PLANETS IN OUR SOLAR SYSTEM Terrestrial planets are Earth-like planets (in Latin, terra means Earth) made up of rocks or metals with a hard surface —

SOLAR SYSTEM

PLANETS IN OUR SOLAR SYSTEM

Terrestrial planets are Earth-like planets (in Latin, terra means Earth) made up of rocks or metals with a hard surface — making them different from other planets that lack a solid surface. Terrestrial planets also have a molten heavy metal core, few moons, and a variety of topological features like valleys, volcanoes and craters. In our solar system, there are four terrestrial planets, which also happen to be the four closest to the sun: Mercury, Venus Earth and Mars.

INNER PLANETS

In the outer Solar System are the four remaining planets Jupiter, Saturn, Uranus, and Neptune. Made primarily of gasses these planets are called gas giants. Gas giants are massive and consist of a thick atmosphere and a dense molten core. Because the gas giants aren't made of rock and solid matter they don't have solid surfaces like the terrestrial planets. Therefore landing on one would be impossible.

OUTER PLANETS

ROTATION

REVOLUTION

Jupiter’s Moons

The planet Jupiter's four largest moons are called the Galilean satellites, after Italian astronomer Galileo Galilei, who observed them in 1610. These large moons, named Io,  Europa, Ganymede, and Callisto, are each distinctive worlds.

Io is the most volcanically active body in the solar system.

Io's surface is covered by sulfur in different colorful forms.

As Io travels in its slightly elliptical orbit. Jupiter's immense gravity causes "tides" in

the solid surface that rise 100 m (300 feet) high on Io, generating enough heat for volcanic activity and to drive off any water. Io's volcanoes are driven by hot silicate magma.

IO

Europa's surface is mostly water ice, and there is evidence that it may be covering an ocean of water or slushy ice beneath.

Europa

Europa is thought to have twice as much water as does Earth. This moon intrigues astrobiologists because of its potential for having a "habitable zone." Life forms have been found thriving near subterranean volcanoes on Earth and in other extreme locations that may be analogues to what may exist on Europa.

GANYMEDE

Ganymede is the largest moon in the solar system (larger than the planet Mercury), and is the only moon known to have its own internally generated magnetic field.

Callisto's surface is extremely heavily cratered and ancient -- a visible record of events from the early history of the solar system. However, the very few small craters on Callisto indicate a small degree of current surface activity.

CALLISTO

GALILEAN MOONSJupiter's four largest moons are called the Galilean

satellites

GAS GIANTSThe four gas giants are (in order of distance from the Sun): Jupiter, Saturn, Uranus, and Neptune

• Asteroids are rocky, airless worlds that orbit our sun, but are too small to be called planets.

• Most Asteroids orbit our sun, a star, in a region of space between the orbits of Mars and Jupiter known as the Asteroid Belt.

• Asteroids are solid, rocky and irregular bodies.

ASTEROIDS

If all of the asteroids were combined into a ball, they would still be much smaller than Earth's moon. If the sun were as tall as a typical front door, Earth would be the size of a nickel, the moon would be about as big as a green pea and Ceres (the largest object in the main asteroid belt) would be as small as a sesame seed.

Comets are cosmic snowballs of frozen gases, rock and dust roughly the size of a small town. When a comet's orbit brings it close to the sun, it heats up and spews dust and gases into a giant glowing head larger than most planets. The dust and gases form a tail that stretches away from the sun for millions of kilometers.

COMETS

Comet Giacobini-ZinnerNASA

Little chunks of rock and debris in space are called meteoroids. They become meteors -- or shooting stars -- when they fall through a planet's atmosphere; leaving a bright trail as they are heated to incandescence by the friction of the atmosphere. Pieces that survive the journey and hit the ground are called meteorites.

METEORS

Meteorites may vary in size from tiny grains to large boulders. One of the largest meteorite found on Earth is the Hoba meteorite from southwest Africa, which weighs roughly 54,000 kg (119,000 pounds).

The Kuiper Belt is a disc-shaped region of icy objects beyond the orbit of Neptune -- billions of kilometers from our sun. Pluto and Eris are the best known of these icy worlds. There may be hundreds more of these ice dwarfs out there. The Kuiper Belt and even more distant Oort Cloud are believed to be the home of comets that orbit our sun.

Kuiper Belt & Oort Cloud: Overview

A gas giant, also known as a jovian planet after the planet Jupiter, gaseous giant, or giant planet, is a large planet which has at least ten times the mass of Earth, located in the outer solar system.

Unlike terrestrial planets whose composition is rocky, gas giants have a mostly gaseous composition, such as hydrogen and helium. They do have some rocky material, although this is most often found in the planet core.

their composition differs from Jupiter and Saturn. This is because they are mostly composed of water, ammonia, and methane.

GAS GIANTS