Astronomy test #2 - Venus Craters 2-280 km no small craters...

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Venus - Craters - 2-280 km, no small craters, meteoroids burn up in atmosphere, crater density 15% of lunar Maria (low). Basins- none observed, surface is new. Tectonic -cracks and ridges present, continents (Ishtar & Aphrodite), mountains, no plate tectonics. Volcanism - 80% of the surface lava plains, happened 500 mya, large-scale volcanism in the past, lower than it was 500 mya, shield volcanoes, farra (pancake dome), lava rivers, arachnoids, coronas. Surface : Basalt. Atmosphere - 96.5% co2, 3.5% N2, air rises at equators sinks at poles. Pressure 100x earths, large green house gas effect, very warm no oceans to absorb Co2 Temp: 735 K (860 f). Axis tilt 177.36, no seasons, retrograde motion. Clouds - composed mostly of sulfuric acid (H2So4) and So2, highly reflective, reflects 60% of sunlight, H2So4 rains never reaches surface, so hot evaporates quickly. Interior - similar to earths, partially liquid core, density 5.3 g/cm3. Magnetic Fields - extremely weak, slow rotation 243 days. orbital period 224 days solar day 117 days-retrograde motion. Sidereal day> solar day. Mars - Craters - similar to airless planets (mercury moon) no rays, fluidized ejecta, few craters in uplands (erosion erased them), 10(uplands) .1(near volcano of lunar maria). Basins- fewer then moon, erosion geologic activity. Tectonics - fracturing on surface, great canyon (half of the US), landslides increase canyon size, no large plates. Volcanism -many shield volcanoes, Olympus Mons largest volcano of any planet, no large composite volcanoes or lava rivers, all volcanoes are dormant. Erosion - wind/water, wind fills craters w/ sand, water -runoff channels - found in uplands, similar to earth drainage system, 4 bya, 10-100 m wide 10-100 km long, few tributaries, small channels erased by erosion, outflow channels - confined to equatorial plain, 3 bya, 10km wide, 10-100km long, drop several km in elevation, multiple channels diverge & interconnect, tear shaped inlands at mouth of outflow, catastrophic flood, chaotic terrain may have continued after flood. Gullies - found at high latitudes on shaded walls and channels, debris apron on wind blown deposits, recent occurring, origins - melting of permafrost due to magma chamber heat. Surface - fine grained dust, reddish from iron-oxide (rust). Atmosphere - 95.4% Co2, 2.7% N2, 1.6% Ar, .13% 02, .07% Co, .03% H2o. Pressure- 1/150 of earths Temp: 180K (-125f) to 265k (23f). Axis tilt- 25, similar to earths. Weather - low latitudes, Hadley circulation, high altitudes baroclinic pressure wave, series of high/low pressure areas, has cyclones/dust storms. Interior - density 3.9 g/cm3, Iron sulfide (FeS) core, partially liquid and solid, small magnetic field, mostly crustal in origin, was stronger in past (4bya). Polar Ice - seasonal/permanent ice caps. Seasonal - north goes 65* N, south goes 55* S, retreat 20 km/day during spring, composed of Co2 (dry ice). Permanent- South- 350 km in diameter, remains at 150k during summer, composed of h2o and Co2, North- larger, 1000km in diameter, temp rises above 200k in summer, composed of h2o. Polar Terrain
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This note was uploaded on 04/04/2012 for the course ASTRO 138 taught by Professor Nicholascerrutti during the Spring '11 term at Washington State University .

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