Everything We Should Know About VENUS, OUR PLANETARY NEIGHBOR....
VENUS (The Evening Star)
Venus is the second planet from the Sun and is the brightest planet in the solar system. It is sometimes referred to as the sister planet to Earth, because of the similar mass and size. The planet is named after the Roman goddess of love and beauty. In this article, we will be discussing the characteristics and a few astonishing facts of Venus.
Discovery of Venus
Venus is the brightest planet and is easily noticeable with unaided eyes. Ancient people likely knew about it. One of the earliest Babylonian astronomical documents speaks about Venus. Galileo Galilei was the first person to aim a telescope at Venus in 1600. The first aircraft to visit Venus was NASA’s Mariner 2 in 1962. Most recently, NASA’s Magellan visited Venus and mapped out the surface with the help of radar.
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Due to slow rotation on its axis, it takes 243 Earth days to complete one rotation. The orbit of the planet takes 225 Earth days making a year on Venus shorter than a day.
Though it has been visually observable for as long as mankind can remember, the naming of Venus is again a bit of a mystery. Venus received its most popular moniker via a selection of Roman gods and goddesses. Venus was named after the Roman goddess of love and beauty, a counterpart to Greek’s Aphrodite. It wasn’t always known as such. Ancient Babylonians who recognized Venus for example, named it as the Star of Ishtar, their own goddess of fertility, love and war.
The symbol for womanhood has even been adopted as the symbol of this planet of love and strong women, being the first and only one with a feminine name. Prior to being officially dubbed Venus, Greeks and Romans had unknowingly turned Venus into two different stars.
To the Greeks, Venus was both Phosphorus and Hesperus and to the Romans, it was recognized as Lucifer and Vesper. Both nations didn’t know that the alleged two stars they were referencing was actually one body until later when further observations were conducted and its orbit was understood.
Formation
It is theorized that Venus was formed about 4.5 billion years ago when gravity pulled swirling gas and dust together to form the second planet and it later settled into its current layout.
Distance, Size and Mass
Venus is the second closest planet to the Sun, at a distance of 108.2 million km/ 67.24 mi or 0.7 AU receiving the sun’s light in 6 minutes. Venus has a radius of 6.051 km or 3.760 miles and a diameter of 12.104 km or 7.521 mi, slightly smaller than Earth.
It has a mass of 4.87 × 1024 kg, or 85% that of Earth. The mentioned similarities also give way to similar densities, Venus having a density of 5.24 grams per cubic centimeter, while Earth has 5.52. It also has a as much volume as Earth - 928.45 billion cubic km compared to Earth's 1083.21 billion.
Its closest approach to Earth happens once every 584 days, when the planets catch up to one another. On average it can get as close as 25 million miles or 40 million kilometers to Earth the equivalent of about 0.28 AU.
Orbit
One of the reasons that ancient civilizations unknowingly turned Venus into two separate stars – The Mourning Star and The Evening Star - was that they didn’t understood its orbit. Venus goes from being visible only after sunset to only being visible prior to sunrise when its orbit around the sun surpasses Earth’s orbit.
Venus orbits the Sun at an average distance of about 0.72 AU and completes an orbit every 224.7 days. Though most planetary orbits are elliptical, Venus’s orbit is the closest to circular with an eccentricity of less than 0.01. When Venus lies between Earth and the Sun in inferior conjunction, it makes the closest approach to Earth of any planet at a distance of 41 million km or 25 million miles. Venus spends most of its time away from Earth. This paradoxically makes Mercury the closest planet to Earth, a plurality of the time.
The orbit is a bit inclined relative to Earth’s orbit. When Venus passes between Earth and the Sun, it usually doesn’t cross the face of the Sun.
Transits of Venus occur when the planet’s inferior conjunction coincides with its presence in the plane of Earth’s orbit.
Transits of Venus occur in cycles of 243 years with the current pattern of transits being pairs of transits separated by eight years, at intervals of about 105.5 years or 121.5.
Pentagram of Venus
When plotted geocentrically – from an Earth centered perspective, there is a highly noticeable rhythm in the motion of Venus. After 8 years, it returns to the same place in the sky on the same date.
This was known to many ancient civilizations such as the Maya, it is termed the pentagram of Venus.
Over eight years, each phenomenon – each relative position of Earth, Venus, and the Sun – occurs five times, and then over the next eight years they repeat five times almost identically. Citations and credits – Guy Ottewell – Earthsky.
Rotation
Venus has a retrograde rotation, moving in the opposite direction than most planets, only Uranus also does this. They both move from East to West, clockwise. Venus does this rotation once every 243 Earth days, having the slowest rotation out of all the planets in the solar system.
