GEOL3045: Planetary Geology
GEOL3045: Planetary Geology
Lysa ChizmadiaVenus
From Mariner to Venera to Venus Express
Lysa ChizmadiaVenus
From Mariner to Venera to Venus Express
IntroductionIntroduction 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
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
Image from: http://www.nineplanets.org/venus.html
Shows phases Supported
Copernicus’ heliocentric theory
Mean surfaces temperature = 462C ~isothermal Hotter than Mercury
Shows phases Supported
Copernicus’ heliocentric theory
Mean surfaces temperature = 462C ~isothermal Hotter than Mercury
Earth’s Twin PlanetEarth’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
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
Rare impact crater on Venus
Images from: http://en.wikipedia.org/wiki/Venus
Relative sizes of the terrestrial planets
Venusian GeographyVenusian 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
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 Image from:
http://www.nineplanets.org/venus.html
Magellan radar map (false color)
Image from: http://en.wikipedia.org/wiki/Venus
Map of Venus, higher elevations in reds & yellows
Venusian AtmosphereVenusian 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
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 atmosphereImages from:
http://en.wikipedia.org/wiki/Venus
Venus in visible light
Venus in UV light
Venusian VolcanismVenusian 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?
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
Pancake volcanoes in Alpha Regio regionImages from:
http://www.geology.sdsu.edu/how_volcanoes_work/venus.html
Radial lava flows Sapas Mons
Coronae & ArachnoidsCoronae & 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
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
Image from: http://www.nineplanets.org/venus.html
Pandora Coronae
Images from: http://www.geology.sdsu.edu/how_volcanoes_work/venus.html
Ba’het Coronae
Arachnoids
Prominent U.S. SatellitesProminent U.S. Satellites Mariner 2:
First satellite to visit Venus Flyby in December 1962 Discovered Venus is very hot
(~800C) 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
Mariner 2: First satellite to visit Venus Flyby in December 1962 Discovered Venus is very hot
(~800C) 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
Venera 7, 9 & 10Venera 7, 9 & 10 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 485C Windspeed 3.5 m/s
Also Venera 11-16 Detected possible seismic
activity Observed strong lightning Discovered pancake volcanoes,
coronae & arachnoids
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 485C Windspeed 3.5 m/s
Also Venera 11-16 Detected possible seismic
activity Observed strong lightning Discovered pancake volcanoes,
coronae & arachnoids
Image from: http://www.nineplanets.org/venus.html
Venusian surface from Venera 9
Image from: http://en.wikipedia.org/wiki/Venera_10
Venusian surface from Venera 9 & 10
Image from: http://www.solarviews.com/eng/venus.htm
Venusian surface from Venera 13
SummarySummary 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)
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)