere exerts a pressure at the surface more than 90 times Earth's normal sea-level pressure.
How big is Venus?
Earth and Venus ComparisonVenus is almost the same size as the Earth. This is one reason why Venus is sometimes thought of as Earth's "twin". Venus has a diameter of about 12,100 km.
If you were on Venus, it would pull you down almost as strongly as Earth. The atmosphere exerts a pressure at the surface more than 90 times Earth's normal sea-level pressure.
How big is Venus?
Earth and Venus ComparisonVenus is almost the same size as the Earth. This is one reason why Venus is sometimes thought of as Earth's "twin". Venus has a diameter of about 12,100 km.
Friday, January 26, 2007
What is Mercury made of?
What is Mercury made of?
The center of Mercury is made of iron in partly-molten (liquid) form. We know that it is iron at the center because the planet generates a magnetic field. It contains more iron for its size than any other planet in the Solar System. The rest of Mercury, its thick crust, is made of a special type of rock called silicate rocks. There are craters near the poles that are constantly in shadow. Some of these craters contain ice. There is a huge crater on Mercury called Caloris Basin. It was formed when a comet hit the planet and lava or molten rock filled the impact crater. The round wall of this crater is over 2km tall.
The center of Mercury is made of iron in partly-molten (liquid) form. We know that it is iron at the center because the planet generates a magnetic field. It contains more iron for its size than any other planet in the Solar System. The rest of Mercury, its thick crust, is made of a special type of rock called silicate rocks. There are craters near the poles that are constantly in shadow. Some of these craters contain ice. There is a huge crater on Mercury called Caloris Basin. It was formed when a comet hit the planet and lava or molten rock filled the impact crater. The round wall of this crater is over 2km tall.
A Year in Mercury
How long is a year on Mercury?
Mercury has the shortest year in the Solar System. It is about 88 Earth days long.
It used to be believed that the same side of Mercury always faced the Sun. In order for this to be true, Mercury would have to take the same amount of time to rotate (spin around) as it does to circle the sun. Through careful observation we now know that Mercury's rotation is somewhat faster than its orbit. Because of the way the orbit and rotation work together, on Mercury, a day is actually almost twice as long as a year.
Mercury has the shortest year in the Solar System. It is about 88 Earth days long.
It used to be believed that the same side of Mercury always faced the Sun. In order for this to be true, Mercury would have to take the same amount of time to rotate (spin around) as it does to circle the sun. Through careful observation we now know that Mercury's rotation is somewhat faster than its orbit. Because of the way the orbit and rotation work together, on Mercury, a day is actually almost twice as long as a year.
Merucury's Surface
Mercury has craters like those on the Earth's moon. The largest crater on Mercury is the Caloris Basin. It is about 1300 km wide. It was created by a huge asteroid hitting Mercury. The asteroid was probably 100 km wide, but it hit Mercury's surface so hard that it made a much bigger hole.
The surface also has big cliffs called scarps. They were made long ago when Mercury cooled down. It shrank, causing the surface to get wrinkled in some places. This wrinkling created the scarps.
There may also be ice on the top and bottom of Mercury. Like the Earth, these areas (called poles) don't get much warmth from the Sun. Any ice there won't melt.
It is very hot during the day (over 400°C) because Mercury is so close to the Sun. At night it is very cold because Mercury loses almost all its heat since there is almost no atmosphere to keep the warmth there. The temperature can fall to almost -275 degrees
How long is a day on this planet?
Mercury rotates (spins around) much more slowly than the Earth. It take Mercury 58 days to spin once. Because Mercury orbits the sun very quickly, a day on Mercury lasts longer than 58 days. If you were standing on Mercury, at the equator and timed how long it took the sun to go from directly overhead to sunset to sunrise and then rise directly overhead again, it would take 176 Earth days. These long days and nights allow for the temperatures to rise as high, and fall as low, as they do.
The surface also has big cliffs called scarps. They were made long ago when Mercury cooled down. It shrank, causing the surface to get wrinkled in some places. This wrinkling created the scarps.
