Solar System Tour Page 1 of 10

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1 Solar System I. Origin of Solar System A. Nebular cloud of swirling gases and dust B. Composed mainly of hydrogen C. Gravitational collapse heated to fusion at center 1. material with high melting temperatures a. condensed in inner warm regions b. silica, metal c. accreted into inner rocky planets 2. material with low melting temperatures a. stayed melted in inner regions, condensed in outer regions b. methane, water, ammonia, carbon dioxide 1) lots of this stuff 2) became primordial outer large planets 3) large size has large gravitational field to hold light atoms a) hydrogen and helium b) gas giants II. Overview of the solar system Solar system includes A. Sun % of system mass 2. Nuclear fusion of hydrogen into helium B. Objects in orbit around Sun 1. Inner terrestrial planets a. Mercury, Venus, Earth, Mars b. Small, stony, Little atmosphere 2. Outer gas planets a. Jupiter, Saturn, Uranus, Neptune b. Large, Gases (hydrogen and helium) and ices (methane, ammonia) 3. Dwarf planets, asteroids, comets, meteoroids a. Various compositions 1) Terrestrial material, 2) ices b. various locations and orbits 1) asteroid belt in planetary plane of orbit c. highly eccentric and inclined orbits compared to eight planets III. Composition of Solar System objects A. Gases low melting temperature: about absolute zero 1. hydrogen most abundant gas in solar system 2. helium B. Rocky and metallic material high melting temperature: +700 o C 1. silicate minerals like igneous rocks 2. pure metals and alloys mostly iron and nickel C. ices (of things besides water) intermediate melting temperature 1. Ammonia (NH 3 ) 2. Methane (CH 4 ) Solar System Tour Page 1 of 10

2 3. Carbon dioxide (CO 2 ) 4. Water (H 2 O) D. Nebular cloud hypothesis of Solar System formation explains why inner planets and outer planets are different: temperatures and melting temperatures IV. Moon A. Earth s only natural satellite 1. Large in reference to Earth, compared to other natural satellites a. about ¼ of Earth s diameter b km 2. Density similar to Earth s mantle material, small iron core B. Surface not protected by atmosphere 1. Craters a. impact of meteoroids 1) ejecta 2) rays b. more common in early part of Moon s history 2. lunar highlands most of Moon s surface, all of back side a. low-iron content compared to maria b. original surface: intensely cratered 3. maria plural of mare a. high iron content lowlands b. younger than lunar highlands c. created by impact of large asteroids 1) caused sub-crustal melting 2) resulted in basalt flows similar to Columbia Plateau basalts 4. lunar regolith a. soil-like surface produced by numerous meteoroid impacts b. fine dust, glass beads, breccia, igneous rock V. Lunar history A. Earth impacted by large asteroid about 4.5 billion years ago 1. Caused part of Earth to be ejected into orbit around Earth 2. Dust accreted into lunar body a. Gravitational contraction caused melting and formation of crust, mantle and core. b. original surface was the present lunar highlands B. Maria basins formed 3.8 to 3.2 billion years ago by asteroid impact C. Continued bombardment created craters, including the rayed craters such as the Copernican crater Solar System Tour Page 2 of 10

3 VI. Planetary information A. Mercury 1.Innermost planet 2.smallest planet 4880 km diameter 3.orbit a. inclined 7 o to Sun s equator b. highly eccentric 45 million km to 70 million km c. Revolves quickly Orbital period 88 Earth days d. Rotates slowly 3 rotations in 2 orbits 1) 179 Earth days for one Mercury mean solar day 2) Table 21.1 says 59 days that s a sidereal day WHAT S THAT? 4.No atmosphere but trace of hydrogen and helium 5.Surface a. cratered highlands and vast, smooth terrains b. scarps suggest crustal shortening c. Extreme temperatures 1) Cold nights (-173 C, -280 F) 2) Hot days (427 C, 800 F) 6. Very dense large iron core 7.Mariner 10 photo mosaic 1974 went to Venus first B. Venus 1.motion a. Orbit 225 days (text citation is in error) b. Rotation is 243 Earth days, and retrograde (turns backwards) c. Axial tilt 2 o (178 0 retrograde) 2.Similar to Earth a. Size km (c.f km) b. Density and composition 1) 3000 km diameter iron core, 2) partly molten rocky mantle c. Location in the solar system d. Has atmosphere unlike Mars and Mercury 3.Shrouded in thick clouds a. Impenetrable by visible light b. Atmosphere is 97% carbon dioxide, 3% N 2, trace H 2 O c. Surface atmospheric pressure is 90 times that of Earth's 4.Surface a. Mapped by radar by Magellan Project b. Features 1) 80% of surface is subdued plains covered by volcanic flows 2) Low density of impact craters 3) Tectonic deformation must have been active during the recent geologic past 4) Thousands of volcanic structures Solar System Tour Page 3 of 10

