Our Amazing Our Amazing Solar SystemSolar System

What is a planet?What is a planet? A planet is a large space object which A planet is a large space object which revolves

around a star. It also around a star. It also reflects that star's light. Eight that star's light. Eight planets have been discovered in our planets have been discovered in our solar system. system. Mercury, Venus, Earth, and Mars are the planets Mercury, Venus, Earth, and Mars are the planets closest to the Sun. They are called the inner planets. closest to the Sun. They are called the inner planets. The inner planets are made up mostly of rock. The The inner planets are made up mostly of rock. The outer planets are Jupiter, Saturn, Uranus, and outer planets are Jupiter, Saturn, Uranus, and Neptune. Jupiter, Saturn, Uranus, and Neptune are Neptune. Jupiter, Saturn, Uranus, and Neptune are large balls of large balls of gases with rings around them. All eight with rings around them. All eight planets travel around the Sun in a different planets travel around the Sun in a different orbit. In . In its orbit, there are not many other objects like the its orbit, there are not many other objects like the planet. planet.

Dwarf planets are objects that are similar to planets Dwarf planets are objects that are similar to planets except that they orbit the Sun in areas where there except that they orbit the Sun in areas where there are many similar objects.are many similar objects.

Inner PlanetsInner Planets

MercuryMercury

VenusVenus

EarthEarth

MarsMars

MercuryMercury Mercury is the smallest Mercury is the smallest

planet in our planet in our solar system. system. Mercury is about the Mercury is about the same size as our Moon. It same size as our Moon. It is very close to the Sun. is very close to the Sun. Mercury travels around Mercury travels around the Sun faster than any the Sun faster than any other planet. That is how other planet. That is how it got its name. It was it got its name. It was named after Mercury, the named after Mercury, the swift messenger of the swift messenger of the gods in ancient Roman gods in ancient Roman mythology. .

Mercury can only be seen Mercury can only be seen from Earth just before from Earth just before sunrise or just after sunset, sunrise or just after sunset, but not in the middle of the but not in the middle of the night. That is because night. That is because Mercury always appears Mercury always appears near the Sun when viewed near the Sun when viewed from Earth. Mercury has a from Earth. Mercury has a very thin very thin atmosphere. . Humans would not be able Humans would not be able to live there. The surface of to live there. The surface of Mercury has holes in it Mercury has holes in it where objects such as where objects such as meteorites and and asteroids crashed into it.crashed into it.

VenusVenus Venus and Earth are almost the Venus and Earth are almost the

same size. Venus is the closest same size. Venus is the closest planet to Earth, but it does not planet to Earth, but it does not have oceans or human life like have oceans or human life like Earth. Venus gets so hot during Earth. Venus gets so hot during the day that it could melt a lead the day that it could melt a lead cannonball. The temperature cannonball. The temperature rises to 484 degrees rises to 484 degrees Celsius on on the side facing the Sun. Venus the side facing the Sun. Venus has very thick, rapidly spinning has very thick, rapidly spinning clouds which cover its surface. clouds which cover its surface. These clouds hold heat in. That is These clouds hold heat in. That is why Venus gets so hot. These why Venus gets so hot. These clouds also clouds also reflect sunlight. That sunlight. That is why Venus appears so bright is why Venus appears so bright to us here on Earth. There are to us here on Earth. There are constant thunderstorms in these constant thunderstorms in these clouds. Venus has several large clouds. Venus has several large inactive inactive volcanoes. Much of the . Much of the surface is covered by old lava surface is covered by old lava flows from these volcanoes.flows from these volcanoes.

Venus is unusual because it Venus is unusual because it rotates in a direction opposite in a direction opposite that of all of the other planets. that of all of the other planets. Venus spins very slowly as it Venus spins very slowly as it orbits the Sun. the Sun.

That is why Venus appears so That is why Venus appears so bright to us here on Earth. bright to us here on Earth. There are constant There are constant thunderstorms in these thunderstorms in these clouds. Venus has several clouds. Venus has several large inactive large inactive volcanoes. . Much of the surface is Much of the surface is covered by old lava flows covered by old lava flows from these volcanoes.from these volcanoes.

