- Diameter: 12,104 km
- Mass: 4.87 x 10^24 kg (81.5% Earth)
- Moons: None
- Orbit Distance: 108,209,475 km (0.73 AU)
- Orbit Period: 225 days
- Surface Temperature: 462 °C
- First Record: 17th century BC (Babylonian astronomers_)
- A day on Venus lasts longer than a year. It takes 243 Earth days to rotate once on its axis (sidereal day). The planet’s orbit around the Sun takes 225 Earth days, compared to the Earth’s 365. A day on the surface of Venus (solar day) takes 117 Earth days.
- Venus rotates in the opposite direction to most other planets. This means that Venus is rotating in the opposite direction to the Sun, this is also known as a retrograde rotation. A possible reason might be a collision in the past with an asteroid or other object that caused the planet to alter its rotational path. It also differs from most other planets in our solar system by having no natural satellites.
- Venus is the second brightest object in the night sky. Only the Moon is brighter. With a magnitude of between -3.8 to -4.6 Venus is so bright it can be seen during daytime on a clear day.
- Atmospheric pressure on Venus is 92 times greater than the Earth’s. While its size and mass are similar to Earth, the small asteroids are crushed when entering its atmosphere, meaning no small craters lie on the surface of the planet. The pressure felt by a human on the surface would be equivalent to that experienced deep beneath the sea on Earth.
- Venus is often called the Earth’s sister planet. The Earth and Venus are very similar in size with only a 638 km difference in diameter, Venus having 81.5% of the Earth’s mass. Both also have a central core, a molten mantle and a crust.
- Venus is also known as the Morning Star and the Evening Star. Early civilizations thought Venus was two different bodies, called Phosphorus and Hesperus by the Greeks, and Lucifer and Vesper by the Romans. This is because when its orbit around the Sun overtakes Earth’s orbit, it changes from being visible after sunset to being visible before sunrise. Mayan astronomers made detailed observations of Venus as early as 650 AD.
- Venus is the hottest planet in our solar system. The average surface temperature is 462 °C, and because Venus does not tilt on its axis, there is no seasonal variation. The dense atmosphere of around 96.5 percent carbon dioxide traps heat and causes a greenhouse effect.
- A detailed study of Venus finished in 2015. In 2006, the Venus Express space craft was sent into orbit around Venus by the European Space Agency, and sent back information about the planet. Originally planned to last five hundred Earth days, the mission was extended several times before the craft was finally deorbited in 2015. More than 1,000 volcanoes or volcanic centres larger than 20 km have been found on the surface of Venus.
- The Russians sent the first mission to Venus. The Venera 1 space probe was launched in 1961, but lost contact with base. The USA also lost their first probe to Venus, Mariner 1, although Mariner 2 was able to take measurements of the planet in 1962. The Soviet Union’s Venera 3 was the first man-made craft to land on Venus in 1966.
- At one point it was thought Venus might be a tropical paradise. The dense clouds of sulphuric acid surrounding Venus make it impossible to view its surface from outside its atmosphere. It was only when radio mapping was developed in the 1960s that scientists were able to observe and measure the extreme temperatures and hostile environment. It is thought Venus did once have oceans but these evaporated as the planets temperature increased. © Space Facts. com
Atmosphere Venus’ atmosphere can be divided into two broad layers. The first is the cloud bank that effectively encases the entire planet. The second is everything below these clouds. The clouds surrounding Venus extend from 50 to 80 kilometers above the planet’s surface and are composed primarily of sulphur dioxide (SO2) and sulphuric acid (H2SO4). These clouds are so dense that they reflect 60% of the sunlight Venus receives back into space. When studying the sub-cloud atmosphere two features are immediately prominent: density and composition. Furthermore, the effect these two features produce on the planet is profound, making Venus the hottest and least hospitable of any planet in the Solar System. With an atmospheric density of approximately 480° C, this easily makes Venus’ surface the hottest of any planet’s in the solar system.