There may also be ice on the top and bottom of Mercury. Like the Earth, these areas (called poles) don't get much warmth from the Sun. Any ice there won't melt.
It is very hot during the day (over 400°C) because Mercury is so close to the Sun. At night it is very cold because Mercury loses almost all its heat since there is almost no atmosphere to keep the warmth there. The temperature can fall to almost -275 degrees
How long is a day on this planet?
Mercury rotates (spins around) much more slowly than the Earth. It take Mercury 58 days to spin once. Because Mercury orbits the sun very quickly, a day on Mercury lasts longer than 58 days. If you were standing on Mercury, at the equator and timed how long it took the sun to go from directly overhead to sunset to sunrise and then rise directly overhead again, it would take 176 Earth days. These long days and nights allow for the temperatures to rise as high, and fall as low, as they do.
Mercury
The closest planet to the Sun is the Mercury. It is a terrestrial planet. That means a planet made from rock like Earth.Only one spacecraft, Mariner 10, has visited Mercury. Much of what we know about this planet came from this mission.
How big is Mercury?
Comparison of the size of Mercury to the Earth Mercury is 4879 km across. Mercury's diameter is just less than half the diameter of the Earth. It is the smallest planet in the Solar System. Only dwarf planets like Pluto are smaller. Mercury's small size and its closeness to the Sun sometimes make it difficult to see without a telescope or binoculars. The best time to spot Mercury in the sky is just after the sun goes down at night or shortly before it rises in the morning.
How big is Mercury?
Comparison of the size of Mercury to the Earth Mercury is 4879 km across. Mercury's diameter is just less than half the diameter of the Earth. It is the smallest planet in the Solar System. Only dwarf planets like Pluto are smaller. Mercury's small size and its closeness to the Sun sometimes make it difficult to see without a telescope or binoculars. The best time to spot Mercury in the sky is just after the sun goes down at night or shortly before it rises in the morning.
Tuesday, January 23, 2007
The Sun
The Sun is a star—the closest one to Earth. It is a large ball of very hot gas. The air we breathe and the Helium in a balloon are both gases. It is over 5,500 °C at the surface, and much hotter at the center, about 15 million °C. The Sun is made of mostly hydrogen (70%) and helium (28%). It turns much hydrogen into helium every second, thus creating heat and light.
The Sun makes light and heat that warms the surface of the Earth and allows plants to grow. We can get food from plants, and we can burn wood and other parts of plants to cook, warm our houses, and make cars go. Without the Sun there would be no life on Earth.
The Sun makes light and heat that warms the surface of the Earth and allows plants to grow. We can get food from plants, and we can burn wood and other parts of plants to cook, warm our houses, and make cars go. Without the Sun there would be no life on Earth.
How have we explored the Solar System?
Before the telescope, people explored the sky with their eyes. They saw how the planets seemed to wander through the sky. They learned to predict where the Sun, the moon, and planets would be in the sky. They built some observatories -- places for watching the sky. They watched the Sun and stars to tell the time of year. In China, they even knew when the moon would block the Sun. Most people thought that celestial bodies could cause war or peace on Earth.
After telescopes were first made, people kept making them better. Astronomers saw that planets are not like stars. They are worlds, like the Earth. They could see that some planets have moons.They began to think about what these worlds were like. At first, some thought that the other planets and moons had people or animals living on them. They thought about how it would be to live on these other worlds. Then they made telescopes better and saw that there are no plants or animals on the Moon or on Mars.
Twelve Astronauts walked on the Moon about 35 years ago. They brought rocks and dirt back to Earth.Spacecraft flew by Venus, Mars, and the outer planets. The pictures they took showed us a lot of what we know about these worlds.Robots landed on Mars in 1971, 1976, and 1997. They took thousands of pictures of the planets. Two robots, "Spirit" and "Opportunity", are working on Mars right now. They send photos and movies back to Earth. They also check rocks to find out what the rocks are made of.
