Its day is longer than its year!
The sun rises in the west and sets in the east 58.4 days later.
Soil samples from surface show density of 3 g/cm3 (similar to basalt on Earth)
Discovered atmosphere was hot and CO2 rich, with very high atmospheric pressure (high enough to crush a spacecraft)
1970 - Venera 7 (USSR) - modified to withstand extreme temperatures and pressures. Landed. Transmitted data for 23 minutes.
Temperature was measured at 890 degrees F.
Photos were taken on subsequent missions.
Discovered sulfuric acid clouds
Radar mapping by:
Very complex atmospheric chemistry
Very corrosive atmosphere
Haze and main cloud deck = 50 - 70 km high, with clouds 20 km thick.
Clouds are made of sulfuric acid droplets, sulfur particles, and other sulfur compounds.
Sulfuric acid rain evaporates before reaching the planet's surface.
Almost no visible light gets through the 20-km-thick clouds
Clouds are pale yellow and reflect 75 - 85% of the incoming light from the sun.
Only 2.5% of the incoming solar radiation reaches the surface of Venus
The rest is absorbed by the atmosphere causing heating; the clouds re-radiate heat.
This is called the Greenhouse Effect
Probably no water condensation ever to form oceans.
Slow atmospheric circulation causes only a weak Coriolis Effect; simple equator to pole circulation
Photos show rocky desert with regolith ("soil")
More than 100 impact craters were found by Venera 15 and 16, leading to an age estimate for the plains (based on crater density) of 300 million years to 1 billion years.
This is younger than the lunar maria, but older than Earth's oceanic crust (which is a maximum of 150-200 million years).
Corona structures are present.
They are circular features 200-600 (or even 800) km in diameter
Surrounded by basalt flows.
May lie above old volcanic hot spots (mantle plumes).
Later cooled and collapsed to form wrinkled calderas with radial fractures.
Probably located on upwelling and extensional (divergent) rift areas.
Two "continents" and several smaller elevated areas.
The range of elevations is only 14 km (compared to Earth's 20 km range). No deep trenches.
The highest elevations are over 3 km; most of the uplands are 1 - 3 km.
Over 70% of the surface is low rolling plains less than 1 km high.
Radar shows "bright" areas, suggesting that the plains are lava flows (basalt)
Aphrodite Terra is plateau-like with linear troughs. May be a region of crustal spreading (rifting) with transform faults.
Ishtar Terra is the highest area on the planet, with mountains up to about 11 km high.
Tallest mountain is Maxwell Montes (the only feature on the planet named for a man, the discoverer of radar).
Its height is comparable to Mt. Everest on Earth, which is 12 km above Earth's mean radius.
Linear mountain belts 1000-1200 km long and several km wide.
May be evidence of crustal compression (folded mountains), or lines of volcanism.
Southern edge of Ishtar Terra has a steep 3 km drop, and has been interpreted as a subduction zone.
Upland plain on Ishtar Terra is called Lakshmi Planum.
There are two large circular features on Lakshi Planum, which may be volcanic calderas, possibly the source of flood basalts.
Beta Regio is associated with a major rift system, and has what appears to be 2 shield volcanoes, about 5 km high.
Venera 9 and 10 landed in this area.
May be characterized by hot spots
Basaltic volcanism may be responsible for smooth plains.
Possible reason? Slow rotation rate.
Result? Solar wind can hit the atmosphere and cause the atmosphere to ionize.
Ionosphere trails out "downwind" in a plasma tail.
Causes turbulence in atmosphere.
Solar wind particles are slowed down by the atmosphere (called bow shock) and are forced around the planet.
Solar wind does not reach the planet's surface.
This page created on February 25, 1996
by Pamela J. W. Gore
DeKalb College, Clarkston, GA
pgore@gpc.edu