4 C. Mars 1.Called the "Red Planet" telecscopic surface close enough to view, and clear enough to see 2.Atmosphere a. 1% as dense as Earth's b. Primarily carbon dioxide 95%, 3% N 2, 1.6% Ar, trace H 2 O c. Cold polar temperatures (-193 F) d. Polar caps of water ice, covered by a thin layer of frozen carbon dioxide e. Extensive dust storms with winds up to 270 kilometers (170 miles) per hour Mariner landed in a dust storm 3.Surface a. Less-abundant impact craters b. Numerous large volcanoes largest is Mons Olympus, 75 km above mean surface (c. f. Everest, < 9 km above msl) c. Tectonically dead d. Several canyons 1) Some larger than Earth s Grand Canyon 2) Valles Marineras the largest canyon a) Almost 5000 km long b) Formed from huge faults e. "Stream drainage" patterns 1) Found in some valleys 2) No bodies of surface water on the planet 3) Possible origins a) Past rainfall b) Surface material collapses as the subsurface ice melts 4.Moons a. Two moons Phobos 11 km, Deimos 6 km: close to surface b. Captured asteroids, probably D. Jupiter 1.Largest planet, Very massive a. 2.5 more massive than combined mass of all other planets, satellites, and asteroids b. If it had been ten times larger, it would have been a small star c. 1/800 mass of Sun 2.Movement a. Rapid rotation-- Slightly less than 10 hours b. Orbital period 4332 Earthdays 3.Banded appearance a. Multicolored Bands are aligned parallel to Jupiter's equator b. Generated by wind systems 1) Winds a) to 200 mi./h at top of atmosphere (cloud tops) b) measured to 400 mph inside Solar System Tour Page 4 of 10

5 2) Storms a) Great Red Spot i. In planet's southern hemisphere ii. Counterclockwise rotating cyclonic storm iii. Persistent over centuries other storms survive a few days b) move 7.5 degrees/day 48 days to circle planet 4.Structure gas planet a. atmosphere 90% H 2, 10% He 1) density increases into depth of atmosphere until liquid mixture 2) Surface thought to be a gigantic ocean of liquid hydrogen 3) Halfway into the interior, pressure causes liquid hydrogen to turn into liquid metallic hydrogen b. Slightly bulged equatorial region due to rapid rotation and lack of solid material c. Rocky and metallic material probably exists in a central core 5.Moons a. At least 63 moons 47 are less than 10 km diameter b. Four largest moons 1) Discovered by Galileo in 1610, Called Galilean satellites a) He wanted to name them Medicean stars, after his patron Medici b) But named by Marius in 1610 for figures in Zeus s life 2) Each has its own character very distinct from one another a) Io i. Innermost Galilean moon slightly larger than Moon ii. Volcanically active a. heat source could be from tidal energy b. internal stresses from Jupiter, and other Galilean moons iii. Sulfurous/sodium-rich surface, iron (+/- sulfur) core, molten silica mantle iv. Sulfur dioxide atmosphere v. Magnetic field of its own imbedded within Jupiter s magnetic field b) Europa i. Smallest Galilean moon ii. Icy surface a. is there liquid water beneath it? b. composition mostly rock (silicate minerals) iii. Many linear surface features what are these surface streaks? iv. weak magnetic field, tenuous atmosphere of oxygen Solar System Tour Page 5 of 10