This slow rotation also influences its shape, making Venus very spherical. One Venusian day is longer than one Venusian year – 225 Earth days. As a comparison, Venus’s equator rotates at 6.52 km/h while Earth’s rotates at 1,674.4 km/h.
It has been observed that it’s even getting slower. In 16 years between the Magellan spacecraft and Venus Express visits, the rotation of Venus has slowed down up to 6.5 minutes in that time span.
Theories suggest that this slow and retrograde rotation are due to the fact that Venus suffered a collision in the past as, while some consider it as an equilibrium state between tidal locking to the Sun’s gravitation, which tends to slow rotation, and an atmospheric tide created by solar heating of the thick Venusian atmosphere.
Axial tilt
Venus has tilted away from the plane of the ecliptic by 2.7 degrees meaning it is almost completely upside down. Because of this, Venus almost doesn’t experience any seasons spinning nearly upright.
Structure and Geology
Venus is very similar to Earth in its structure. The core is posseses is approximately 2.000 miles or 3.200 kilometers in radius. Above that core rests a mantle of hot rock, slowly churning due to the planet’s interior heat. As a result the surface is a thin crust of rock that bulges and moves as Venus’s mantle shifts, and creates volcanoes.
Its core is at least partially liquid since both Venus and Earth started cooling at about the same rate. Due to its smaller size, it is estimated that Venus’s pressure is about 24% lower in its deep interior.
About 80% of the Venusian surface is covered by smooth, volcanic plains, consisting of 70% plains with ridges and 10% smooth or lobate plains. Venus does contain two highland “continents” that make up the rest of its surface area. One is located in the planet’s northern hemisphere and it is called Ishtar Terra after Ishtar, the Babylonian goddess of love, and it is about the size of Australia.
The highest mountain on Venus is named Maxwell Montes and it is located here, its peak is about 11 kilometers or 7 miles above the Venusian average surface elevation.
The second “continent” is located in the southern hemisphere, south of the equator, and it is called Aphrodite Terra, after the Greek goddess of love. It is the larger of the two highlands, at a roughly size of South America. Here there is a network of fractures and faults that covers much of the area. What is an enigma is the absence of evidence of lava flow and calderas.
With few and small impact craters, it is suggested that Venus’s dense atmosphere burns up smaller meteors, and in the same time it indicates that its surface is young. As far as we know, Venus doesn’t have tectonic activity like Earth.
It is believed that water helps drive that, and Venus long ago lost its water because of the greenhouse effect. The surface even though it appears young, has craters that appear equally eroded that point towards a catastrophic event that resurfaced the planet about half a billion years ago. All features that were older were wiped out, and big impacts over time created these new young craters.
It is believed that the volcanoes on the surface of Venus repaved the planet. There are many indirect evidences that volcanic activity is ongoing to this day. Sulfur dioxide level dropped in 1980, which may indicate that a big volcanic event happened in 1870, blasting out lots of gas, which then subsided.
It is theorized that without tectonics, slow bubbling leaks of lava from the interior of the planet can continue in one spot for a long time creating what is called as “pancake domes.”
Atmosphere
The atmosphere consists mainly of carbon dioxide 96.5% and 3.5% nitrogen with traces of other gases, most notably sulfur dioxide. Venus has thick clouds mainly composed of sulfuric acid droplets, around 75-96%.
This thick atmosphere traps the Sun’s heat, reflecting 75% of the sunlight that falls on them. This atmosphere results in surface temperatures higher than 465 degrees Celsius, 900 degrees Fahrenheit, hot enough to melt lead. The mass of this atmosphere is 93 times greater than that of Earth, a pressure equivalent to that at a depth of nearly 1 kilometer or 0.62 miles under the ocean.
The density at the surface is 65 kg/m3, 6.5% that of water or 50 times as dense as Earth's atmosphere at 293 K (20 °C; 68 °F) at sea level.
Despite its slow rotation, strong 300 km/h (185 mph) winds at the cloud tops go around Venus about every four to five Earth days. Winds on Venus move at up to 60 times the speed of its rotation, whereas Earth's fastest winds are only 10–20% rotation speed.
Speeds within the clouds decrease with cloud height, and at the surface are estimated to be just a few miles per hour.
The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about 655 K (380 °C; 715 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).
Magnetosphere
Regardless of Venus’s similar size to Earth, and its similarly sized iron core, the magnetic field is much weaker than that of Earth’s due to slow rotation and thus it is generally regarded as not having a magnetosphere.
It does have however, an induced magnetosphere formed by the Sun’s magnetic field carried by solar wind.
Because of the lack of intrinsic magnetic field on Venus, the solar wind penetrates relatively deep into the planetary exosphere and causes substantial atmosphere loss. The loss happens mainly via the magnetosphere’s tail. The ratio of hydrogen to oxygen losses is around 2 or almost stoichiometric, indicating the ongoing loss of water.
