a1_13_venus

a1_13_venus - Venus: Earths (Evil) Twin Some basic numbers...

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Venus: Earth ʼ s (Evil) Twin
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Some basic numbers Semi-major axis: 0.723 AU (67.1 million miles) Orbital Eccentricity: 0.0068 Orbital Inclination: 3.4 degrees Orbital Period: 224.68 days Sidereal rotation period: 243.01 days Diameter 12,104 km (~ 7500 miles) Density: 5.24 g/cc (4.2 uncompressed) Mass (Earth = 1): 0.815 Obliquity: 177.4 degrees Number of satellite: 0 Surface temperature: 745 K ( ~ 880 F) Albedo (cloud tops): 0.76 Atmospheric Pressure at surface (Earth ~ 1 bar): 90 bars
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Venus…as seen through a telescope.
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Because Venus is closer to the Sun, it goes through phases like the Moon. And it changes its apparent size (angular diameter).
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Venus ʼ thick atmosphere prevents imaging its surface directly…so must use radar mapping Visible light UV light
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Launch Date: 04-May-1989 Arrival Date: 10-Aug-1990 End of Mission: 12-Oct-1994 Magellan
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Magellan was the frst planetary spacecraFt to be launched From a space shuttle. It orbited Venus in a near polar, elliptical orbit, with a minimum altitude (periapsis) oF 243 kilometers (150 miles). It made detailed maps oF 98% oF the planet's surFace using synthetic aperture radar. Magellan revealed no evidence on Venus oF plate tectonics, such as operates with such proFound eFFect on Earth. Volcanoes have leFt their marks on 85% oF Venus, with lava plains, lava domes, large shield volcanoes, and extremely long lava channels. The rest oF the surFace is covered with ranges oF deFormed mountains. Magellan also made detailed gravity maps oF Venus, determining that the gravity feld is highly correlated with surFace topography. NASA
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Although about the same size as Earth, Venus has a very different surface topography.
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Venus has only two major Continents: Ishtar Terra near the North Pole and Aphrodite Terra along the equator
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NASA
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Polar regions NASA
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NASA Impact Craters Because Venus ʼ atmosphere is so dense, small meteorites break up as they fall, creating clusters of overlapping craters. The dark terrain around these craters is covered by a layer of Fne material pulverized by the meteorite impact. Width of image area: 95 km (59 mi.)
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A 3D view of the 37 km wide impact crater Howe
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Impact craters, cont ʼ d Most of the ~1000 craters look very young, less than 700 million yrs old. This suggests little erosion. Craters appear randomly scattered over the surface. So apparently we are seeing a globally “young” Venus. This raises the question of what has made the surface so uniformly “young” ?
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Catastrophe or Uniformitarianism The finding of sparse, pristine, and randomly distributed craters on Venus led to a debate about why this is. – One explanation said volcanic eruptions destroy craters
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This note was uploaded on 05/05/2010 for the course ASTR 001 taught by Professor Robertfesen during the Spring '10 term at Dartmouth.

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a1_13_venus - Venus: Earths (Evil) Twin Some basic numbers...

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