1	Nine Planets A Write On Activity
2	In this activity you will: Learn about the solar system. Practice your knowledge in an interactive game. Select one planet and write a paragraph containing four facts you learned.
3	Mercury Mercury is the closest planet to the Sun and the eighth largest planet. It has been visited by only one spacecraft, Mariner 10. Temperatures vary greatly on Mercury from 90 K to 700 K.
4	Mercury Mercury is similar to the Moon in that its surface is heavily cratered and very old. Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind.
5	Mercury Mercury has no known satellites.
6	Venus Venus is the second planet from the Sun and the sixth largest. Venus has been known since prehistoric times. It is the brightest object in the sky except for the Sun and the Moon. Its surface is actually hotter than Mercury's despite being nearly twice as far from the Sun.
7	Venus Venus is sometimes regarded as Earth's sister planet. Venus is only slightly smaller than Earth Both have few craters.
8	Venus Venus’ core is similar to that of Earth, an iron core. It has no satellites. It is called the "morning star" or the "evening star.”
9	Venus
10	Earth The Earth is the third planet from the Sun and the fifth largest planet. The Earth is divided into 3 main layers: The Crust The Mantle The Core
11	Earth The crust is thinner under the oceans, but thicker under the continents. Most of the mass of the Earth is in the mantle. The core is probably composed mostly of iron. 71 Percent of the Earth's surface is covered with water. It is the only planet on which water can exist in liquid form on the surface.
12	Earth Earth has only one natural satellite, the Moon.
13	Mars Mars is the fourth planet from the Sun and the seventh largest. Mars has been known since prehistoric times. The first spacecraft to visit Mars was Mariner 4 in 1965, but several others followed.
14	Mars Mars has the most highly varied and interesting terrain of any of the planets. There is evidence of erosion in many places on Mars including large floods and small river systems (right).
15	Mars Mars has permanent ice caps at both poles.
16	Jupiter Jupiter is the fifth planet from the Sun and the largest. It was first visited by the Pioneer 10 spacecraft in 1973. Jupiter is a gas planets and does not have a solid surface. Its core is composed of rocky material.
17	Jupiter The main bulk of the planet is in the form of liquid metallic hydrogen. The outermost layer is composed of ordinary molecular hydrogen and helium. The vivid colors seen in Jupiter's clouds are probably the result of chemical reactions in Jupiter's atmosphere.
18	Jupiter The Great Red Spot is caused by a high-pressure region whose cloud tops are significantly higher and colder than the surrounding regions.
19	Saturn Saturn is the sixth planet from the Sun and the second largest. Galileo was the first to observe it with a telescope in 1610. Like Jupiter, Saturn is a gas planet, about 75% hydrogen and 25% helium. Saturn's rings, unlike the rings of the other planets, are very bright.
20	Saturn The rings are actually composed of small particles each in an independent orbit. The thin ring particles seem to be composed primarily of water ice. Saturn has 18 named satellites plus 13 recently discovered.
21	Saturn
22	Uranus Uranus is the seventh planet from the Sun and the third largest (by diameter). Uranus, the first planet discovered in modern times on March 13, 1781. Uranus has been visited by only one spacecraft, Voyager 2 on Jan 24 1986.
23	Uranus Uranus is composed primarily of rock and various ices. Like the other gas planets, Uranus has bands of clouds that blow around rapidly. Uranus has rings composed of fairly large particles.
24	Uranus Voyager 2 discovered 10 small moons in addition to the 5 large ones already known.
25	Neptune Neptune is the eighth planet from the Sun and the fourth largest (by diameter). Neptune has been visited by only one spacecraft, Voyager 2 on Aug 25 1989. Neptune's composition is probably various "ices" and rock.
26	Neptune Being a gas planet, Neptune has rapid winds and large storms. Neptune has an internal heat source, radiating more than twice as much energy as it receives from the Sun. Neptune's most prominent feature is the Great Dark Spot.
27	Neptune Neptune has dark rings of an unknown composition. It has 11 known moons.
28	Pluto Pluto is the farthest planet from the Sun (usually) and the smallest. It was discovered in 1930. Pluto is the only planet that has not been visited by a spacecraft. Pluto has a satellite, Charon.
29	Pluto Some think Pluto would be better classified as a large asteroid or comet rather than as a planet. Pluto rotates in the opposite direction from most of the other planets. The surface temperature on Pluto varies between about -235 and -210 C.
30	Pluto Little is known about Pluto's atmosphere.
31	Can you match the planet and facts? Discovered in 1930 Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
32	Can you match the planet and facts? Has 3 main layers Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
33	Can you match the planet and facts? Closest to the sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
34	Can you match the planet and facts? Brightest planet in the sky Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
35	Can you match the planet and facts? Was first observed by Galileo Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
36	Can you match the planet and facts? The first planet discovered in modern times Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
37	Can you match the planet and facts? Has a Great Dark Spot Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
38	Can you match the planet and facts? Has permanent ice caps at both poles Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
39	Can you match the planet and facts? The largest planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
40	Writing Activity Choose one planet and create a paragraph about it using 4 facts you learned. Review the planets by clicking the name on the right.