6 c) Ganymede i. Largest Jovian satellite larger than Mercury ii. Diverse terrains a. Surface has numerous parallel grooves b. areas of craters iii. Magnetic field of its own imbedded within Jupiter s magnetic field iv. Structure inner iron +/- sulfur core, rocky mantle, ice crust d) Callisto i. Outermost Galilean moon ii. slightly smaller than Mercury, 1/3 Mercury s mass iii. Densely cratered most densely cratered body in solar system iv. composed 40% ice, 60% rock/iron; CO 2 atmosphere c. Ring system 1) dark, composed of dust (not ice, like Saturn s) 2) continually resupplied by micrometeor impacts with Metis, Adrastea, Amalthea, Thebe (four inner moons of Jupiter) 6.Interplanetary reach of Jupiter a. huge magnetic field reaches past Saturn contains charged particles b. intense radiation belt between ring and uppermost cloudtops E. Saturn 1. Smaller, but similar to Jupiter in its a. Atmosphere b. Composition c. Internal structure 2. Rings a. Most prominent feature b. Discovered by Galileo in 1610 but he didn t properly conceptualize them c. Geometry correctly inferred by Huygens in 1659 d. Complex Composed of small particles (moonlets) that orbit the planet 1) Most rings fall into one of two categories based on particle density a) Main rings contain particles from a few centimeters to several meters in diameter b) Faintest rings are composed of very fine (smoke-size) particles 2) Thought to be debris ejected from moons 3) Origin is still being debated Solar System Tour Page 6 of 10

7 3. Other features a. Dynamic atmosphere 10% polar flattening, equatorial bulge b. Large cyclonic storms similar to Jupiter's Great Red Spot c. Thirty named moons 1) Titan the largest Saturnian moon larger than Mercury a) Second largest moon in solar system (Ganymede) b) Has a substantial atmosphere N 2, 6% argon, few % methane c) surface very new i. tectonic, windblown, liquid methane, volcanic ii. There is clear evidence for "precipitation, erosion, mechanical abrasion and other fluvial activity". d) composed of water ice and rocky silicates 2) Enceladus: shiniest object in solar system new ice! 3) other moons: a) some are captured asteroids, b) Phoebe has retrograde motion F. Uranus (oorainus) discovered 1781, barely visible to naked eye 1. rock, ices, atmosphere 83% H 2, 15% He, 2% methane 2. Rotates "on its side" 3. Rings similar composition to Jupiter s rings 4. Large moons w/ varied terrains 5 are x larger than others a % water ice, remainder is rock b. Titania, Oberon, Umbriel,, Ariel, Miranda 5. Uranus and Neptune are nearly twins--bluish in appearance G. Neptune 1. Dynamic atmosphere--composed of methane a. One of the windiest places in the solar system b. Great Dark Spot disappeared, new in N hemisphere has appeared c. White cirrus-like clouds above the main cloud deck 2. Eight named satellites, five others recently discovered a. Triton largest Neptune moon nearly as big as Moon 1) Orbit is opposite other planet's travel (retrograde rotation) 2) Lowest surface temperature in the solar system (-391 F) 3) Atmosphere of mostly nitrogen with a little methane 4) Volcanic-like activity ice volcanoes 5) Water ice, layers of solid nitrogen and methane b. We know next to nothing about the other satellites of Neptune 3. Has rings like Uranus, curiously oriented magnetic field generated by?:water within planet 4. Galileo saw Neptune in 1613, but thought it was a star Solar System Tour Page 7 of 10

