Venus Planet statistics Distance from the Sun (in millions) Maximum: 67.6 miles 108.9 km 0.728 AU Minimum: 66.7 miles 107.4 km 0.718 AU Mean: 67.2 miles 108.2 km 0.723 AU Revolution period ("one year"): 224.7 days Rotation period (equatorial): 243 days (retrograde) Mean orbital velocity per second: 21.8 miles (35 km) Inclination of axis: 178 Orbital eccentricity: 0.007 Orbital inclination: 3.39 degrees Diameter at equator: 7,523 miles 12,104 km 0.95 x Earth's diameter Oblateness: 0.006 Escape velocity per second: 6.4 miles (10.4 km) Mean surface temperature: 896F / 480C / 753░ K Mass: 4.87 x 10^24 kg (Earth = 1): 0.815 Volume (Earth =1): 0.86 Density (water = 1): 5.24 g/cm^3 Surface gravity: 5.24 m/s^2 (Earth = 1): 0.90 Maximum apparent diameter as seen from Earth (seconds of arc): 65".2 Mean diameter of Sun as seen from the planet: 44' 15" Albedo: 0.76 Oblateness: 0 Number of known moons: 0 Planet composition Researchers believe that Venus, which is almost perfectly spherical, has a liquid iron core that is smaller than the Earth's. Researchers also believe that Venus' relatively static, rocky crust may be composed of a single plate. The soil samples taken by Veneras 9 and 10 have a composition similar to terrestrial ocean deposits, but the origin is unknown. (They do not appear to be volcanic.) Compared with the Earth, Venus has a similar interior structure, an almost-equal diameter, 80% of the mass, but only 2% of the density. [Rick: Here are the composition figures we found. You might want to compare these to figures you have.] Core = 5,500 - 6,200 km in diameter Mantle = 2,956 km thick Crust = 25 km thick Topography The topography of Venus is diverse. A series of large (up to 150 km in diameter) but shallow craters populate the surface. There are also highlands (average elevation of 3 km) and a system of faults. The two large highlands areas are Ishtar Terra, in the northern hemisphere, and Aphrodite Terra, slightly to the south of the equator. Ishtar Terra is about the size of Australia, and its highest point (11 km) occurs in a grouping known as the Maxwell Mountains. Aphrodite Terra is about the size of Africa and its highest point is 7 km. Diana Chasma is Venus' largest valley, lying about 4 km below the surrounding ridges. The largest basin is Atlanta Planitia, which is comparable in size to the Gulf of Mexico. Atmosphere The Venusian atmosphere is composed primarily of carbon dioxide (96%). Nitrogen, sulpher dioxide, hydrogen chloride, hydrogen fluoride, carbon monoxide, and very little water vapor are also present. Broad bands of clouds composed of sulphuric acid droplets and solid particles also surround the planet. The equatorial band is composed of fine streams of cloud, and Y- and C-shaped formations, and each pole is shrouded with spiraling clouds that connect the equatorial bands. At some level underneath the clouds, there are lightening storms. Venera 11 and 12 both detected several minutes of electromagnetic signals thought to be similar to terrestrial lightning storms. Venera 11 also detected a noise level that could have been thunder. Venus has a hot, dry climate now, but perhaps was hospitable at one time. In fact, researchers believe it may have been covered by an ocean of water. Today, intense heat from the Sun keeps the mean surface temperature at 896░ F / 480░ C / 753░ K. The thick atmosphere and ionosphere surrounding Venus protects the planet's surface from solar winds, but also retains the intense heat, producing the greenhouse effect. At the surface of Venus, the atmospheric pressure is 90 times greater than Earth's. At a 50 km elevation, pressure reaches 1 atmosphere (the mean sea-level pressure on Earth). The atmosphere surrounding Venus contains greater amounts of both argon isotopes (Ar-38 and Ar-36) than the Earth's atmosphere, but a smaller amount of Ar-40, which is caused by the radioactive decay of potassium. Venus' atmosphere also contains three times more krypton and nitrogen and much more carbon dioxide than Earth's. The magnetosphere displays several plasma effects, but there are no bands of trapped particles as there are surrounding Earth. Magnetic fields and gravity There is no detectable magnetic field on Venus. The gravity at the surface of Venus is 0.902. The planet's specific gravity is 5.2. [***Rick: You mentioned in our last meeting that one of your sources says there is a magnetic field. You may want to revise the paragraph above to reflect that source.***] Orbit and rotation Venus has the most circular orbit of any planet. Its rotation is also unique: First, it takes longer for the planet to rotate on its axis than it takes to orbit the Sun. (The globe rotation is at the equator is 243 days, whereas the planet's year is only 224.7 days.) Second, Venus rotates east to west, which is retrograde (backward) from that of the Sun and most other planets. Finally, it's interesting to note that Venus' upper atmosphere rotates around the planet in only four days, while the planet itself takes 243 days to complete one revolution. Moons and/or rings Venus is so bright it sometimes produces a ghost image. Astronomers in the 17th and 18th centuries thought the image to be a satellite, but it has since been confirmed that there are no satellites associated with Venus. Mythology Venus has been known for centuries. The ancient Babylonians named it Nin-dar-Anna, "Mistress of the Heavens;" the Chinese, Tai-pe, "The Beautiful White One;" the Greeks, Hesperus, the "Evening star," and Phosphorus, the "Morning star." The planet is named for the Roman goddess of love and beauty, and astrologers believed that any child born under the rays of Venus would be blessed with those features. Venus was the symbol of gentleness and charm, a taste for music, harmony, playfulness, and generosity. Friday, in ancient times, was dedicated to Venus. Discovery and exploration Galileo first viewed Venus close-up using an "optick tube" in 1610. In the eighteenth century, J.H. Schroeter confirmed the existence of an atmosphere. In the nineteenth century, imaginative speculation regarding possible life forms on Venus abounded, fueled by the fictional writings of Jules Verne. Illustrations of Venusian creatures appeared in many popular magazines of the day. No life, however, has ever been found on the planet. Because of the atmosphere, direct photography of Venus' surface is impossible. The only method of exploring the planet from Earth is by using radar. In recent years, the US and former USSR have sent many missions to explore Venus, including: The Mariner missions, begun in December 1962 by the US. The Venera missions, begun in February 1966 by the USSR. The Pioneer missions, begun in 1978 by the US. The Magellan missions, begun in 1989 by the US.
