Components of our solar system
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The Terrestrial PlanetsThere are four terrestrial planets, each small and dense with rocky surfaces: Mercury, Venus, Earth, and Mars.
MercuryMercury is the smallest of the four, and closest to the sun. Mercury has many flat plains and craters. Mercury has no atmosphere. Due to Mercury's small size, its gravity is weak and heated gas particles can easily escape. Its temperature ranges from 430 degrees Celsius to -170 degrees Celsius when it is not facing the sun.
VenusVenus is similar to Earth in density and internal structure. Strangely, a day on Venus is longer than its year. Venus rotates from esat to west, opposite from other planets. Venus's atmosphere is extremely thick with clouds made of sulfuric acid. Its average surface temperature is 460 degrees Celsius.
EarthEarth has a crust, mantle and core. Earth is the only planet in our solar system to have liquid water at its surface. Earth has enough gravity to gold on to most gases, making up Earth's atmosphere. Only Earth's atmosphere is rich in oxygen.
MarsMars has its color from rusty dust that covers its surface. Mars's atmosphere has more than 95% carbon dioxide. You could walk around on Mars with an airtight suit and oxygen. Temperatures range from -140 to 20 degrees Celsius. Scientists think that liquid water once flowed on Mars's surface in the past. Mars has two polar ice caps containing frozen water and carbon dioxide.
The Gas GiantsThere are four gas giants, each with many moons, rings, and no solid surfaces: Jupiter, Saturn, Uranus, and Neptune.
JupiterJupiter is the largest planet, 2.5 times the mass of all the other planets combined. Jupiter has a thick atmosphere of hydrogen and helium. The Great Red Spot is a hurricane larger than Earth. Jupiter has dozens of moons.
SaturnSaturn is the second largest planet in the solar system. Saturn has a thick atmosphere of hydrogen and helium. Oddly, Saturn is the only planet with an average density less than water. Its rings are the most spectacular, made of chunks of ice and rock, orbiting around Saturn.
UranusUranus is four times the diameter of Earth, but significantly smaller than Saturn. Uranus is much colder and is blue-green due to traces of methane. Uranus has thin, flat rings. Uranus's axis of rotation is at an angle of 90 degrees from vertical. This means Uranus rotates on its side, viewed from Earth.
NeptuneNeptune has the same size and color as Uranus. Neptune is a cold, blue planet with its atmosphere containing visible clouds. Neptune was discovered as a result of a mathematical prediction. Neptune has at least thirteen moons orbiting Neptune.
Space RocksThere are three main types of space rocks: Comets, Asteroids, and Meteors.
CometsComets are collections of ice, dust, and small rocky particles whose orbits are usually long, narrow ellipses.The energy in the sunlight turns the ice itno gas releasing dust when a comet gets close enough tot he sun. A fuzzy outer layer is formed, called a coma. The nucleus is the solid inner core of a comet. Some of the gas forms a tail, pointing directly away from the sun. Most comets come from the Kuiper Belt or the Oort cloud.
AsteroidsAsteroids are rocky objects that revolve around the sun between Mars and Jupiter. Most asteroids are very small, and are not considered planets. Scientists hypothesize that asteroids are the leftover pieces that never formed a planet. Someday, an asteroid could hit the Earth, leading to extinction as it once did to the dinosaurs.
MeteorsMeteors are meteoroids, are chunks of rock or dust from comets or asteroids, that enter the Earth's atmosphere. Some form when asteroids collide in space or whena comet breaks up. When a meteoroid enters Earth's atmosphere, friction creates heat and a streak of light in the sky. Meteorites are meteoroids that pass through the atmosphere and strike Earth's surface.