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

23.1 The Solar System

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

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.

Size and Scale

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 -273 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

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

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

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

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.

The Terrestrial Planets Section 23.2 The Terrestrial Planets

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

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.

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

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

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

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.

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.

Check Point Describe the compositions of Venus's atmosphere

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

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

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

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.

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

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.

Ch. 23.3 The Outer Planets

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.

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.

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

Checkpoint Which Galilean moon is volcanically activie?

Jupiter’s Moons

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

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

Features of Saturn Saturn’s atmosphere is very active, with winds up to 1500 kilometers per hour. Large cyclonic “storms” similar to Jupiter's great red spot Rings were found to be more complex

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

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

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

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

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

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.

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

23.4 Minor Members of the Solar System

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

Checkpoint What is an asteroid?

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

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.

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

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

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

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.

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

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