Bell work

1. Bell work • Create a new mnemonic device to help you remember the order of the planets: • My very excited mother just served us nectarines. • Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune • Record your mnemonic device in your science journal.

2. Inner Planets Mercury, Venus, Earth, and Mars

3. Objectives for today! • Explain the difference between a planet’s period of rotation and period of revolution. • Describe the difference between prograde and retrograde rotation. • Describe the individual characteristics of Mercury, Venus, Earth, and Mars. • Identify the characteristics that make Earth suitable for life.

4. Planets • Did you know that planets, when viewed from Earth, look like stars to the naked eye? • Ancient astronomers were intrigued by these "stars" which seemed to wander in the sky. • Ancient astronomers named these "stars" planets, which means "wanderers" in Greek. • These astronomers knew planets were physical bodies and could predict their motions.

5. Measuring distances in space • One astronomical unit (AU) is the average distance between the sun and Earth, or approximately 150,000,000 km. • Light year-this is the distance light travels in one year. Light travels at about 300,000 km/s in space. This means that in 1 s, light travels 300,000 km.

6. Inner Planets • The planets of the inner solar system are more closely spaced than the planets of the outer solar system. • The inner planets are also known as the terrestrial planets because their surfaces are dense and rocky.

7. Mercury • Distance from the Sun-3.2 light minutes • Period of rotation-58 Earth days, 19 h • Period of revolution-88 earth days • Gravity- 38% of Earth's • Temperature- −173ºC to 427ºC

8. Mercury • On Mercury you would weigh only 38% of what you weigh on Earth. • As you know, a year is the time that a planet takes to go around the sun once. • Every 88 Earth days, or 1.5 Mercurian days, Mercury revolves once around the sun.

9. Venus • Distance from Sun-6.0 light-minutes • Period of rotation-243 Earth days, 16 h (R)* • Period of revolution-224 Earth days, 17 h • Gravity-91% of Earth's • Temperature-464°C • *R = retrograde rotation

10. Venus is only slightly smaller, less massive, and less dense than Earth. • Venus and Earth rotate in opposite directions. Venus • Venus's atmosphere has 90 times the pressure of Earth's atmosphere! • The air on Venus is mostly carbon dioxide, but the air is also made of some of the most destructive acids known. • Venus has the hottest surface of any planet in the solar system.

11. Venus • Earth has a prograde rotationthe counterclockwise spin of a planet or moon as seen from above the planet’s North Pole; rotation in the same direction as the sun’s rotation • Venus has a retrograde rotationthe clockwise spin of a planet or moon as seen from above the planet’s North Pole

12. Objectives for today! • Explain the difference between a planet’s period of rotation and period of revolution. • Describe the difference between prograde and retrograde rotation. • Describe the individual characteristics of Mercury, Venus, Earth, and Mars. • Identify the characteristics that make Earth suitable for life.

13. Earth • Distance from Sun-8.3 light-minutes • Period of rotation- 23 h, 56 min • Period of revolution- 365 days, 6 h • Gravity-100% of Earths! • Temperature- −13°C to 37°C

14. Earth • Water on Earth • Earth formed at just the right distance from the sun. • Earth is warm enough to keep most of its water from freezing. • But unlike Venus, Earth is cool enough to keep its water from boiling away. • Liquid water is a vital part of the chemical processes that living things depend on for survival.

15. Mars • Distance from Sun-12.7 light-minutes • Period of rotation- • 24 h, 40 min • Period of revolution- • 1 year, 322 days • Gravity-38% of Earth's • Temperature- • −123°C to 37°C

16. Mars The Atmosphere of Mars • Mars has a thinner atmosphere and is further from the sun, making it a cold planet. • Midsummer temperatures recorded by the Mars Pathfinder range from –13°C to –77°C. • Martian air is so thin that the air pressure on the surface of Mars is about the same as it is 30 km above Earth's surface. • The air pressure is so low that any liquid water would quickly boil away. The only water found on the surface of Mars is in the form of ice. Water on Mars • Even though there is no liquid water on Mars's surface today, there is strong evidence that it existed there in the past. • There are areas on Mars with features that resemble a lake.

18. Mars Where Is the Water Now? • Mars has two polar icecaps- frozen water and frozen carbon dioxide. • The polar icecaps do not have enough water to create a thick atmosphere or rivers. • Scientists think that it is frozen beneath the Martian soil. Martian Volcanoes • Mars has only two large volcanic systems. • The largest, the Tharsis region, stretches 8,000 km across the planet. • The largest mountain in the solar system, Olympus Mons, is an extinct shield volcano. • Mars has a slightly different chemical makeup. This makeup may have kept the Martian crust from moving around as Earth's crust does. • As a result, the volcanoes kept building up in the same spots on Mars.

19. Objectives for today! • Explain the difference between a planet’s period of rotation and period of revolution. • Describe the difference between prograde and retrograde rotation. • Describe the individual characteristics of Mercury, Venus, Earth, and Mars. • Identify the characteristics that make Earth suitable for life.