8 VII. MINOR MEMBERS OF THE SOLAR SYSTEM A. Dwarf planets 1. Pluto!! a dwarf planet: designated 2006 a. Discovered in 1930, misnamed as a planet b. Not visible with the unaided eye smaller than Moon, Triton, Titan, and Galilean moons c. Highly elongated orbit causes it to occasionally travel inside the orbit of Neptune, where it resided from 1979 thru February ) orbits do not cross, so they will not hit one another 2) Pluto s orbit is inclined to plane of the ecliptic about 17 o 3) axis tilts over 120 o to plane of the ecliptic d. Moon (Charon) discovered in ) over half diameter of Pluto 2) orbit of Charon is at high angle to plane of the ecliptic 3) mutually synchronous orbits same sides of each always face one another 4) Charon is mostly ices, formed independently from Pluto e. Average temperature is -210 C icy surface of N 2 (98%), methane and CO 2 f. Is it largest object of Kuiper Belt, comet, large asteroid? 2. Ceres largest object in the asteroid belt 3. Eris (formerly known as Xena) a. Discovered in 2003 b. Larger than Pluto, with a more eccentric orbit c. Nearly 100 times as far from Sun as Earth is B. Asteroids 1. Most between Mars/Jupiter; some in Jupiter s orbit, or Near Earth 2. Small bodies largest (Ceres) is about 620 miles in diameter discovered in Some have very eccentric orbits those not in asteroid belt 4. Irregular shapes 5. Composition a. 75% carbonaceous chondrite b. 17% nickel-iron silicate c. most others nickel-iron 6. Origin is uncertain total mass is 1/2 of Moon 7. Many of the recent impacts on Moon and Earth were collisions with asteroids a. Meteor Crater 1) 20,000 to 50,000 years ago 2) 10 meter diameter b. Tunguska event ) large explosion above Siberia of 60 m asteroid 2) no surface crater ever found 3) what if it was made of methane ice? Solar System Tour Page 8 of 10

9 c. Near Misses 1) in 2004 with 30 meter asteroid (43,000 km from surface) 2) in 2002 with 70 m km (1.2 x Moon s diatance) 3) Asclepius March 29, 1989, 1000 m, 400,000 km (passed where Earth was 6 hours earlier C. Comets 1. Often compared to large, "dirty snowballs" 2. Composition a. Frozen gases ices of water, ammonia, methane, CO 2, CO b. Rocky and metallic materials cemented by the ices 3. Frozen gases vaporize when near the Sun a. Produces a glowing head called the coma ~ Jupiter diameter, with tiny nucleus inside b. Some may develop a tail that points away from Sun due to 1) Radiation pressure on dust 2) Solar wind pressure on ionized gases 3) this material is lost from comet forever, so reduced in size each time c. gases recondense upon leaving vicinity of Sun, so no longer spectacular 4. Origin Not well known form at great distance from Sun a. Short-period comets < 200 years 1) Probably from Kuiper belt beyond Neptune a) fairly circular orbits of these objects close to plane of other planets b) occasional collisions, perhaps perturbed orbits due to gravity of gas giants, throw Kuiper belt objects into eccentric orbits that pass close to Sun 2) Most famous short-period comet is Halley's comet a) 76 year orbital period i. tail 1 million miles long, ii. could be seen in daytime 1910 b) Potato-shaped nucleus (16 km by 8 km) fizzing, cratered per Giotto probe in ) Hale-Bopp in 1997 spectacular! a) had twin tail that spanned 1/5 of night sky 15 million miles long b) 40 km diameter nucleus b. Long-period comets 1) period perhaps > 100,000 years 2) may originate in Oort Cloud a) hypothetical region containing a combined mass of objects greater than the mass of Jupiter beyond Kuiper Belt b) in spherical shell around solar system Solar System Tour Page 9 of 10

10 D. Meteoroids 1. Called meteors when they enter Earth's atmosphere shooting star 2. A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet's path 3. Meteoroids are referred to as meteorites when they are found on Earth a. Types of meteorites classified by their composition 1) Irons most commonly found a) Mostly iron, 5-20% nickel b) May give an idea as to the composition of Earth's core c) Give an idea as to the age of the solar system 4.5 billion years 2) Stony most common type a) Silicate minerals with b) Inclusions of other minerals 3) Stony-irons mixtures 4) Carbonaceous chondrites Rare a) Simple amino acids b) Other organic material b. Meteor crater 1) 1.2 km across, 170 m deep 2) Significant amount of iron debris surrounding the crater c. Manicouagan, Quebec structure is 200 million years old d. Shoemaker-Levy 9 collision with Jupiter 4. origins of meteoroids a. interplanetary debris not swept up on accretion of planetary bodies b. displaced objects from asteroid belt c. remains of disintegrated comets Solar System Tour Page 10 of 10