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GEOL3045: Planetary Geology

GEOL3045: Planetary Geology. Lysa Chizmadia Venus From Mariner to Venera to Venus Express. Second planet from the Sun Distance = 1.1 x 10 8 km 0.72 AU Diameter = 1.2 x 10 4 km Mass = 4.9 x 10 23 kg Very circular orbit Eccentricity < 1% Aphelion: 1.09 x 10 8 km

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GEOL3045: Planetary Geology

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  1. GEOL3045: Planetary Geology Lysa Chizmadia Venus From Mariner to Venera to Venus Express

  2. Second planet from the Sun Distance = 1.1 x 108 km 0.72 AU Diameter = 1.2 x 104 km Mass = 4.9 x 1023 kg Very circular orbit Eccentricity < 1% Aphelion: 1.09 x 108 km Perihelion: 1.07 x 108 km Retrograde rotation From east to west Venusian day = 243 days Venusian year = 225 days Shows phases Supported Copernicus’ heliocentric theory Mean surfaces temperature = 462C ~isothermal Hotter than Mercury Introduction Image from: http://www.nineplanets.org/venus.html

  3. Earth’s Twin Planet • Similar sizes: • 1.2 x 104 km (95% of ) •  = 1.3 x 104 km • Similar masses: • 4.9 x 1023 kg (80% of ) •  = 6.0 X 1024 kg • Similar densities • 5.25 g/cm3 vs. 5.52 g/cm3 vs. • Similar bulk compositions • Young surfaces • Recent geologic activity • Including volcanism & weathering Relative sizes of the terrestrial planets Rare impact crater on Venus Images from: http://en.wikipedia.org/wiki/Venus

  4. Venusian Geography • Highlands (~ continents) • Ishtar Terra ~ size of Australia • Northern hemisphere • Interior high plateau: Lakshmi Planum • Surrounding by highest mountains • Maxwell Montes • Highest mts have high albedo substance • Speculation: Te & PbS • Aphrodite Terra ~ size of S. America • Equator • Broad depressions (~ ocean basins) • Atalanta Planitia • Guinevere Planitia • Lavinia Planitia Map of Venus, higher elevations in reds & yellows Image from: http://en.wikipedia.org/wiki/Venus Magellan radar map (false color) Image from: http://www.nineplanets.org/venus.html

  5. Venusian Atmosphere • Densest of all terrestrial planets • 96.5% CO2 & 3.4% N2 • 90-92 times thicker than  • Greenhouse effect • Responsible for high Ts • Receives 25% of sunlight as Mercury • Clouds of CO2 & H2SO4 • Atm contains 0.015% SO2 • Has intermittent lightning • Indicates weathering • Venus Express 2005-2009 • Studying atmosphere Venus in visible light Venus in UV light Images from: http://en.wikipedia.org/wiki/Venus

  6. Venusian Volcanism • Magellan’s radar showed much of Venus is covered in lava flows • Several shield volcanoes • E.g. Sif Mons & Sapas Mons • >152 volcanic domes • Flat-top domes called pancake domes • Consistent w/ viscous lavas • High silica lavas? Sif Mons Radial lava flows Sapas Mons Pancake volcanoes in Alpha Regio region Images from: http://www.geology.sdsu.edu/how_volcanoes_work/venus.html

  7. Coronae & Arachnoids • Coronae • Circular raised structures surrounded by ridges & grooves & radial lines • Seem to be collapsed domes over large magma chambers • E.g. Crater Lake • Arachnoids • Ovoid features w/ concentric rings & complex fracture networks • Similar but smaller than coronae • Possibly precursor to coronae Pandora Coronae Image from: http://www.nineplanets.org/venus.html Ba’het Coronae Arachnoids Images from: http://www.geology.sdsu.edu/how_volcanoes_work/venus.html

  8. Prominent U.S. Satellites • Mariner 2: • First satellite to visit Venus • Flyby in December 1962 • Discovered Venus is very hot (~800C) w/ dense CO2-rich atmosphere • Pioneer Venus in 1978 • Orbiter & 4 atmospheric probes • Made 1st high quality map of Venus • Magellan in 1989 • Mapped 98% of surface • Gravity field map for 95% of surface

  9. Venera 7, 9 & 10 Venusian surface from Venera 9 Image from: http://www.nineplanets.org/venus.html • Venera 7 in 1970 • 1st probe to return surface data from another planet • Venera 9 & 10 in 1975 • 1st spaceship to land on another planet • Clouds 30-40 km thick • Pressure 90 atm • Temperature 485C • Windspeed 3.5 m/s • Also Venera 11-16 • Detected possible seismic activity • Observed strong lightning • Discovered pancake volcanoes, coronae & arachnoids Venusian surface from Venera 9 & 10 Image from: http://en.wikipedia.org/wiki/Venera_10 Venusian surface from Venera 13 Image from: http://www.solarviews.com/eng/venus.htm

  10. Summary • Earth’s twin in size & bulk composition • Also, young surfaces • Geologic activity & weathering • Densest atmosphere for terrestrial planets • ~90 times higher than Earth • Greenhouse effect keeps T high & constant • Lightning & “snow” indicate weather • Prominent features include • Volcanoes (shield & pancake) • Coronae (magma rising) • Arachnoids (collapsed volcanoes)

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