The Physical Universe, 11/e: The Physical Universe, 11/e Konrad B. Krauskopf, Prof. Emeritus of Geochemistry, Stanford Univ. Arthur Beiser ISBN: 0072418265 Copyright year: 2004


Chapter 16 The Solar System: Chapter 16 The Solar System


The Solar System: Main Ideas: The Solar System: Main Ideas Our solar system The sun and planets Comets and meteors The inner planets The outer Planets The Earth’s Moon


General overview of our solar system: General overview of our solar system Our solar system is composed of the Sun, nine planets and their satellites. Along with smaller bodies such as asteroids. The nine planets are Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto


Other parts of the solar system: Other parts of the solar system A band of asteroids, all of which are less than 1000km in diameter (much smaller than any planet) also orbit about our sun in a broad band between Jupiter and Mars Most of the planets has one or more satellites, called MOONS Each planet in our solar system has now been observed by spacecraft launched from earth


The inner planets: The inner planets The “Inner planets” is the term coined for the four planets closest to the sun: Mercury, Venus Earth, Mars These relatively small planets have similar compositions and densities Most are composed of rocky material Most have cores that are likely iron There are only three satellites on these four planets The Earth’s moon is the largest Mars has two small moons


The Outer Planets: The Outer Planets Four of the outer planets, Jupiter, Saturn, Uranus and Neptune are very large, but have much smaller densities when compared to the inner planets These planets are composed mostly of gas, with cores of liquid Among these four planets there are over 130 satellites They rotate rapidly on their axes


Fig. 16-1 Our solar system: Fig. 16-1 Our solar system


Fig 16-2 Planet size: Fig 16-2 Planet size


Similarities in Motion: Similarities in Motion The orbital direction and rotation directions are the same for all the planets, with the exception of Venus All orbits except Pluto lie in very nearly the same plane Pluto is an exception, since it is very far away, and its orbit is unusual compared with the other planets


Fig. 16-3: the orbital planes: Fig. 16-3: the orbital planes A side view of our solar system reveals that nearly all of the planetary orbits lie in the same plane (except Pluto)


Comets and Meteors: Comets and Meteors Comets and meteors are debris from space Some of these traveling bodies have become trapped in the gravitational field of the sun Comets are characterized by the tail of gas and dust that trails behind them The direction of the tail always points away from the sun Comet tails may stretch for thousands of miles Meteors are small fragments of matter When meteors reach the earth’s atmosphere they can burn up IF the mass makes it to the surface of the earth, it is called a meteorite


Meteorites: Meteorites Scientists are interested in studying meteorites because they contain clues to the composition of other bodies in the universe Meteorites are of two main types Stony meteorites Iron meteorites


Inner planet: Mercury: Inner planet: Mercury Named the Greek messenger god When visible, Mercury always lies near the sun Most visible at sunset or sunrise Mercury facts 59 day rotational period 88 day orbital period (year) A day on Mercury is like 176 Earth Days Very high surface temperatures (>425C) Explored by Mariner 10


Inner Planet: Venus: Inner Planet: Venus Named for the Roman goddess of love Venus is the brightest object in the night sky (except for sun or moon) Like Mercury, Venus is always seen near the sun Venus has a rotational direction opposite from all the other planets Venus is closer in size or mass to Earth than any of the other planets Venus even has geographical features similar to those of the earth The atmosphere of Venus is very different from earth; it is dense and mostly carbon dioxide


Inner Planet: Mars: Inner Planet: Mars Mars is named for the Roman god of war Based on its typical red-orange appearance Mars has two satellites which are very small in comparison to Earth’s moon Mars is of current scientific interest due to the exploration of the surface by the remote robotic landers, Spirit and Opportunity


Exploring Mars: Exploring Mars Much of the excitement that fueled exploration of the Martian surface was the possibility of finding evidence of life on Mars One of the biggest questions being addressed by Spirit and Opportunity is that of the presence of water Frozen water is know to exist The question is: was this water ever in liquid form? So far, most of the evidence collected by previous missions has not supported the idea of liquid water or life on Mars


The Asteroid Belt: The Asteroid Belt The largest asteroid known is about 1000km across There are several thousand in number, with most being less than 100km across Some of the asteroids pass within the Earth’s orbit from time to time Even though they are small in comparison to earth, they are moving at high speeds Small asteroids do not pose a threat A very large asteroid impact could be devastating


An Asteroid Collision: An Asteroid Collision Scientists track the paths of larger asteroids One large asteroid Mass about 2.2 billion tons Will pass near the earth on August 7, 2027 It will be as close to the earth as the Moon Scientists and engineers have explored ways in which a near-miss with a large asteroid or its debris could be avoided with the use of large scale explosives


Outer Planet: Jupiter: Outer Planet: Jupiter Jupiter, the largest planet in our solar system, was named after the king of the Roman gods It is striated in appearance, with a large marking called “the Great Red Spot” as large as two earths seen on its surface Jupiter has 61+ known satellites Jupiter is a low density planet, consisting of mostly hydrogen and helium


Outer planet: Saturn: Outer planet: Saturn Saturn is well known for its beautiful rings Saturn was named after the Roman god who was the father of Jupiter It’s structure is similar to Jupiter, but much smaller Saturn has at least 39+ satellites Saturn’s rings are actually a collection of small particles orbiting Saturn Not gas or solid


Uranus, Neptune, Pluto: Uranus, Neptune, Pluto These outermost planets were not discovered until the advent of telescopes While Neptune and Uranus are similar, Pluto is oddly different Although Pluto is thought to have a satellite, Charon, and possibly two more moons.


