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Quark’s Holiday Tour Part II: the Inner Planets of Sol Mars Venus Mercury Terra Jupiter N. Lindsley-Griffin, 1998 Geology of Terrestrial Planets Quark’s Holiday Tour Composition - All have: metallic core siliceous mantle basaltic crust Relatively dense: 4 - 5.5 g/cm3 Different history from Jovians All shaped by: 1. Impact cratering 2. Volcanism 3. Tectonism 4. Erosion and deposition Terra (“Earth”) Luna (“Moon”) Venus Mars Mercury Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 Evolution of Terrestrial Planets Quark’s Holiday Tour A planet’s evolution is controlled by how long internal heat lasts Luna (Earth’s Moon) is small, became quiet 3 b.y. ago Terra (“Earth”) is large, stilll hot, remains dynamic today N. Lindsley-Griffin, 1999 Atmospheres - Venus, Earth, Mars Quark’s Holiday Tour Venus - runaway greenhouse effect No plate tectonics Too much Solar energy Earth - plate tectonics recycles oxygen by subducting and remelting oceanic lithosphere and sediments Carbon dioxide trapped biogenically Size and mass just right to maintain internal heat that drives tectonic cycle Mars - water, oxygen locked up in rocks No plate tectonics Too small to hold dense atmosphere Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 Venus - carbon dioxide Earth - nitrogen/oxygen Mars - carbon dioxide LUNA Crater Density and Age of Surface Many craters on older, original lunar crust (anorthosite brecciated by repeated impacts) Crater Density (arbitrary units) Quark’s Holiday Tour A Fewer craters on younger crust of basalt in the lunar mare (dark colored basins) Crater density provides relative dating for lunar surfaces B N. Lindsley-Griffin, 1999 C b.y. ago D MARS: Tectonics Quark’s Holiday Tour Huge rift valleys (grabens) cut the northern hemisphere Valles Marineris, largest canyon in the solar system, is 4500 km long, 2-7 km deep, formed by crustal rifting Tharsis Bulge, shield volcanoes N. Lindsley-Griffin, 1998 Valles Marineris, a graben MARS: Olympus Mons Quark’s Holiday Tour Largest volcano in the solar system Shield Volcano Summit Caldera Larger than the entire Hawaiian islands No linear track (therefore no plate tectonics) N. Lindsley-Griffin, 1998 MARS: Atmosphere Quark’s Holiday Tour Atmosphere is thin, rich in CO2 Iron in rocks has weathered to red oxides Winds produce ventifacts and dune fields, deposit wind-blown sediments N. Lindsley-Griffin, 1998 MARS: Climate and Ice Caps Quark’s Holiday Tour Strongly elliptical orbit causes huge variation in seasons Average temp. -55°C (-67°F), but ranges from winter low of -133°C (-207°F) to summer high of 27°C (80°F) Ice caps wax and wane with the seasons, causing 25% change in global atmospheric pressure Ice caps at both poles are carbon dioxide (“dry ice”) with dust and minor water ice. N. Lindsley-Griffin, 1998 MARS: Water Cycle Quark’s Holiday Tour Liquid water cannot exist on surface today No water cycle active today Evidence of water erosion and deposition in the past Major climate change N. Lindsley-Griffin, 1998 MARS: Water Cycle Quark’s Holiday Tour Large floods Small river systems Large lakes or even oceans Runoff caused by impact? Nirgal Vallis, a runoff channel Fault-bounded canyon N. Lindsley-Griffin, 1998 VENUS: Atmosphere Quark’s Holiday Tour Pressure: 90 atm. Dense clouds of CO2 and sulfuric acid conceal surface Runaway greenhouse effect traps solar heat at surface Surface temperature 500o C (melts lead) N. Lindsley-Griffin, 1998 VENUS: Radar View of Surface Quark’s Holiday Tour No rivers, oceans Surface 500°C greenschist metamorphism No plate tectonics only hot spot volcanism N. Lindsley-Griffin, 1998 VENUS: Mountains and Faults Quark’s Holiday Tour Linear features are tension cracks (normal faults) Structures are horsts and grabens like the Basin and Range Province Form over rising or sinking mantle plumes N. Lindsley-Griffin, 1998 Normal Faults Grabens VENUS: Volcanoes, Lava Flows Quark’s Holiday Tour Radar images show large shield volcanoes Entirely basaltic crust Sif Mons, a shield volcano - no granite Fresh, uncratered lava flows Dark lava flows are smooth, less reflective, pahoehoe lava Bright radar images are rough aa lava N. Lindsley-Griffin, 1998 Maat Mons Volcano, Venus Younger Impact Crater Older Lava Flow Younger Lava Flow Older Lava Flow The entire surface of Venus is covered by 500 m.y. basalt Suggests a catastrophic resurfacing event Sparse impact crater density -little modification since then N. Lindsley-Griffin, 1998 MERCURY Quark’s Holiday Tour Closest planet to Sol Smaller than all other planets except Pluto No atmosphere Rotates only 3 times in 2 of its years N. Lindsley-Griffin, 1998 MERCURY: Geology Quark’s Holiday Tour Surface very old, heavily cratered, similar to Luna Huge lava plains like Lunar maria N. Lindsley-Griffin, 1998 Sol: Close Approach Quark’s Holiday Tour As we zoom around Sol on our way to Terra…. Solar flare or prominence Dark sunspots are relatively “cool” regions N. Lindsley-Griffin, 1998 TERRA - LUNA Quark’s Holiday Tour The moon Luna is 1/4 the diameter of Terra Some scientists consider these to be paired planets like Pluto - Charon Luna’s relatively great mass affects ocean tides on Terra N. Lindsley-Griffin, 1998 LUNAR GEOLOGY Quark’s Holiday Tour Terrae, or lunar highlands (red color), the older crust under basalt lava flows Maria, or lunar lava flows, (blue and orange color) are the younger lowlands Tycho crater: Rays of young ejecta cut across older features Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 LUNAR METEORITE IMPACT Quark’s Holiday Tour Large crater excavated by impact. Meteorite disintegrates, debris scatters all around. Secondary craters formed by impact of larger ejecta fragments. Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 LUNAR METEORITE IMPACT Quark’s Holiday Tour ORIGIN OF LUNAR MARIA Impact forms normal faults and ring fractures around crater Basaltic magma forms by pressure-release melting, ascends through fractures to fill crater. Result: younger, less cratered basaltic maria. Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 LUNA Crater Density and Age of Surface Many craters on older, original lunar crust (anorthosite brecciated by repeated impacts) Crater Density (arbitrary units) Quark’s Holiday Tour A Fewer craters on younger crust of basalt in the lunar mare (dark colored basins) Crater density provides relative dating for lunar surfaces B N. Lindsley-Griffin, 1999 C b.y. ago D TERRA: Unique! Quark’s Holiday Tour Oxygen-rich atmosphere Over 70% surface is water Plate tectonics recycles oxygen and water Only known life in Solar System (but is it intelligent?) N. Lindsley-Griffin, 1998 TERRA: Intelligence? Quark’s Holiday Tour Hope for the future: The U-manz (Terrans) are building a space station. - a primitive step towards exploring the universe - people and nations who were enemies not long ago are working together. Let’s hope they finish growing up before they invade us! N. Lindsley-Griffin, 2000 THAT CONCLUDES OUR TOUR Enjoy your Holiday! Quiz 9 - 100 pts. extra credit over the locations on this tour of the solar system - will be active until 5:00 PM Wednesday Dec. 13 N. Lindsley-Griffin, 1998