So far, we have not found any life except on Earth. Maybe tiny one-celled life once lived on Mars. Maybe there is life under the ice on Jupiter's moon Europa. New spacecraft are being planned to look for life on these worlds.
After telescopes were first made, people kept making them better. Astronomers saw that planets are not like stars. They are worlds, like the Earth. They could see that some planets have moons.They began to think about what these worlds were like. At first, some thought that the other planets and moons had people or animals living on them. They thought about how it would be to live on these other worlds. Then they made telescopes better and saw that there are no plants or animals on the Moon or on Mars.
Twelve Astronauts walked on the Moon about 35 years ago. They brought rocks and dirt back to Earth.Spacecraft flew by Venus, Mars, and the outer planets. The pictures they took showed us a lot of what we know about these worlds.Robots landed on Mars in 1971, 1976, and 1997. They took thousands of pictures of the planets. Two robots, "Spirit" and "Opportunity", are working on Mars right now. They send photos and movies back to Earth. They also check rocks to find out what the rocks are made of.
So far, we have not found any life except on Earth. Maybe tiny one-celled life once lived on Mars. Maybe there is life under the ice on Jupiter's moon Europa. New spacecraft are being planned to look for life on these worlds.
Thursday, January 18, 2007
Discovery of the Solar System
Who discovered the Solar System?
Anyone who looks up at the sky enough can see seven bright objects. These are the Sun, our Moon, Mercury, Venus, Mars, Jupiter, and Saturn. People have known about them for a very long time. Ancient people thought they were related to gods. In Babylon, they named the days of the week after them. Almost everyone was sure that all these things were orbiting the Earth. They did not know we lived in a Solar System.
In 1543, Nicholaus Copernicus figured out that the planets orbit the Sun. Only the Moon orbits the Earth. But he was afraid to say so for most of his life. Then Galileo Galilei pointed a telescope at the sky. He found moons orbiting Jupiter. He was certain Copernicus was right, and he got in trouble for saying so. It took seventy years to convince scientists that the planets orbit the Sun. Now, almost everyone on Earth understands that we live in a Solar System.
People made better telescopes and found more things in the sky – moons, new planets, and asteroids. More things are being found today. Recently, astronomers found some things a lot like Pluto. One of them, called Eris, is bigger than Pluto. Maybe it should be called a planet. Maybe Pluto should not be called a planet any more.
Anyone who looks up at the sky enough can see seven bright objects. These are the Sun, our Moon, Mercury, Venus, Mars, Jupiter, and Saturn. People have known about them for a very long time. Ancient people thought they were related to gods. In Babylon, they named the days of the week after them. Almost everyone was sure that all these things were orbiting the Earth. They did not know we lived in a Solar System.
In 1543, Nicholaus Copernicus figured out that the planets orbit the Sun. Only the Moon orbits the Earth. But he was afraid to say so for most of his life. Then Galileo Galilei pointed a telescope at the sky. He found moons orbiting Jupiter. He was certain Copernicus was right, and he got in trouble for saying so. It took seventy years to convince scientists that the planets orbit the Sun. Now, almost everyone on Earth understands that we live in a Solar System.
People made better telescopes and found more things in the sky – moons, new planets, and asteroids. More things are being found today. Recently, astronomers found some things a lot like Pluto. One of them, called Eris, is bigger than Pluto. Maybe it should be called a planet. Maybe Pluto should not be called a planet any more.
About Mass
About mass
Everything is made out of matter. The amount of matter is called mass. Two bananas have twice the mass of one banana. The more mass a thing has, the more gravity pulls it and the more its gravity pulls other objects. We don't notice the pull from a banana because it is so much less than the pull from the Earth. If you stand on the ground and let go of a banana, gravity will pull it down towards the center of the Earth. It will hit the ground. If you could throw the banana hard enough at the right angle, it would go into orbit around the Earth. That is how rockets put astronauts into orbit. If you threw the banana really, REALLY hard in the right direction, it would fly away from Earth and never come back; but our arms are not that strong.
