Venus

By  Fatma Akgül, Pia Krühner, Imke Kraschinski and Jochim Lichtenberger

Hans-Geiger-Gymnasium Kiel, Germany

1. Introduction

As the evening or morning star, Venus is one of the most conspicuous planets. It often shines so brightly in the dark moonlit sky that objects within the path of its light evidence a weak shadow at night. Occasionaly it can also be seen in the daytime: that is if one knows where to look for it. This extensive luminosity can be attributed to several reasons:

• It is often the nearest planet to the Earth.
• It is almost as big as the Earth and approximately twice as big as the two other nearby planets, Mercury and Mars.
• Venus is surrounded by thick clouds, which reflect 76% of the sun’s light.

Due to the large ammount of clouds, the surface of Venus is not visible from the Earth. Therefore, it still wasn’t possible before the 20 th century to make any major discovery about Venus’ surface. Since that time, with the development of the capability of using infrared and radio waves to investigate space, the first data about Venus’ surface has been able to be gathered. But, it wasn’t until 1962, wenn the satellite Mariner flew to Venus that essential, new information about Venus could be sent back to Earth..

Up until the development of radar, it was generally believed that the planet’s rotational period lasted tree or four weeks. Today, however, it is known that one Venus day is 243 Earth days long. One Venus year, the time it takes for Venus to orbit the sun, has 224 days, is somewhat shorter than a Venus day.

2. The Phases of Venus

When Galilei was the first man ever to look at the Venus with a telescope in the year 1610, he made an important discovery. He saw that the venus changed its shape in the course of several months. In the same way as the moon, one time the venus appeared as a circle, one time as a semicircle and then once thin and crescent-shaped. From one full venus to the other is doesn’t take one month as it does for the moon, but 1.5 years.

Galilei explained it like this: In the same way as the moon, the venus is a sphere that reflects the light coming from the sun. From the earth, we can only see the lit part of the venus.

But there was another thing Galilei discovered: The venus sphere has different dimensions. If it is totally seen (same way as the full moon), it appears very small. If it is seen as a thin crescent, it seems that the venus is almost seven times as large as the “full venus”.

The pictures 1 to 8 are photos of the venus, as one can see it from the earth through a telescope. (It is very difficult to make photos of the Venus like these, because Venus is often standing near to the sun in the daylight-sky.

In order to understand the changing shape of the venus, we have built a model (picture).

An electric bulb represents the sun, a table-tennis ball the Venus and a webcam was in the position of the Earth.

We discovered the following:

1. The Venus appears to be large, when it is close to the earth, and small, wehn it is far away. So the planet can’t circle around the earth, as the old greek said.

2. When the Venus appears to be large (when it is close to the Earth), we only see it as a thin crescent; so the sun has to be behind the Venus. When the planet appears to be small, we see it in the whole; so the sun has to shine onto the Venus from our side.

Because of that we have positioned the webcam 40 cm away from the bulb (the sun) and have let the table-tennis ball circle on a circular way with the radius of 28 cm around the bulb. (We have determined the right radius by trying out, so that the venus crescent is (like in the photos) six times larger then the small venus sphere)

Doing this, we have taken these photos.

        

Our photos seem to have the same proportions as the real photos of the venus. In the same way as we did, Galilei came to the conclusion:

The venus circles the sun. Its distance to the sun is 70% of the distance earth-sun.

In order to make clear how the venus phases come into being, we have created a flash-animation.

Animation

3. Venus, the Goddess of Love

Because of its radiant beauty, this planet nearest to the Earth was named after the goddess of love and beauty. In Roman times, Venus was the goddess of springtime and gardens; later she became equated with the Greek goddess Aphrodite. She was especially celebrated as the awarder of victory. She was the wife of the war god Mars. As the mother of Aeneas and the grandmother of Julius, she was the proginitrix of the Emeror Julius’ family (Caesar, Augustus). In 46 BC the largest temple in Rome was erected for her. On the first of April, the ‘Veneralia’ was celebrated to honor Venus. The dove is the symbol of venus. The fifth day of the week Friday (lat. dies veneris, franz. Vendredi) is also named after Venus. As the supposed mother of the founder of Rome Aeneas, Venus is accredited with beeing the protective guardian of the city.

