1. Touring our Solar System- Ch. 23
Ag. Earth Science
Ms. Weigel

2. 23.1 The Solar System

3. The Planets: An Overview
Two Groups of planets
Terrestrial Planets- Mercury, Venus, Earth and Mars- relatively small and rocky
Jovian Planets- Jupiter, Saturn, Uranus, and Neptune- are huge gas giants

4. The Planets: An Overview
3. Size is the most obvious difference between the terrestrial and Jovian Planet.
4. Density, chemical makeup and rate of rotation are other ways in which the two groups of planets differ.

5. Size and Scale

6. The Interiors of the Planets
The Substances that make up planets are divided into three groups: gases, rocks and ices.- Based on melting points
The gases-hydrogen and helium- melting points near 0 degree K or degrees C
The rocks- minerals and metallic iron- melting pt. 700 degree c
The ices- ammonia, methane, carbon dioxide and water- melting point 0 degree C
2. Terrestrial planets are dense, mostly rocky or metallic w/ minor ice
3. Jovian planets are less dense, largely gas and ice

7. The Atmospheres of the Planets
Jovian planets have thick atmospheres of hydrogen, helium, methane and ammonia
Terrestrial planets have meager atmospheres
The planets ability to retain atmosphere depends on its mass and temperature

8. Formation of the Solar System
A cloud of dust and gas in space is called a nebula
Nebular Theory
According to the nebular theory, the sun and planets formed form a rotating disk of dust and gases.
Matter became more concentrated in this center, where the sun eventually formed

9. Nebular Theory
Energy in stars combine. Heavier elements are formed when the star explodes
New particles bump into each other, clumping together like a snowball

10. Planetesimals
Growth of planets began as solid bits of matter colliding and clumping.
The colliding matter formed small, irregularly shaped bodies called planetesmials
The inner solar system, close to the sun, temperatures were so high that only metals could form solid grains.
In the frigid outer reaches, it was cold enough for ices of water and other substances to form.

11. The Terrestrial Planets
Section 23.2
The Terrestrial Planets

12. Mercury: The Innermost Planet
Innermost and smallest planet- hardly larger then earth’s moon.
Absorbs most of the sunlight that strikes it and reflects 6 percent back into space
Low reflections means that they have no atmosphere

13. Surface Features Cratered highlands like the moon
Smooth terrains like Maria
Very dense planet- large iron core
Long scarps (deep slopes) that cut across the plains and craters.

14. Surface Temperature
1. Revolves around the sun quickly but rotates slowly
One rotation takes 59 Earth-days
2. Night on Mercury lasts for about three months
3. Nighttime drop as low as -173 degrees C and noontime temp exceed 427 degrees C
Hot enough to melt lead
4. Mercury has the greatest temperature extremes of any planet

15. Check Point
How does Mercury’s period of rotation compare with Earths?

16. Venus: The Veiled Planet
Second to the moon in brilliance in the night sky
Orbits the sun once every 255 Earth-days
Near perfect circle
Similar density, mass and size to earth

17. Surface Features
Covered in thick clouds that visible light cannot penetrate
Data have confirmed that basaltic volcanism and tectonic activity shape Venus's surface.
Based on the low density of impact craters, these forces must have been very active during the recent geologic past.

18. Surface Temperature
Greenhouse gas effects het the atmosphere to 475 degree Celsius
Hot enough to melt lead
This heat is called the Venus runaway greenhouse effect
Atmosphere is 97 percent carbon dioxide, a greenhouse gas.
Scientists think oceans evaporated early in history, The vapor then accelerated the effect. Ultraviolet rays broke down the water.

19. Check Point
Describe the compositions of Venus's atmosphere

20. Mars: The Red Planet
Know as the red planet, it appears as a reddish ball when viewed through a telescope
Evoked greater interest than any other planet
Has dark regions during Martian year and some brilliant white polar caps

21. The Martian Atmosphere
Atmosphere has only 1 percent the density of Earth’s.
Though the atmosphere is very thin, extensive dust storms occur and may cause the color changes observed from Earth
Hurricane- force winds up to 270 kilometers per hour can persist for weeks

22. Surface Features
Mariner 9, the first space craft to orbit another planet, reached Mars in 1971
Most Martian surface features are old by Earth standards
Mar’s northern hemisphere revealed numerous large volcanoes
The biggest, Olympus Mons, is the size of Ohio and is 23 kilometers high. Over two and a half times higher than mount Everest.
Mars also has several canyons, much larger than Earth’s Grand Canyon

23. Water On Mars
Some areas of Mars revealed drainage patterns similar to those created by streams on Earth
Images from the Mars Global Surveyor indicate groundwater has recently migrated to the surface.
Some escaping water may have been frozen due to Martian temperatures range between -70degrees C and -100 degrees C.

24. Critical Thinking
Besides Earth, which inner planet may have been most able to support life?
Why are surface temperatures so high on Venus?

25. Writing in science
A space mission to the moon or Mars often costs millions of dollars. Yet it is hoped that space exploration can give us valuable knowledge about the solar system. Consider pros & cons of space exploration.

26. Ch The Outer Planets

27. Jupiter: Giant Among Planets
Jupiter has a mass that is 2 ½ times greater than the mass of all the other planets and moons combined.
When view through a telescope Jupiter appears to be covered with alternating bands of multicolored clouds that run parallel to its equator.

