1. The Solar System Kayli White & Anne Riley

3. The inner planets vs. the outer planets The inner planets: Mercury, Venus, Earth, and Mars. They are relatively small, composed mostly of rock, and have few or no moons. The outer planets: Jupiter, Saturn, Uranus, Neptune, and Pluto. They are huge, mostly gaseous, ringed, and have many moons The exception is Pluto, the dwarf planet, which is small, rocky, and has one large moon plus two tiny ones.

4. Temperatures of the Planets Generally, the farther from the Sun, the cooler the planet. Differences occur when the greenhouse effect warms a planet (like Venus) surrounded by a thick atmosphere.

5. Density of the Planets The outer, gaseous planets are much less dense than the inner, rocky planets. The Earth is the densest planet. Saturn is the least dense planet; it would float on water.

6. A day on the Planets Compared to Earth A day is the length of time that it takes a planet to rotate on its axis (360°). A day on Earth takes almost 24 hours. The planet with the longest day is Venus. A day on Venus takes 243 Earth days. (A day on Venus is longer than its year; a year on Venus takes only 224.7 Earth days) The planet with the shortest day is Jupiter. A day on Jupiter only takes 9.8 Earth hours. VenusJupiter

8. Mercury Planet closest to the Sun Has no moons Dry, nearly airless, and full of craters Much like our moon Mercury's core is 75% of Mercury by volume and 80% of it by mass

9. Venus Second planet closest to the Sun Has no moons Atmosphere is 97% carbon dioxide It’s surface temperature is 480 °C (896 °F)

10. Earth Third planet from the Sun Has one moon Only planet capable of sustaining life Three distinct layers. The core is the central part made up of molten nickel and iron. The next layer is the mantle consisting of solid, hot rock. The crust upon which we walk and live is the upper- most layer, consisting of soil, clay, and fine rock.

11. Mars Fourth planet from the Sun Has 2 moons Has a reddish color due to the iron oxide (rust) that is in the soil Has the largest volcano Most Earth-like planet and may one day habitat humans

12. Jupiter Fifth planet from the Sun Has 18 large moons and many small ones About 1,320 Earths could fit inside of it Has faint ring system Great Red Spot: gigantic storm on Jupiter’s surface

13. Saturn Sixth planet from the Sun Has 18 large moons and many small ones Gas giant composed of hydrogen, with small proportions of helium. Has rings consisting mostly of ice particles Least dense planet

14. Uranus Seventh planet from the Sun Has 15 moons First planet to be discovered Has a system of about 11 rings Atmosphere composed of hydrogen, helium, methane, and ammonia

15. Neptune Eighth planet from the sun Has 2 moons Atmosphere composed of hydrogen, helium, methane, and ammonia Uranus’ twin Great Dark Spot: (left) a depression in the atmosphere surrounded by high cirrus clouds

16. Pluto Farthest planet from the Sun Has 1 large and 2 small moons Considered a dwarf planet Small, rocky

17. Space Probes A space vehicle carrying sophisticated instrumentation but no crew Goes around planets collecting information and pictures to help scientist understand the weather and changes that planets go through Unlike an artificial satellite, which is placed in a permanent orbit around the earth, a space probe is launched with enough energy to escape the gravitational field of the earth and navigate among the planets. Many do not return back to Earth