4. Venus- our sister planet

Venus and Earth have many things in comon:

• Venus is only a little bit smaller than the Earth (95% of the Earth’s diameter, 80% of the Earth’s mass).
• Both of them have a few craters; this is an indication of the relatively young surface structure and of the winds and precipitation that have worn away the surface.
• The density and the chemical composition of the solid part of Venus (not the atmosphere) is similar to those of the Earth.
• On the upper of the clouds, the strong winds blow up to 350 km/h; however, on the surface of the planet, the winds are very weak due to the density of the atmosphere. They do not blow more than a few kilometers per hour.
• The major part of Venus’s surface consists of gently curves plains with slightly raised elevations. There are various wide hollows: Atlante Planitia, Guinivere Planitia, Lavinia Planitia. There are two large mountain ranges: Isthar Terra on the northern half of the sphere (approximately as big as Australia) and Aphrodite Terra, wich is along the equator (about as large as South America). The inner region of the Ishtar mountains essentially consists of a high plain, Laksmi Planum, which is surrounded by the highest mountains of Venus. The highest of these are the enormous Maxwell Montes.
• There are only a few craters on Venus. This may perhaps be because small meteorites burn up in Venus’ dense atmosphere before they are able to reach the surface. When there are craters, they occur in clusters. This is an indication that the large meteorites, which are able to reach the surface, normally break up in the atmosphere.
  The oldest landscape on Venus appears to be approximately 800 million years old. At that time, extensive volkanism obliterated the old surface, including the larger craters existing during Venus’ early history.
• The pictures from the Magellan- Mission show a great diversity of interesting and unique characteristics such as pancake volkanoes, which look like pancakes after the eruption of very thick lava and Coronae, the cavities, which may occure above the lava deposits.

5.  The Pionneer Mission to Venus

The americans needes more than 7 years for this mission, in which they concentrated on the investigation of Venus’ atmosphere. They developped equipment to look at the composition of the armosphere, the surface of Venus, and the clouds, winds and temperatures above the planet. Charles F. Hall of NASA’s Arnes- Exploration center was given the task of leading this scientifis undertaking. He has been involved in this program since 1962. In the early 70’s he also supervised the successful launching of Pioneer 6,7,10 and 11 to the planets Jupiter and Saturn.

6. Venus- Not a living space for people

Within the last 25 years, Venus has had to expose many of hid secrets to the ‘eyes’ of numerous, cleverly devised space sondes. Through this reconnaissance, it has become clear that this planet will remain a forbidden land for human beings. If astronauts wanted to land there, their space ships would not only have to withstand an extremely aggressive cloud player of sulfuric acid, but also endure temperatures which are sufficient enough to melt zinc and other metals and withstand pressures which correspond to those experienced at a depth of 800 meters under water. Even if the descent were to succed, the space ship would land in a frighful setting. Beeing flooded by a glowing red beam, the air under the high pressure would change the direction of the radiating light beam, so that it would appear that the landscape entraps the visitors and the boulders would melt away in the air. The lightning storm would be able to dance above the clouds of the distant volkanoes. Even at night, the ground would appear to be slightly glowing because of its temperature.

7. The inside of Venus

Due to the similarities in density, mass and size, it can be assumed that Venus and Earth have the same internal construction. The Earth has a hot, plastic-like mantel and a crust, which is so thin that it is broken up into plates, which shift against one another. Also Venus hat a type of continent, whose area is in ‘gravitational equilibrium’ with the surroundings (isostativ equilibrium). If the extensive relief of Venus is in a state of isostatic equilibrium, thewre must be a large difference in the density of the crust. On Earth, such differences have been produced by various meltings within the Earth’s center. The dense sulfuric acid content of Venus’ atmosphere indicates that such melting processes, which had been connected to the gas eruptions, have also taken place on Venus. There are, however, no indications of an extended tectonic activity upon Venus. By and large, Venus’ crust appears to be thicker than that of Earth’s.

Literature:

David Morrison, Planetenwelten  Heidelberg, Berlin 1999

Lexikon der Astronomie Hg. H. Elsässer Heidelberg, Berlin 1995

Sterne und Weltraum Nr1/ 1993 S 44 (Veus-photos phases)

www.google.de (1. Venus-photo)