The force of gravity from anything is strongest very close to that thing, and weaker further from it. Scientists use weight to mean how hard gravity pulls us. Astronauts weigh less on the moon because it has less mass. It does not pull as hard. We actually weigh a tiny bit less on top of a tall mountain than we do in a lower place. This is because we are farther from most of the Earth.
Everything is made out of matter. The amount of matter is called mass. Two bananas have twice the mass of one banana. The more mass a thing has, the more gravity pulls it and the more its gravity pulls other objects. We don't notice the pull from a banana because it is so much less than the pull from the Earth. If you stand on the ground and let go of a banana, gravity will pull it down towards the center of the Earth. It will hit the ground. If you could throw the banana hard enough at the right angle, it would go into orbit around the Earth. That is how rockets put astronauts into orbit. If you threw the banana really, REALLY hard in the right direction, it would fly away from Earth and never come back; but our arms are not that strong.
The force of gravity from anything is strongest very close to that thing, and weaker further from it. Scientists use weight to mean how hard gravity pulls us. Astronauts weigh less on the moon because it has less mass. It does not pull as hard. We actually weigh a tiny bit less on top of a tall mountain than we do in a lower place. This is because we are farther from most of the Earth.
Wednesday, January 17, 2007
Our Solar System
Our Solar System
Planets are big balls of rock or gas that move around stars. We live on one we call the Earth, which moves around a star we call the Sun. There are at least seven other planets moving around the Sun and a lot of other smaller things as well. All these things together are called a system. The Latin word for the Sun is Sol, so we call this system the Solar System.
A long time ago, people didn't realize that all these things in the Solar System move around the Sun. They thought everything moved around the Earth, including the Sun. This seems sensible, because the Earth doesn't feel as if it's moving, does it?
About 500 years ago, however, a man named Copernicus suggested that all the planets moved around the Sun.[1] Then, about 100 years later, a man called Galileo began looking at the sky with a new invention: the telescope. He showed that it was very likely that all the planets moved around the Sun. Soon, more and more people started using telescopes to study the sky. They began to learn how the planets and the other things in the Solar System moved.
Now, we send rockets into space to learn more. Astronauts travel around the Earth. Some of them have landed on the the Moon. Robots can fly to other planets to take pictures. We can see things that people like Copernicus and Galileo could only dream about.
We can use very large telescopes to see what has happened to other stars. We compare pictures of distant stars with pictures of the Sun. We can use thousands of pictures of the planets to learn more about Earth. We use what we learn about all the things in the Solar System to figure out how it was formed.
A long time ago, people didn't realize that all these things in the Solar System move around the Sun. They thought everything moved around the Earth, including the Sun. This seems sensible, because the Earth doesn't feel as if it's moving, does it?
About 500 years ago, however, a man named Copernicus suggested that all the planets moved around the Sun. Then, about 100 years later, a man called Galileo began looking at the sky with a new invention: the telescope. He showed that it was very likely that all the planets moved around the Sun. Soon, more and more people started using telescopes to study the sky. They began to learn how the planets and the other things in the Solar System moved.
Now, we send rockets into space to learn more. Astronauts travel around the Earth. Some of them have landed on the the Moon. Robots can fly to other planets to take pictures. We can see things that people like Copernicus and Galileo could only dream about.
Our Solar System
The Sun
Mercury
Venus
Earth
Moon
Mars
Asteroid belt
Jupiter
Saturn
Uranus
Neptune
Pluto
Comets
Kuiper Belt
Oort Cloud
Glossary
We can use very large telescopes to see what has happened to other stars. We compare pictures of distant stars with pictures of the Sun. We can use thousands of pictures of the planets to learn more about Earth. We use what we learn about all the things in the Solar System to figure out how it was formed. We can also guess what might happen to it in the future.
What is the Solar System?
