Solar System October 5, 2006 I. Overview of the solar system—Solar system includes A. Sun 1. 99.85% 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 II. 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: +700o 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 (NH3) 2. Methane (CH4) 3. Carbon dioxide (CO2) 4. Water (H2O) D. Nebular cloud hypothesis of Solar System formation explains why inner planets and outer planets are different: temperatures and melting temperatures III. Planetary information A. Mercury 1.Innermost planet 2.smallest planet 4880 km diameter 3.orbit a. inclined 7o 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 Solar System Tour 2006.10.05 Page 1 of 92) 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 (-280˚F) 2) Hot days (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 2o (1780 retrograde) 2.Similar to Earth a. Size 12000 km (c.f. 12756 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% N2, trace H2O 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 that are mantled 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 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% N2, 1.6% Ar, trace H2O c. Cold polar temperatures (-193˚F) d. Polar caps of water ice, covered by a thin layer of frozen carbon dioxide Solar System Tour 2006.10.05 Page 2 of 9e. 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, Deimos b. Captured asteroids D. Jupiter 1.Largest planet, Very massive a. 2.5 more massive than combined mass of the 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 2) Storms a) move 7.5 degrees/day—48 days to circle planet b) Great Red Spot i. In planet's southern hemisphere ii. Counterclockwise rotating cyclonic storm iii. Persistent over centuries—other storms survive a few days 4.Structure—gas planet a. atmosphere 90% H2, 10% He Solar System Tour 2006.10.05 Page 3 of 91) 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 28 moons 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) 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; CO2 atmosphere 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 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) 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,
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