Venus is unusual because it Venus is unusual because it rotates in a direction opposite in a direction opposite that of all of the other planets. that of all of the other planets. Venus spins very slowly as it Venus spins very slowly as it orbits the Sun. the Sun.

EarthEarth Earth is the third closest planet to the Sun. It has an Earth is the third closest planet to the Sun. It has an

atmosphere made up of many different made up of many different gases, but , but mainly it is nitrogen and oxygen. The atmosphere mainly it is nitrogen and oxygen. The atmosphere gives us air to breathe. We live on the planet Earth. gives us air to breathe. We live on the planet Earth.

The Earth The Earth orbits around the Sun. It takes one year to around the Sun. It takes one year to go around the Sun one complete time. The Earth also go around the Sun one complete time. The Earth also rotates, or spins, on its , or spins, on its axis. It takes one day to spin . It takes one day to spin around one complete time. The Earth's axis is not around one complete time. The Earth's axis is not straight up and down, but tilted a little bit. This tilt is straight up and down, but tilted a little bit. This tilt is responsible for us having seasons. Otherwise, the responsible for us having seasons. Otherwise, the temperature would be pretty much the same all year temperature would be pretty much the same all year long. long.

Seventy percent of the Earth's surface is covered by Seventy percent of the Earth's surface is covered by water. The remaining 30 percent is covered by water. The remaining 30 percent is covered by mountains, mountains, volcanoes, deserts, , deserts, plains, and , and valleys. .

Mars:Mars:The Red PlanetThe Red Planet

The temperature on Mars can be very, very cold. On its The temperature on Mars can be very, very cold. On its warmest day, Mars can still be a very cold place. At the warmest day, Mars can still be a very cold place. At the top and bottom of the planet are top and bottom of the planet are poles just like on Earth. just like on Earth. During the Martian winter, ice caps can be seen at the During the Martian winter, ice caps can be seen at the poles. poles.

Space probes have landed on Mars. These probes were Space probes have landed on Mars. These probes were sent on a fact-finding mission by the United States. They sent on a fact-finding mission by the United States. They performed experiments on the Martian dirt and performed experiments on the Martian dirt and atmosphere. The dirt was found to contain clay which was . The dirt was found to contain clay which was rich in iron. The iron is what gives Mars its red color. rich in iron. The iron is what gives Mars its red color.

Mars has many Mars has many craters which were formed by which were formed by meteorites or or asteroids hitting it. Mars also has some of the tallest hitting it. Mars also has some of the tallest volcanoes and some of the deepest and some of the deepest valleys in our in our solar system. Mars has two moons, Phobos and Deimos which system. Mars has two moons, Phobos and Deimos which have unusual shapes. Scientists think these potato-shaped have unusual shapes. Scientists think these potato-shaped moons were once asteroids captured by Mars' moons were once asteroids captured by Mars' gravitational pull . .

The Outer PlanetsThe Outer Planets

JupiterJupiter

SaturnSaturn

UranusUranus

NeptuneNeptune

Jupiter:Jupiter: The Largest PlanetThe Largest Planet

Jupiter is so large that all Jupiter is so large that all of the other planets in of the other planets in the the solar system could fit system could fit inside of it. inside of it.

Jupiter is a large Jupiter is a large gas planet whose clouds planet whose clouds change colors daily. This change colors daily. This planet is made mostly of planet is made mostly of hydrogen and helium hydrogen and helium gases. Jupiter gives off gases. Jupiter gives off two times more heat than two times more heat than it gets from the Sun. It it gets from the Sun. It shines very brightly in shines very brightly in the night sky for nine the night sky for nine months of the year when months of the year when it is closest to Earth.it is closest to Earth.

Huge areas of swirling gases Huge areas of swirling gases can be found in Jupiter's can be found in Jupiter's atmosphere. The largest . The largest swirling area of gas is called swirling area of gas is called the Great Red Spot. Scientists the Great Red Spot. Scientists believe this is a large believe this is a large hurricane-like storm which has -like storm which has lasted for hundreds of years. lasted for hundreds of years. Large Large bolts of lightning have of lightning have also been seen in Jupiter's also been seen in Jupiter's atmosphere. Pictures taken by atmosphere. Pictures taken by space probes have shown thin have shown thin rings around Jupiter. Jupiter rings around Jupiter. Jupiter has forty-nine named moons has forty-nine named moons (and may have as many as (and may have as many as 63!). One of Jupiter's moons, ). One of Jupiter's moons, Io, has active , has active volcanoes on it. on it. Areas on Io that are near the Areas on Io that are near the volcanoes are very, very hot.volcanoes are very, very hot.

