17.1 Comparing size and distance The Sun is by far the largest object in the solar system. One astronomical unit (AU) is equal to 150 million km, or the distance from Earth to the Sun.

17.2 The planets The planets are commonly classified in two groups. The terrestrial planets include Mercury, Venus, Earth, and Mars. The gas giants include Jupiter, Saturn, Uranus, and Neptune.

Planet Activity Create a crossword puzzle with words describing a planet. Cross word puzzle must include 10 down and 10 across. Draw a cartoon to explain a planet. At least 10 frames, colored and neat. Create a mural or collage of a planet. Include a 2-paragraph explanation. Research a planet and make a diary of that experience as if you were there. Include location, type, and use your 5 senses. Create a children's book. Use your creativity. Must include pictures and basic story line Write a two-page paper that discusses the differences of two planets.

17.2 Mercury Mercury, the closest planet to the sun, is the second smallest (after Pluto) in both size and mass.

17.2 Venus Venus appears as the brightest planet in the evening sky and is the third brightest observable object (after the sun and moon).

17.2 Earth Earth is a small, rocky planet with an atmosphere that is made of mostly nitrogen (78 percent N 2 ) and oxygen (21 percent O 2 ).

17.2 Mars The fourth planet out from the sun, Mars appears as a reddish point of light in the night sky.

17.2 Jupiter The fifth planet out from the sun, Jupiter is by far the largest. Jupiter’s mass is greater than the combined mass of all of the other planets. With 63 known moons, Jupiter is like a mini solar system.

17.2 Saturn Saturn, at almost 10 times the size of Earth, is the second largest planet. The most striking feature of Saturn is its system of rings and like Jupiter, has many natural satellites.

17.2 Uranus The seventh planet from the sun, Uranus can barely be seen without a good telescope and was not discovered until 1781.

17.2 Neptune Neptune, the eighth planet from the sun, is the outermost of the gas planets. It was discovered in 1846 and its discovery almost doubled the diameter of the known solar system because of its great distance from the sun.

17.2 Comparing the planets