VENUS

Vital Statistics:

Orbital Semimajor axis = 0.7 AU

Orbital Period = 224.7 days

Rotation Period = 243 days (retrograde!)

Axial tilt = 3^o

Diameter = 12,104 km

Density = 5.3 g/cm³

Surface Temperature = 750K (477^oC or about 1000^oF)

Albedo = 0.65

Satellites = none

Explored by: (U.S.) Mariner 2 (1962), 5 (1967), 10 (1974)

Pioneer 12, 13 (1978) (also known as Pioneer Venus 1 and 2)

Magellan (1989)

(USSR) Zond-1 (1964), Venera 2(1965), Venera 3 (1965)

Venera-4 (1867), Venera 5 (1969), Venera 6 (1969),

Venera 7 (1970), Venera 8 (1972), Venera 9 (1975),

Venera 10 (1975), Venera 11 (1978), Venera 12 (1978),

Venera 13 (1981; color pictures), Venera 14 (1981),

Venera 15 (1983) and Venera 16 (1983) orbiters,

Vega 1 (1984), Vega 2 (1984) [Vega 1 & 2 also studied Halley’s comet]

Interior:

Similar to Earth: Fe-Ni core, peridotite mantle, crust

Venus has NO magnetic field

Atmosphere:

CO₂-rich (surface pressure 90X Earth; equivalent to ~ 1 km under ocean);

Just over 3% of atmosphere is N₂

Virtually no water in atmosphere or surface

Run-away Greenhouse effect!

SO₂-rich clouds with sulfuric acid rain; winds at 350 km/hr at cloud tops, dropping to 3 km/hr at surface

Atmosphere moves westward faster than Venus rotates; air movement is mostly N-S in two “Hadley cells”

Surface Features:

Has "continents" (Ishtar Terra, Aphrodite, Beta Regio)

and ocean basins floored by BASALT

Extensive rift faults, especially at equator

TESSERAE ("tile") = chaotic fracture areas (fig.10.32 in text)

Evidence for some fold mountains on continents at upper and lower latitudes

Impact Craters (most impactors explode before reaching surface) Cratering rates indicate a surface age of no more than 800 million years

"Coronae"; rounded domes, possibly upwelling viscous magma bodies, with

"subduction" at margins

Pancake structures

Arachnoids

VOLCANOES (shield type); extensive especially associated with rifting

Venus has had hotspot activity, but apparently no real plate tectonics like that on Earth (crust too hot to sink AND volatiles required for melting to produce asthenosphere lost during extensive volcanism about 800 million years ago)