Surface Due to the thick clouds enshrouding Venus, the details of its surface cannot be obtained through simple photographic means. Fortunately, scientists have been able to use the method of radar mapping to acquire this information instead. While both photography and radar imaging work by collecting radiation that has bounced off an object, the difference lies in the forms of radiation collected. Photography collects visible light radiation, and radar mapping collects microwave radiation. The advantage in using radar mapping with Venus is that microwave radiation is able to pass through the planet’s thick clouds, whereas the light necessary for photography is unable to do so. The first radar mappings of the Venusian surface via spacecraft came in 1978 when the Pioneer Venus spacecraft began orbiting the planet. What the resulting maps revealed was a surface consisting primarily of plains formed by ancient lava flows, with only two highland regions, Ishtar Terra and Aphrodite Terra. In 1990, the Magellan spacecraft began orbiting Venus. In addition to performing radar mapping similar to that of Pioneer Venus, Magellan also undertook a more advanced radar imaging that gathered much finer details. What Magellan found was approximately 1000 impact craters. Interestingly, none of the craters seen were less than 2 km in diameter. This suggest that any meteroid small enough to create a crater having a diameter less than 2 km would have broken apart and burned up during its passage through the dense Venusian atmosphere. An additional observation regarding the size of the impact craters helped to shed light on the age of the planet’s surface. Not only were small impact craters absent on the planet’s surface, but also those of large diameter. What this tells us is that the surface has been formed since the period of heavy bombardment, a span of 3.8 to 4.5 billion years ago when a large number of impact craters were formed on the inner planets. Thus, geologically speaking, the Veunsian surface is relatively young. Finally, the surface’s most prominent features are those produced by the planet’s volcanic activity. As noted above, the first of these features is the enormous plains caused by ancient lava flows. Covering over 80% of the Venusian surface, these plains are the most dominant feature. The second prominent feature is the surface’s volcanic structures, which are numerous and varied. In addition to shield volcanoes similar to those found on Earth (e.g., Mauna Loa), many “pancake” volcanoes have been observed on Venus. These volcanoes, unlike any on Earth, are believed to have formed their distinctive flat, disc-like shape due to an eruption of all of the volcano’s lava at once through a single vent. After such an eruption, the lava then spreads outwardly in a uniform, circular manner.
Interior As with the other terrestrial planets, Venus’ interior is essentially composed of three layers: a crust, a mantle, and a core. However, what is intriguing about Venus’ interior (as opposed to that of Mercury or Mars) is how alike it is to the Earth’s interior. While it is impossible to test the true similarity of the two planets’ interiors, it is reasonable to draw such conclusions based on the characteristics the two planets are known to share. Hence, it is believed that Venus’ crust is 50 km thick, its mantle 3,000 km thick, and the core has a diameter of 6,000 km. An unanswered question about the Venusian interior is whether or not the planet’s core is liquid or solid. On one hand, because Venus and Earth are so alike, it is reasonable to conclude that since Earth has a liquid core, Venus does as well. On the other hand, there is also evidence to suggest the Venusian core is solid. This evidence stems from the planet’s lacking a substantial magnetic field. Simply put, planetary magnetic fields are a result of the transfer of heat from inside a planet to its surface. A necessary component of this transfer is a liquid core. The argument is since Venus lacks a substantial magnetic field, it cannot possess a liquid core.
Orbit & Rotation The most notable aspect of Venus’ orbit is its uniformity of distance from the Sun. Indeed, with an eccentricity of only .00678, Venus’ orbit is easily the most circular of all the planets. Moreover, this small eccentricity means that the difference between Venus’ perihelion (1.07 x 108 km) and its aphelion (1.09 x 108 km) is a mere 1.46 x 106 km. Like information regarding Venus’ surface, little data about its rotation could be obtained until the radar imaging missions of the second half of the twentieth-century. Surprisingly, what these missions revealed was just how unique Venus’ rotation is. Whereas the standard rotation for a planet about its axis is counterclockwise (as viewed from the “top” of the orbital plane), Venus’ rotation is retrograde or clockwise. The reason for this is presently unknown, but there are two popular theories. The first points to the 3:2 spin-orbit resonance of Venus with the Earth. To some, this is highly suggestive that over billions of years the Earth’s gravitational force has altered Venus’ rotation to its present state. Some scientists, however, doubt that the Earth’s gravitational force has been great enough to change Venus in such a fundamental way. Instead, they have looked to the early Solar System when the planets were being formed to provide an explanation. They theorize that Venus’ original rotation was similar to that of the other planets’, yet it was altered to its current orientation when a large planetesimal struck the young planet with great force, essentially knocking the planet upside down. A second unexpected discovery regarding Venus’ rotation is its speed. Taking approximately 243 Earth days to complete a single rotation, a day on Venus is longer than on any other planet. This alone is noteworthy. What is even more striking, though, is when Venus’ day is compared to its year. At roughly 224 earth days, Venus’ year is almost 19 earth days less than one Venusian day. Again, no other planet shares such a property. The leading theory for this phenomenon is that which is used to explain the planet’s retrograde rotation. © The Planets.org