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Venus, Second Planet from the Sun, Brightest Planet in Solar System

Venus’ atmosphere traps heat from the Sun as an extreme version of the greenhouse effect that warms Earth. The temperature on Venus are hot enough to melt lead.
Credit: NASA

Venus, the second planet from the sun, is named for the Roman goddess of love and beauty. The planet — the only planet named after a female — may have been named for the most beautiful deity of her pantheon because it shone the brightest of the five planets known to ancient astronomers.

In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise. In Latin, they were respectively known as Vesper and Lucifer. In Christian times, Lucifer, or "light-bringer," became known as the name of Satan before his fall.

Physical characteristics

Venus and Earth are often called twins because they are similar in size, mass, density, composition and gravity. However, the similarities end there. [Photos: Venus, the Mysterious Planet Next Door]

Venus is the hottest world in the solar system. Although Venus is not the planet closest to the sun, its dense atmosphere traps heat in a runaway version of the greenhouse effect that warms Earth. As a result, temperatures on Venus reach 870 degrees F (465 degrees C), more than hot enough to melt lead. Probes that scientists have landed there have survived only a few hours before getting destroyed.

Venus has a hellish atmosphere as well, consisting mainly of carbon dioxide with clouds of sulfuric acid, and scientists have only detected trace amounts of water in the atmosphere. The atmosphere is heavier than that of any other planet, leading to a surface pressure 90 times that of Earth.

Venus' southern hemisphere, as seen in the ultraviolet.
Venus' southern hemisphere, as seen in the ultraviolet.
Credit: ESA

The surface of Venus is extremely dry. There is no liquid water on its surface because the scorching heat would cause any to boil away. Roughly two-thirds percent of the Venusian surface is covered by flat, smooth plains that are marred by thousands of volcanoes, ranging from about 0.5 to 150 miles (0.8 to 240 kilometers) wide, with lava flows carving long, winding canals up to more than 3,000 miles (5,000 km) in length, longer than on any other planet.

Six mountainous regions make up about one-third percent of the Venusian surface. One mountain range, called Maxwell, is about 540 miles (870 km) long and reaches up to some 7 miles (11.3 km) high, making it the highest feature on the planet.

Venus also possesses a number of surface features unlike anything on Earth. For example, Venus has coronae, or crowns — ringlike structures that range from roughly 95 to 360 miles (155 to 580 km) wide. Scientists believe these formed when hot material beneath the crust rises up, warping the planet’s surface. Venus also has tesserae, or tiles — raised areas in which many ridges and valleys have formed in different directions.

With conditions on Venus that could be described as infernal, the ancient name for Venus — Lucifer — seems to fit. However, this name did not carry any fiendish connotations; Lucifer means "light-bringer," and when seen from Earth, Venus is brighter than any other planet or even any star in the night sky because of its highly reflective clouds and its closeness to our planet.

Venus takes 243 Earth days to rotate on its axis, by far the slowest of any of the major planets, and because of this sluggish spin, its metal core cannot generate a magnetic field similar to Earth's.

Orbital characteristics

If viewed from above, Venus rotates on its axis the opposite way that most planets rotate. That means on Venus, the sun would appear to rise in the west and set in the east. On Earth, the sun appears to rise in the east and set in the west.

The Venusian year — the time it takes to orbit the sun — is about 225 Earth days long. Normally, that would mean that days on Venus would be longer than years. However, because of Venus' curious retrograde rotation, the time from one sunrise to the next is only about 117 Earth days long. [Gallery: Transit of Venus from June 5, 2012, when the planet transited in front of the sun for the last time until the year 2117.

Venus, second planet from the sun, is one of the brightest natural objects in the sky and has been considered Earth’s sister planet.

Composition & structure

Atmospheric composition (by volume): 96.5 percent carbon dioxide, 3.5 percent nitrogen, with minor amounts of sulfur dioxide, argon, water, carbon monoxide, helium and neon.

Magnetic field: 0.000015 times that of Earth's field.

Internal structure: Venus' metallic iron core is roughly 2,400 miles (6,000 km) wide. Venus' molten rocky mantle is roughly 1,200 miles (3,000 km) thick. Venus' crust is mostly basalt, and is estimated to be six to 12 miles (10 to 20 km) thick on average.

Orbit & rotation

Average distance from the sun: 67,237,910 miles (108,208,930 km)
By Comparison: 0.723 times that of Earth

Perihelion (closest approach to sun): 66,782,000 miles (107,476,000 km)
By Comparison: 0.730 times that of Earth

Aphelion (farthest distance from sun): 67,693,000 miles (108,942,000 km)
By Comparison: 0.716 times that of Earth

Climate

The very top layer of Venus' clouds zip around the planet every four Earth days, propelled by hurricane-force winds traveling roughly 224 mph (360 kph). This super-rotation of the planet's atmosphere, some 60 times faster than Venus itself rotates, may be one of Venus' biggest mysteries. The winds at the planet's surface are much slower, estimated to be just a few miles per hour.

The Venus Express spacecraft the European Space Agency launched in 2005 intriguingly found evidence of lightning on the planet. This lightning is unique from that found on the other planets in the solar system that possess it, in that it is the only lightning known that is not associated with water clouds. Instead, on Venus, the lightning is associated with clouds of sulfuric acid. Scientists are excited by these electrical discharges, because they can break molecules into fragments that can then combine with other fragments in unexpected ways.

Unusual stripes in the upper clouds of Venus are dubbed "blue absorbers" or "ultraviolet absorbers" because they strongly absorb light in the blue and ultraviolet wavelengths. These are soaking up a huge amount of energy — nearly half of the total solar energy the planet absorbs. As such, they seem to play a major role in keeping Venus as hellish as it is. Their exact composition remains uncertain.

Research & exploration

The United States, Soviet Union and European Space Agency have deployed many spacecraft to Venus, more than 20 in all so far. NASA's Mariner 2 came within 21,600 miles (34,760 km) of Venus in 1962, making it the first planet to be observed by a passing spacecraft. The Soviet Union's Venera 7 was the first spacecraft to land on another planet, and Venera 9 returned the first photographs of the Venusian surface. The first Venusian orbiter, NASA's Magellan, generated maps of 98 percent of the planet's surface using radar, showing details of features as small as 330 feet (100 meters) across.

The European Space Agency's Venus Express is now in orbit around Venus with a large variety of instruments, and has confirmed the presence of lightning there. The next mission to Venus, Japan's Akatsuki, was launched in 2010, and will follow Venus' thick cloud layers as they are whipped around the planet by hurricane-force winds.

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Further reading:

NASA Solar System Exploration: Venus Overview

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