Saturn:Saturn:The Ringed PlanetThe Ringed Planet

Saturn is a very large Saturn is a very large gas planet which spins very rapidly planet which spins very rapidly on its on its axis. It spins so fast that it flattens out the top and . It spins so fast that it flattens out the top and the bottom of the planet. The fast spin also causes Saturn the bottom of the planet. The fast spin also causes Saturn to to bulge at its equator. Saturn's at its equator. Saturn's atmosphere has winds has winds which can blow at over 1800 which can blow at over 1800 kilometers per hour! The per hour! The white spots on Saturn are believed to be powerful storms. white spots on Saturn are believed to be powerful storms. Saturn is surrounded by over 1000 rings made of ice and Saturn is surrounded by over 1000 rings made of ice and dust. Some of the rings are very thin and some are very dust. Some of the rings are very thin and some are very thick. The size of the thick. The size of the particles in the rings range from in the rings range from pebble-size to house-size. Scientists believe that the pebble-size to house-size. Scientists believe that the particles came from the destruction of moons circling the particles came from the destruction of moons circling the planet. As planet. As comets and and meteorites smashed the moons, smashed the moons, Saturn's Saturn's gravitational pull shaped the particles into rings. shaped the particles into rings. Saturn has Saturn has at least 52 moons. Some of these moons . Some of these moons orbit the planet within the rings, creating the planet within the rings, creating gaps in the rings. in the rings.

Uranus: Uranus: Neptune’s TwinNeptune’s Twin

Uranus is one of the smaller Uranus is one of the smaller gas giants in our giants in our solar system, but it is still large enough to hold 64 planets system, but it is still large enough to hold 64 planets the size of Earth. the size of Earth.

Uranus tilts over so far on its Uranus tilts over so far on its axis that it that it rotates on its on its side. Because of this, its side. Because of this, its poles are sometimes pointed are sometimes pointed almost directly at the Sun. Uranus' almost directly at the Sun. Uranus' atmosphere is is made up of hydrogen, helium, and methane. The made up of hydrogen, helium, and methane. The temperature in the upper atmosphere is very cold. The temperature in the upper atmosphere is very cold. The cold methane gas is what gives Uranus its blue-green cold methane gas is what gives Uranus its blue-green color. The rapid rotation of Uranus causes winds up to color. The rapid rotation of Uranus causes winds up to 600 600 kilometers per hour to blow in its atmosphere. per hour to blow in its atmosphere. Uranus has eleven known rings which contain dark, Uranus has eleven known rings which contain dark, boulder-sized -sized particles. Uranus has 27 named moons. . Uranus has 27 named moons. Some of these moons are less than 100 kilometers Some of these moons are less than 100 kilometers wide and black as coal. wide and black as coal.

Neptune:Neptune:The Blue PlanetThe Blue Planet

It is so cold on Neptune that It is so cold on Neptune that you would need skin thicker you would need skin thicker than a polar bear's to stay than a polar bear's to stay warm. warm.

Neptune and Uranus are very Neptune and Uranus are very much alike. They are both much alike. They are both large large gas planets that look planets that look like big blue-green balls in the like big blue-green balls in the sky. Neptune has winds in its sky. Neptune has winds in its atmosphere which blow at which blow at over 2000 kilometers per over 2000 kilometers per hour! This planet has large, hour! This planet has large, dark circles on its surface dark circles on its surface which astronomers believe to which astronomers believe to be storms. be storms.

Neptune has two thick and Neptune has two thick and two thin rings which surround two thin rings which surround it. Neptune also has thirteen it. Neptune also has thirteen known moons. Four of these known moons. Four of these moons orbit the planet within moons orbit the planet within the rings. One of Neptune's the rings. One of Neptune's moons, Triton, orbits the moons, Triton, orbits the planet in a direction opposite planet in a direction opposite to Neptune's other moons. to Neptune's other moons. Neptune is the farthest planet Neptune is the farthest planet from the Sun.from the Sun.