Venus

Image of Venus. Credit: NASA
Image of Venus. Credit: NASA

Venus and Earth are similar in size, mass, density, composition and gravity. There, however, the similarities end. Venus is covered by a thick, rapidly spinning atmosphere, creating a scorched world with temperatures hot enough to melt lead and a surface pressure 90 times that of Earth.

The Venusian year (orbital period) is about 225 Earth days long, while the planet’s sidereal rotation period is 243 Earth days, making a Venus solar day (measured noon to noon) about 117 Earth days long. Resulting from this slow rotation Venus cannot generate a magnetic field similar to Earth’s — though its core iron content is similar to that of the Earth. (Venus’ iron core is approximately 3,000 km [1,900 miles] in radius.) Venus rotates retrograde (east to west) compared with Earth’s prograde (west to east) rotation. Seen from Venus, the sun would rise in the west and set in the east.

Because of its proximity to Earth and the way its clouds reflect sunlight, Venus appears to be the brightest planet in the sky. Although we cannot normally see through Venus’ thick atmosphere, NASA’s Magellan mission to Venus during the early 1990s used radar to image 98 percent of the surface, and the Galileo spacecraft used infrared mapping to view mid-level cloud structure as it passed by Venus in 1990 on its way to Jupiter.

Like Mercury, Venus can be seen periodically passing across the face of the sun. These transits of Venus occur in pairs with more than a century separating each pair. Since the telescope was invented, transits were observed in 1631, 1639; 1761, 1769; and 1874, 1882. On 8 June 2004, astronomers worldwide saw the tiny dot of Venus crawl across the sun; the second in this pair of early 21st-century transits occurred 6 June 2012.

Venus’ atmosphere consists mainly of carbon dioxide, with clouds of sulfuric acid droplets. Only trace amounts of water have been detected in the atmosphere. The thick atmosphere traps the sun’s heat, resulting in surface temperatures higher than 880 degrees Fahrenheit (471 degrees Celsius). Probes that have landed on Venus survived only a few hours before being destroyed by the incredible temperatures. Sulfur compounds are abundant in Venus’ clouds. The corrosive chemistry and dense, moving atmosphere cause significant surface weathering and erosion.

As Venus moves forward in its solar orbit while slowly rotating backwards on its axis, the top level of cloud layers zips around the planet every four Earth days, driven by hurricane-force winds traveling at about 360 km (224 miles) per hour. The wind speeds within the clouds decrease with cloud height, and winds at the surface are estimated to be just a few kilometers per hour. How this atmospheric super-rotation forms and is maintained continues to be a topic of scientific investigation.

Atmospheric lightning bursts, long suspected by scientists, were finally confirmed in 2007 by the European Venus Express orbiter. On Earth, Jupiter and Saturn, lightning is associated with water clouds, but on Venus, it is associated with clouds of sulfuric acid.

Radar images of the surface show wind streaks and sand dunes. Craters smaller than 1.5 to 2 km (0.9 to 1.2 miles) across do not exist on Venus because small meteors burn up in the dense atmosphere before they reach the surface.

It is thought that Venus was completely resurfaced by volcanic activity 300 to 500 million years ago. More than 1,000 volcanoes or volcanic centers larger than 20 km (12 miles) in diameter dot the surface. Volcanic flows have produced long, sinuous channels extending for hundreds of kilometers. Venus has two large highland areas: Ishtar Terra, about the size of Australia, in the north polar region; and Aphrodite Terra, about the size of South America, straddling the equator and extending for almost 10,000 km (6,000 miles). Maxwell Montes, the highest mountain on Venus and comparable to Mount Everest on Earth, is at the eastern edge of Ishtar Terra.

Discovered By
Known by the Ancients
Date of Discovery
Unknown
Orbit Size Around Sun (semi-major axis)
Metric: 108,209,475 km
English: 67,238,251 miles
Scientific Notation: 1.0820948 x 108 km (7.2333566 x 10-1 A.U.)
By Comparison: 0.723 x Earth
Perihelion (closest)
Metric: 107,476,170 km
English: 66,782,596 miles
Scientific Notation: 1.07476 x 108 km (7.184 x 10-1 A.U.)
By Comparison: 0.731 x Earth
Aphelion (farthest)
Metric: 108,942,780 km
English: 67,693,905 miles
Scientific Notation: 1.08943 x 108 km (0.7282 A.U.)
By Comparison: 0.716 x Earth
Sidereal Orbit Period (Length of Year)
0.61519726 Earth years
224.70 Earth days
By Comparison: 0.615 x Earth
Orbit Circumference
Metric: 679,892,378 km
English: 422,465,538 miles
Scientific Notation: 6.799 x 108 km
By Comparison: 0.723 x Earth
Average Orbit Velocity
Metric: 126,074 km/h
English: 78,339 mph
Scientific Notation: 3.5020 x 104 m/s
By Comparison: 1.176 x Earth
Orbit Eccentricity
0.00677672
By Comparison: 0.406 x Earth
Orbit Inclination
3.39 degrees
Equatorial Inclination to Orbit
177.3 degrees (retrograde rotation)
By Comparison: 7.56 x Earth
Mean Radius
Metric: 6,051.8 km
English: 3,760.4 miles
Scientific Notation: 6.0518 x 103 km
By Comparison: 0.9499 x Earth
Equatorial Circumference
Metric: 38,024.6 km
English: 23,627.4 miles
Scientific Notation: 3.80246 x 104 km
By Comparison: 0.9499 x Earth’s
Volume
Metric: 928,415,345,893 km3
English: 222,738,686,740 mi3
Scientific Notation: 9.28415 x 1011 km3
By Comparison: 0.857 x Earth’s
Mass
Metric: 4,867,320,000,000,000,000,000,000 kg
Scientific Notation: 4.8673 x 1024 kg
By Comparison: 0.815 x Earth
Density
Metric: 5.243 g/cm3
By Comparison: Comparable to the average density of the Earth.
Surface Area
Metric: 460,234,317 km2
English: 177,697,463 square miles
Scientific Notation: 4.6023 x 108 km2
By Comparison: 0.902 x Earth
Surface Gravity
Metric: 8.87 m/s2
English: 29.1 ft/s2
By Comparison: If you weigh 100 pounds on Earth, you would weigh 91 pounds on Venus.
Escape Velocity
Metric: 37,296 km/h
English: 23,175 mph
Scientific Notation: 1.036 x 104 m/s
By Comparison: 0.926 x Earth
Sidereal Rotation Period (Length of Day)
-243.018 Earth days (retrograde)
-5832.4 hours (retrograde)
By Comparison: 243.68 x Earth
Minimum/Maximum Surface Temperature
Metric: 462 °C
English: 864 °F
Scientific Notation: 735 K
Atmospheric Constituents
Carbon Dioxide, Nitrogen
Scientific Notation: CO2, N2
By Comparison: Earth’s atmosphere consists mostly of N2 and O2.
CO2 is largely responsible for the Greenhouse Effect and is used for carbonation in beverages.
N2 is 80% of Earth’s air and is a crucial element in DNA.