At the center of the Solar System is the Sun. It is a star, like the billions of other stars in the sky. The other stars are very, very far away, so they look tiny. The Sun is important to us because it gives us heat and energy that allows life. None of the life on Earth could exist without the Sun.
The rest of the things in the Solar System orbit (travel around) the Sun. The planets are the largest of these. Each planet is a little like the Earth. But the planets are also very different from each other.
Many of the planets have moons. A moon orbits a planet. Mercury has no moons. Earth has one. Jupiter has 63!
The planets closest to the Sun are called the inner planets. These are Mercury, Venus, Earth, and Mars. Then comes a big ring of asteroids, chunks of rock much smaller than planets. This ring is called the asteroid belt. Within the asteroid belt, there is a dwarf planet named Ceres. Then come the outer planets: Jupiter, Saturn, Uranus, and Neptune. Farther out there are two dwarf planets, Pluto and Eris.
Beyond the orbit of Neptune is another big ring of things like the asteroids, called the Kuiper belt. Kuiper (said "KYE-per") was the last name of the person who first wrote about it. Most of the things in the Kuiper belt are hard to see through telescopes.
After the Kuiper belt comes the Oort cloud. Scientists think this is where comets come from. It is very far away, many times farther away than Pluto is from the Sun (over a thousand times). It is near the edge of the Solar System.(Yes, "Oort" was the last name of the person who first wrote about it.)In between all the other things is dust. The pieces of dust are very far apart, but they shine in the light of the Sun. Before dawn, in September or October, they glow in the East. We call this the zodiacal glow.
When pieces of space dust hit the Earth's atmosphere, they burn brightly. We call them shooting stars or meteors.
The Sun creates solar wind—a kind of gas that blows away from the Sun into space. This gas travels out past the planets into outer space. The edge, where the solar wind meets the wind from other stars, is called the heliopause. That is about 100 times as far from us as the Earth is from the Sun. Beyond that is a lot of empty space. The nearest star to our Sun is thousands of times farther away than the size of the entire solar system. The Universe is a really huge place!
What holds it together?
Why do all of the planets orbit the Sun? Why do moons orbit planets? Why doesn't the Sun move off and leave the planets behind? The answer to all of these questions has to do with gravity. Gravity is a force that is a property of mass. It pulls things together.
We don't notice the pull from the Sun because it also pulls on the Earth by the same amount. But the Sun's gravity is strong enough to keep the Earth from shooting away. Even though the Earth is going fast, it keeps turning to go around the Sun. It is like they were tied together with an invisible string. In the same way, moons orbit many of the planets. They are kept there by gravity. The Sun itself does not sit still in space. The entire Solar System is orbiting the center of our galaxy. The whole thing stays together because of the force of gravity.
Planets are big balls of rock or gas that move around stars. We live on one we call the Earth, which moves around a star we call the Sun. There are at least seven other planets moving around the Sun and a lot of other smaller things as well. All these things together are called a system. The Latin word for the Sun is Sol, so we call this system the Solar System.
A long time ago, people didn't realize that all these things in the Solar System move around the Sun. They thought everything moved around the Earth, including the Sun. This seems sensible, because the Earth doesn't feel as if it's moving, does it?
About 500 years ago, however, a man named Copernicus suggested that all the planets moved around the Sun.[1] Then, about 100 years later, a man called Galileo began looking at the sky with a new invention: the telescope. He showed that it was very likely that all the planets moved around the Sun. Soon, more and more people started using telescopes to study the sky. They began to learn how the planets and the other things in the Solar System moved.
Now, we send rockets into space to learn more. Astronauts travel around the Earth. Some of them have landed on the the Moon. Robots can fly to other planets to take pictures. We can see things that people like Copernicus and Galileo could only dream about.
We can use very large telescopes to see what has happened to other stars. We compare pictures of distant stars with pictures of the Sun. We can use thousands of pictures of the planets to learn more about Earth. We use what we learn about all the things in the Solar System to figure out how it was formed.