Important notes about the planets: Important notes about the planets None of the planets produce light They are only visible due to light reflected from the sun


The Earth’s Moon: The Earth’s Moon Like the planets, the moon reflects light from the sun The average Earth-Sun distance is 384,400km or 240,000 miles away The diameter of the moon is roughly ¼ that of the Earth The moon orbits the earth once every 27½ days (relative to the stars) The moon does spin on its axis as it orbits; the same side of the moon is always facing the earth


Phases of the Moon: Phases of the Moon WE are all familiar with the phases of the moon This refers to the portion of the illuminated moon that we view at certain times during each lunar cycle The moon’s shape changes from a thin crescent to a full circle and then back again When the illumined portion appears to be growing larger, we say the moon is waxing When the illuminated portion appears to getting smaller, we say that the moon is waning


Lunar and Solar Eclipses: Lunar and Solar Eclipses Sometimes the positions of the sun, earth and moon are such that light from the sun is occluded by either the moon or the earth These events do not occur often, since it requires that the orbital planes of the earth-moon system be aligned with the earth-sun system


Eclipse: Eclipse When the position of the Earth prevents a portion of the sunlight from hitting the moon it is called a LUNAR ECLIPSE When the position of the Moon prevents a portion of the sunlight from hitting the earth, it is called a SOLAR ECLIPSE Total eclipse happens only when there is complete alignment between all three bodies Table 16-5 lists expected eclipse events


Fig. 16-36: Lunar and Solar Eclipse: Fig. 16-36: Lunar and Solar Eclipse In this figure, we see how the shadows cast by the earth and moon cause eclipses


The Lunar Surface: The Lunar Surface Scientists know a great deal about the landscape of the moon July 20, 1969 marked the first landing of a human craft on our Moon Neil Armstrong was the first person to ever set foot on our moon From this and other lunar missions a great deal of lunar material has been returned to the earth for study


The Lunar Landscape: The Lunar Landscape The lunar surface consists of two main features Dark, smooth MARIA Rugged mountain highlands Scientists once thought that water might exist on the moon, but those ideas have since been discounted Scientists have learned much about the history of the Moon from studying the lunar landscape, but also from direct examination of soil and rock samples


History of the Moon: History of the Moon The picture of the Moon’s history is more complete than that of the Earth due to the absence of weathering on the moon The moon is old, with the youngest rocks being dated at over 3 billion years old This means that all igneous activity ceased prior to this point While the formative processes of the materials on the moon may have been much like those still occurring on Earth, they have since stopped, leaving the moon in a static state for a very long time, being changed only by meteorite bombardment


Origin of the Moon: Origin of the Moon When trying to understand how the moon may have come to orbit the Earth, scientists initially proposed three likely scenarios 1. The moon was a part of the earth that split off to become an orbiting satellite 2. The moon was formed elsewhere and was later captured by the earth’s gravitational field 3. the moon and earth were once a double planet system


Figure 16-43: origin of the moon: Figure 16-43: origin of the moon


Another idea: Another idea Today, the most widely accepted idea about the origin of the moon is known as the COLLISION HYPOTHESIS In this theory, it is proposed that a small planet collided with the earth, creating debris from both planets that formed the moon In this picture, the core of the small colliding planet was added to that of the earth This means that the earth was changed dramatically in the process of forming the moon


The Solar System: Summary: The Solar System: Summary Comets and meteoroids: small objects that have established, regular orbits in our solar system Meteors can be seen as they enter earth’s atmosphere There are nine planets in our solar system: Mercury, Venus, Earth, Mars (known as the inner planets) Jupiter, Saturn, Uranus, Neptune (called the outer planets) And Pluto An asteroid belt lies between Mars and Jupiter The moon and all the planets are visible due to reflection of light from the sun


The Solar System: Summary (2): The Solar System: Summary (2) The moon undergoes PHASES due to the relative positions of the earth-moon-sun system A lunar eclipse is when the shadow of the earth falls on the sun A solar eclipse is when the shadow of the moon falls on the earth Much has been learned about the environment on the moon due to manned and un-manned lunar exploration


IN-LECTURE QUIZ QUESTIONS CHAPTER 16: IN-LECTURE QUIZ QUESTIONS CHAPTER 16


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 Comets are primarily composed of A. hydrogen B. ice and dust C. helium B. iron


IN-LECTURE QUIZ CHAPTER 16 : IN-LECTURE QUIZ CHAPTER 16 Planets are visible in the night sky because A. Planets emit light in the visible region of the spectrum B. Planets reflect light from the sun C. Planets reflect light from the other stars in the universe D. Planets reflect light from the earth’s moon


IN-LECTURE QUIZ CHAPTER 16 : IN-LECTURE QUIZ CHAPTER 16 The closest planet to the sun is A. Earth B. Jupiter C. Venus D. Mercury


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 True or False There is a part of the moon that is never illuminated by the sun.


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 The brightest planet in the night sky is A. Venus B. Mars C. Jupiter D. Saturn


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 One of the planets has no known satellites. This planet is A. Venus B. Jupiter C. Saturn D. Uranus


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 True or False There is strong evidence that water has existed on the surface of the moon


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 Why is it easier to compose a geologic history of the moon than it is to do the same for the earth? A. the moon has less history B. the moon has no atmosphere, so no weathering has occurred to complicate the geologic record C. the moon is formed from simpler materials and has a simpler fossil record D. moon core samples are easier to retrieve


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 The largest known asteroid is about A. 100 km in diameter B. 1000 km in diameter C. 1 km in diameter D. 1000 m in diameter


IN-LECTURE QUIZ CHAPTER 16: IN-LECTURE QUIZ CHAPTER 16 The largest planet in our solar system is A. Mars B. Saturn C. Jupiter D. Earth