28. Structure of Jupiter Atmosphere is hydrogen-helium
Small amounts of methane, ammonia, water and sulfur
The wind systems generate light and dark colored bands that encircle the planet
Wind on Jupiter gives off twice as much heat as it receives from the sun
Jupiter is thought to be a gigantic ocean of liquid hydrogen.

29. Jupiter’s Moons The satellite system consists of 28 moons
4 largest discovered by Galileo
1979 revealed photos of the first four
The inner most, Io, is one of three known volcanically active bodies in our solar system
Others are earth and Neptune's moon Triton

30. Checkpoint
Which Galilean moon is volcanically activie?

31. Jupiter’s Moons

32. Jupiter’s Rings Voyager 1 discovered Jupiter's ring system
The faint nature of the rings indicates these fragments were widely dispersed.

33. Saturn: The Elegant Planet
29.46 Earth-years to make on revolution, Saturn is almost twice as far from the sun as Jupiter.
Though they still have similar atmospheres
The most prominent feature of Saturn is its system of rings
1610 Galileo used a primitive telescope and first saw the rings

34. Features of Saturn
Saturn’s atmosphere is very active, with winds up to kilometers per hour.
Large cyclonic “storms” similar to Jupiter's great red spot
Rings were found to be more complex

35. Saturn’s Rings
Until the discovery of Jupiter, Uranus and Neptune's rings, Saturn was thought to be the only one.
Each ring is composed of individual particles- “moonlet’ of ice and rock that circle the planet while regularly impacting on another

36. Saturn’s Moons Saturn’s satellite system consists of 31 moons
Titan is the largest moon and is bigger then Mercury.
Second largest in the solar system
Titan and Neptune’s Triton are the only mons in the solar system known to have substantial atmospheres

37. Checkpoint
How many moons of Saturn have been discovered thus far?

38. Uranus: The Sideways Planet
A unique feature of Uranus is that it rotates “on its side”
Instead of being generally perpendicular to the plane of its orbit like the other planets, Uranus’s axis of rotation lies nearly parallel with the plane of its orbit.
It’s rotational motion, has the appearance of rolling, rather than top like spinning

39. Checkpoint
What is unique about Uranus’s axis of rotation?

40. Neptune: the Windy Planet
Winds exceeding 1000 kilometers per hour encircle Neptune, making it one of the windiest places in the solar system.
Neptune has 13 moons and ring system
Triton, Neptune’s largest moon, is nearly the size of Earth’s moon.

41. Pluto: Planet X
Pluto lies on the fringe of the solar system, almost 40 times farther from the sun than Earth.
It is 10,000 times too dim to be visible to the unaided eye.
Pluto’s orbit is highly eccentric, causing it to occasionally travel inside the orbit of Neptune, Where it resided in 1979
Some astronomers think Pluto should be considered a minor planet due to its small size and location within a swarm of similar icy objects, others disagree

42. 23.4 Minor Members of the Solar System

43. Asteroids: Microplanets
Asteroids- small rocky bodies that have been likened to “flying mountains”
Largest, ceres, is 1000 kilometers in diameter
Most asteroids lie between the orbits of Mars and Jupiter.
The orbital periods of three to six years
They are irregularly shaped
Eccentric orbits, travel near to the sun and a few larger ones regularly pass close to Earth and the moon

45. Checkpoint
What is an asteroid?

46. Comets
Comets- pieces of rocky and metallic materials held together by frozen gases such as water, ammonia, methane, carbon dioxide and carbon monoxide.
Many travel far beyond Pluto take thousands of years to orbit
A few have period of less than 200 years and encounter inner solar system

47. Coma
When a comet first appears it is very small, but as it approaches the sun, solar energy begins to vaporize the frozen gases- the glowing head is called a coma
As comets approach the sun, some, but not all, develop a tail that extends for millions of kilometers.
The tail of a comet points away from the sun in a slightly curved manner.
Comets move away from the sun- as gases are expelled and the they begin to disappear they continue the orbit without a coma or a tail.

48. Checkpoint
In which direction does the tail of a comet point?

49. Kuiper Belt Comets originate in two regions of the outer solar system
Those with short orbital periods are thought to orbit beyond Neptune in a region called the Kuiper belt.
Kuiper belt comets move in nearly circular orbits that lie roughly in the same plane as the planets

50. Oort Cloud
These comets appear to be distributed in al directions, forming a spherical shell around eh solar system
Only a tiny portion of the Oort cloud comets pass into the inner solar system

51. Halley’s Comet Most famous short- period comet
Orbital period every 76 years
Predicted next perihelion: July 28, 2061
Gases and dust that vaporizes from the nucleus to form the coma and tail appear to gush as bright jet streams.

52. Meteoroids
Meteorite- a meteoroid that actually reaches the Erath’s surface
This created craters

53. Meteorites and the Age of the Solar System
Scientist determined the age of the solar system by using evidence from meteorites, mon rocks and earth rocks.
Radiometric dating shows the oldest meteorites formed than 4.54 billion years ago.
Oldest moon rocks about 4.6 billion years old
Oldest earth rocks found in Australia are 4.3 billion years old