Venus

Structure

Venus's Structure
Feature % of radius
Inner Core 17%
Outer Core 30%
Mantle 52.5%
Crust .5%
Atmosphere 3%

The Inner Core
Venus's inner core is composed of iron-nickel. Although it is hot enough to melt, the tremendous pressure on top of it keeps it solid.

The Outer Core
Venus's outer core is also composed of iron-nickel, but unlike the inner core, it is not put under enough pressure to make it a solid.

The Mantle
Venus's mantle is a thick, melted mixture of silicates and relatively small amounts of metallic oxides. Though Venus's mantle is less powerful than Earth's, it still convects, causing continental drift.

The Crust
Venus's crust is made of rock silicates and metals. Subsurface rock is more plastic than on Earth, absorbing the energy of continental drift. However, there are still volcanoes caused by collisions of plates. No active ones have been discovered yet, and there are fewer than on Earth. Some are higher than Mount Everest. Venus's crust has faults, formed by the pulling apart of a continental plate. It also sports features called ovoids, so called because they are very round. Ovoids can be hundreds of miles in diameter. They may be caused by upwellings of lava from the interior.

The Atmosphere
Although Venus's atmosphere is very thin compared to features like its mantle and cores, its atmosphere is where all the action happens. Venus's atmosphere is composed of mostly carbon dioxide, with nitrogen, argon, sulfuric acid, and water vapor.

History

Early in its history, Venus was much like Earth. It had an atmosphere a lot like ours and might have even had rivers and oceans. But because Venus was closer to the sun than Earth was, different chemical processes began to occur. The sun slowly boiled away Venus's surface water. With a heavy water vapor atmosphere, the greenhouse effect took hold. The temperature rose enough that large amounts of carbon dioxide, trapped in the surface rocks, were released into the atmosphere. With carbon dioxide in the air, the greenhouse effect became much more efficient and the temperature shot up. It became so hot that some of the water vapor in Venus's atmosphere broke up chemically into hydrogen and oxygen. Simple sulfur compounds freed from the Venusian crust joined with with these byproducts chemically to form sulfuric acid. The leftover oxygen was trapped in the rocks of Venus's crust, and the leftover hydrogen eventually escaped into space.
Venus is the third brightest object in the sky, behind the Sun and the Moon. Sometimes it even casts shadows at night. So, of course, it was known even to ancient astronomers.
Until American Mariner and Soviet Venera spacecraft studied the planet Venus, it was thought to be a twin of Earth. Venus's thick, opaque clouds gave people the opportunity to believe whatever they wanted to believe about the planet. It seemed reasonable then that because Venus's size, mass, and density were so close to Earth's, it would resemble Earth closely in other aspects as well. People imagined Venus as a lush Garden of Eden overflowing with plant and animal life. They were very surprised when the readings came back from the Mariner spacecraft that Venus had such a harsh environment.

The Greenhouse Effect

 Almost all of Venus's atmosphere is carbon dioxide. This carbon dioxide atmosphere covers Venus like the glass covering a greenhouse, hence the term "greenhouse effect." High-energy radiation from the sun, ultraviolet light, for example, passes right through Venus's carbon dioxide atmosphere. This is like when visible light passes through the roof of a greenhouse. The radiation proceeds to the ground, where it is absorbed and re-radiated as infrared energy (heat.) The same happens in a greenhouse; the plants absorb the light and re-radiate it. The new long-wave, low-energy light cannot get through the carbon dioxide (or the glass.) It is either absorbed, convected, and re-radiated, or reflected immediately. The heat accumulates, and the environment becomes very hot. Of course, a lot of energy escapes from a greenhouse; the temperature inside a greenhouse is very tolerable. But on Venus, the greenhouse effect is very efficient, raising Venus's temperature to 900° F, or 480° C.

Customary Metric Comparison to Earth
Equatorial Diameter 7,521 mi 12,104 km Earth is about 5% wider than Venus
Polar Diameter 7,521 mi 12,104 km Earth is about 5% taller than Venus
Mean Density 5.24• water density 1 tsp of Venus weighs 95% as much as 1 tsp of Earth
Mass 1.073• 1025 lbs 4.867• 1024 kg Venus weighs about 80% as much as Earth
Grav. Acceleration 28.2 ft/sec² 8.6 m/sec² G-force on Venus is .9 G's
Escape Velocity 6.6 mi/sec 10.62 km/sec Have to go 1900 ft (600 m) / sec faster to escape Earth
Number of Moons None Earth has 1 more moon than Venus
Distance to Sun: Average 67,200,000 mi 108,100,000 km Earth is 40% further from the sun
Minimum 66,700,000 mi 107,300,000 km
Maximum 67,700,000 mi 109,000,000 km
Orbital Velocity: Average 78,360 mph 126,110 kph Venus goes 18% faster in its orbit
Minimum 77,810 mph 125,220 kph
Maximum 78,910 mph 126,990 kph
Orbital Period 224.7 Earth days A Venus year is 60% of an Earth year
Orbital Eccentricity .007 Venus's orbit is slightly closer to a circle
Orbital Inclination 3.4° Venus's orbit is tilted 3.4° from Earth's
Axal Inclination 3° Earth's tropical and arctic zones are 8 times as wide
Rotational Period 243.02 Earth days Venus takes 243.02 times as long to rotate on its axis
Albedo 65% If both recieve equal light Venus will be almost twice as bright
Surface Temperature 835-900° F 445-480° C Venus's record low is 700° F (420° C) hotter than Earth's record hottest
The Inner Planets
Next Planet: Earth