A long time ago, people didn't realize that all these things in the Solar System move around the Sun. They thought everything moved around the Earth, including the Sun. This seems sensible, because the Earth doesn't feel as if it's moving, does it?
About 500 years ago, however, a man named Copernicus suggested that all the planets moved around the Sun. Then, about 100 years later, a man called Galileo began looking at the sky with a new invention: the telescope. He showed that it was very likely that all the planets moved around the Sun. Soon, more and more people started using telescopes to study the sky. They began to learn how the planets and the other things in the Solar System moved.
Now, we send rockets into space to learn more. Astronauts travel around the Earth. Some of them have landed on the the Moon. Robots can fly to other planets to take pictures. We can see things that people like Copernicus and Galileo could only dream about.
Our Solar System
The Sun
Mercury
Venus
Earth
Moon
Mars
Asteroid belt
Jupiter
Saturn
Uranus
Neptune
Pluto
Comets
Kuiper Belt
Oort Cloud
Glossary
We can use very large telescopes to see what has happened to other stars. We compare pictures of distant stars with pictures of the Sun. We can use thousands of pictures of the planets to learn more about Earth. We use what we learn about all the things in the Solar System to figure out how it was formed. We can also guess what might happen to it in the future.
What is the Solar System?
At the center of the Solar System is the Sun. It is a star, like the billions of other stars in the sky. The other stars are very, very far away, so they look tiny. The Sun is important to us because it gives us heat and energy that allows life. None of the life on Earth could exist without the Sun.
The rest of the things in the Solar System orbit (travel around) the Sun. The planets are the largest of these. Each planet is a little like the Earth. But the planets are also very different from each other.
Many of the planets have moons. A moon orbits a planet. Mercury has no moons. Earth has one. Jupiter has 63!
The planets closest to the Sun are called the inner planets. These are Mercury, Venus, Earth, and Mars. Then comes a big ring of asteroids, chunks of rock much smaller than planets. This ring is called the asteroid belt. Within the asteroid belt, there is a dwarf planet named Ceres. Then come the outer planets: Jupiter, Saturn, Uranus, and Neptune. Farther out there are two dwarf planets, Pluto and Eris.
Beyond the orbit of Neptune is another big ring of things like the asteroids, called the Kuiper belt. Kuiper (said "KYE-per") was the last name of the person who first wrote about it. Most of the things in the Kuiper belt are hard to see through telescopes.
After the Kuiper belt comes the Oort cloud. Scientists think this is where comets come from. It is very far away, many times farther away than Pluto is from the Sun (over a thousand times). It is near the edge of the Solar System.(Yes, "Oort" was the last name of the person who first wrote about it.)In between all the other things is dust. The pieces of dust are very far apart, but they shine in the light of the Sun. Before dawn, in September or October, they glow in the East. We call this the zodiacal glow.
When pieces of space dust hit the Earth's atmosphere, they burn brightly. We call them shooting stars or meteors.
The Sun creates solar wind—a kind of gas that blows away from the Sun into space. This gas travels out past the planets into outer space. The edge, where the solar wind meets the wind from other stars, is called the heliopause. That is about 100 times as far from us as the Earth is from the Sun. Beyond that is a lot of empty space. The nearest star to our Sun is thousands of times farther away than the size of the entire solar system. The Universe is a really huge place!
What holds it together?
Why do all of the planets orbit the Sun? Why do moons orbit planets? Why doesn't the Sun move off and leave the planets behind? The answer to all of these questions has to do with gravity. Gravity is a force that is a property of mass. It pulls things together.
We don't notice the pull from the Sun because it also pulls on the Earth by the same amount. But the Sun's gravity is strong enough to keep the Earth from shooting away. Even though the Earth is going fast, it keeps turning to go around the Sun. It is like they were tied together with an invisible string. In the same way, moons orbit many of the planets. They are kept there by gravity. The Sun itself does not sit still in space. The entire Solar System is orbiting the center of our galaxy. The whole thing stays together because of the force of gravity.
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