Life Habitability
It is widely believed that Venus was once a habitable planet with vast oceans, some even considered that life might have actually evolved there and later shifted somehow to Earth. Others believe that Venus possessed oceans, but due to the high concentration of carbon dioxide in the atmosphere, it is theorized that the planet was covered in a carbon dioxide fluid that eventually evaporated.
Recently it has been discovered that Venus has a large vortex at both its poles. The altitude is estimated to be about 59 km which is just above the cloud deck and the air pressure and temperature are tolerable for Earth standards. A few scientists have speculated that thermoacidophilic extremophile microorganisms might exist in the lower-temperature, acidic upper layers of the Venusian atmosphere.
In August 2019, astronomers reported that newly discovered long-term pattern of absorbance and albedo changes in the atmosphere of the planet Venus are caused by "unknown absorbers", which may be chemicals or even large colonies of microorganisms high up in the atmosphere of Venus, it remains to be seen.
Satellites
Theories suggest that Venus might once have had a moon, which formed after a collision. After this, a second collision occurred that shattered the moon. It is believed that even this moon actually collided into Venus thus its unusual rotation.
Future plans for Venus
Venus being so close to us has seen over 40 spacecraft’s landing upon her. Due to its proximity it will always be a target for future studies and even possible colonization. Scientists have even discussed about “floating cities” in Venus. Missions are still ongoing there, even recently in November 2019, NASA received some designs of a stingray-like-ship that could better observe and analyze Venus by a team at the University at Buffalo.
Did you know?
- Temperatures remain the same on Venus regardless of day and night.
- Venus may appear as a white point of light in the sky, it has an apparent magnitude of -4.14 with a standard deviation of 0.31. It can be seen even in a clear midday sky, and it is more easily visible when the Sun is low on the horizon or setting.
- Venus always lies 47 degrees of the Sun.
- Earth orbits the sun 8 times for every 13 orbits of Venus.
- Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over 100 km (62 mi) across.
- The Venus tablet of Ammisaduqa, believed to have been compiled around the mid-seventeenth century BCE, shows the Babylonians understood that the Evening Star and Morning Star were a single object, referred to in the tablet as the "bright queen of the sky", and could support this view with detailed observations.
- Chinese people historically referred to the morning Venus as “The Great White” or “the Opener of Brightness”, and the evening Venus as “the Excellent West One.”
- Though Americans were the first on the Moon, Russian’s were the first to send an unmanned spacecraft to Venus in 1967. The spacecraft was named Venera 4, many other spacecraft’s with the same name but different numbers were sent after.
- Spacecraft’s sent to Venus didn’t last more than an hour due to the crushing atmosphere and harsh conditions.
- Out of the four terrestrial planets, Venus is the second largest.
- Venus is the first planet in the Solar System to have its orbit plotted in the sky by ancient civilizations.
- Venus has been a primary feature throughout mythology and fiction. Classic poets such as Homer, Sappho and Virgil have written about the planet. It has also been included in The Starry Night by Vincent van Gogh.
- Mercury and Venus orbit the Sun within Earth’s Orbit, this makes them inferior planets.
Facts about Venus
- Venus does not have any moons or rings.
- Venus is nearly as big as the Earth with a diameter of 12,104 km.
- Venus is thought to be made up of a central iron core, rocky mantle and silicate crust.
- A day on the surface of Venus (solar day) would appear to take 117 Earth days.
- A year on Venus takes 225 Earth days.
- The surface temperature on Venus can reach 471 °C.
- 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. One possible reason for this might be a collision with an asteroid or other object. - 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.
Due to this crushing small asteroids when they enter its atmosphere Venus has not small craters. The pressure felt on Venus’ surface is equivalent to that 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 and Venus having 81.5% of the Earth’s mass. Both also have a central core, a molten mantle and a crust. - The same side of Venus always faces the Earth when at their closest.
It is possible this is due to the Earth’s gravational influence. - Venus is also known as the Morning Star and the Evening Star.
Early civilisations thought Venus was two different bodies. These were called Phosphorus and Hesperus by the Greeks, and Lucifer and Vesper by the Romans. When Venus’ 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. Originally planned to last five hundred Earth days, the mission was extended several times before the craft was 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 the extreme temperatures and hostile environment.
Venus Diagrams
| Comparison | Venus | Earth |
|---|---|---|
| Diameter: | 12,104 km | 12,756 km |
| Mass: | 4.87× 10^24 kg | 5.97 × 10^24 kg |
| Moons: | 0 | 1 |
| Distance from Sun: | 108,209,475 km | 149,598,262 km |
| Length of Year: | 225 Earth days | 365.24 days |
| Temperature: | 464°C | 15°C |
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