Venus ... Earth's not really sister planet

Introduction to Venus

Venus was long considered to be Earth's twin, a planet whose thick clouds must have harbored lush vegetation and exotic animal life. When the true nature of the clouds was discovered and the term "greenhouse effect" applied to the planet by Dr. Carl Sagan, Venus became more like a hellish place than an Eden. Venus holds the distinction of being the hottest of the planets, with surface tempertures exceeding 740K, and it is the hot everywhere. Students who have trouble imagining this heat can do an experiment. Go home, turn on the oven to "bake." After the oven bell chimes that it is up to the desired temperature, open the oven door and stick your arm in the oven for a while and say, "Wow!, Venus is twice as hot as this oven!" In appearance, Venus looks like a yellow, cloud-covered world, and the only way to see the surface is either by landing there or with radar mapping since the entire planet is always covered by clouds. Venus is tipped upside down, or more accurately, Venus is right-side up but spinning clockwise so that the Sun rises in the west and sets in the east. Additionally, Venus is the only planet whose rotation length exceeds its revolution, meaning that a Venus day is longer than its year. Finally, Venus has so much atmosphere that the pressure at the surface would be 90 times that of Earth, flattening anyone who dared to be there, and besides, the clouds rain battery acid. There is not a worse place to be in the entire solar system with the possible exception of Jupiter's moon Io. AT THE BOTTOM OF THIS PAGE IS A SPECIAL SECTION ABOUT THE UNIQUE NATURE OF THE SURFACE OF THIS PLANET.

Planetary data

Mass (kg), and mass relative to Earth

4.869x1024 kg = .8150 earths

Equatorial diameter (km)

12,100 km

Mean density (gm/cm3)

5.24

Acceleration of gravity (m/s2)

8.869

Velocity of escape (km/s)

10.4

Period of rotation
243.01 days

Period of revolution

224.701 days

Aphelion (AU)

.7282

Aphelion (km)

108,940,000

Perihelion (AU)

.7184

Perihelion (km)

107,470,000

Mean orbital distance from the sun (AU)

.7233

Mean orbital distance from the sun (km)

108,200,000

Orbital velocity (km/s)

35.03

Eccentricity

.0068

Oblateness

0.0

Inclination to the ecliptic

3.394 degrees

Inclination of the equator to the orbit

177.3 degrees

Number of natural satellites

0

Names of natural satellites

 

More Information on the Planet Venus from the Nine Planets Website

Much of the information below is direct from the Nine Planets Website. Some material has been altered by me for this course, while other items and comments are directly copied. I hope to maintain a continuous update of this material to keep up with the findings from space satellites and telescopes.

Venus is the second planet from the Sun and the sixth largest. Venus' orbit is the most nearly circular of that of any planet, with an eccentricity of less than 1%.
orbit: 108,200,000 km (0.72 AU) from Sun
diameter: 12,103.6 km
mass: 4.869x1024 kg


Venus (Greek: Aphrodite; Babylonian: Ishtar) is the goddess of love and beauty. The planet is so named probably because it was the brightest of the planets known to the ancients. (With a few exceptions, the surface features on Venus are named for female figures.) It is the brightest object to appear in the night sky, with only the Sun and Moon being brighter, unless a star nearby happens to go supernova.


Venus has been known since prehistoric times, and due to its brightness in the sky, it has been an object of much study and speculation. Like Mercury, it was popularly thought to be two separate bodies: Eosphorus as the morning star and Hesperus as the evening star, but the Greek astronomers knew better.

 

 

Since Venus is an inferior planet, meaning that it orbits inside the orbit of Earth, andtherefore it shows phases when viewed with a telescope from the perspective of Earth. Galileo's observation of this phenomenon was important evidence in favor of Copernicus's heliocentric theory of the solar system.

The images above and below depict the phases of Venus that astronomers can view through their telescopes, and which Galileo observed such a long time ago. The phases of Venus are due to its interior position relative to Earth's. Of interest is that the crescent phases is significantly larger because during that phase, Venus is closer to the Earth. While the crescent exposes the least amount of sunlit Venus to Earth, it is still the time when Venus will appear most bright to the naked eye in the evening or morning sky.

Spacecraft Visits to Venus

The first spacecraft to visit Venus was Mariner 2 in 1962. It was subsequently visited by many others (more than 20 in all so far), including Pioneer Venus, the Soviet Venera 7 that was the first spacecraft to land on another planet, and Venera 9 that was the first to return photographs of the surface. The Venera 13 images are seen below. During the height of the Cold War, the American and Soviet scientists worked out an informal gentlemen's agreement that was actually followed in spite of the paranoia and spying between the two world superpowers. It was decided that the Soviets would explore Venus and share their findings while the Americans would explore Mars and share those findings. While the Soviets experienced many failed attempts to land craft on Venus, they were successful several times and the images are a real surprise to everyone.

Most recently, the orbiting US spacecraft Magellan produced detailed maps of Venus' surface using radar (left). From the image, it is obvious that Venus has the same type of surface as does the Earth, without the oceans. The blue denotes basaltic lowlands, and the green and yellow areas are continental highlands, sort of like Asia or North America. While Venus lacks any plate tectonic movement, there is still geologic activity with volcanism, but all of the volcanoes are shield domes like Hawaii and Mars.

 

 

 

 

 

Venus Topography

Below is a topographical map of the Venusian surface taken from radar imagry of Magellan. You can click on the map to see a larger version of the image, or click on topo map to get a map with labels. Venus surface.

Venus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrograde (meaning that Venus spins in a clockwise direction such that the Sun would rise in the west and set in the east). In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach. Whether this is a resonance effect or merely a coincidence is not known. I find two interesting points here:

1) Astronomers like order in their study. To them, Venus offers some challenge to this order. All planets spin counter-clockwise except Venus. Instead of simply stating that Venus has almost no tilt and spins clockwise, astronomers have instead chosen to designate Venus as a planet that spins in the "proper" counterclockwise direction, but happens to do so upside-down.

2) Imagine going to school on Venus where a day is 243 days long. You would be in school for 80 straight days, with four classes of 20 days each. Can you sense the joy of math or English for 20 consecutive days? However, you would get a nice lunch break and a long time to sleep :)

Venus is sometimes regarded as Earth's sister planet. In some ways they are very similar:
-- Venus is only slightly smaller than Earth (95% of Earth's diameter, 80% of Earth's mass).
-- Both have few craters indicating relatively young surfaces.
-- Their densities and chemical compositions are similar.
Because of these similarities, it was thought that below its dense clouds Venus might be very Earthlike and might even have life. But, unfortunately, more detailed study of Venus reveals that in many important ways it is radically different from Earth.

The pressure of Venus' atmosphere at the surface is 90 atmospheres (about the same as the pressure at a depth of 1 km in Earth's oceans). I have found this concept of excessive surface pressure hard for my students to grasp, so here is an analogy. On earth, 14.2 pounds of air pressure squeezes down on each square inch of your body. You are totally unaware of this since you were born into this world and adapt to its conditions. On Venus, the pressure is 90 times greater. It is as if you were to go to the weight room of a gym and pick up a few of those large 45 pound circular plates that are put on bars for bench pressing. In fact, you would grab 27 of those plates and pile them on your finger, or your chest, or even your head. This is 1200 pounds of pressure per square inch. You would be quickly flattened. This intensely thick atmosphere is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulfuric acid. This is the same stuff that you might find in your car battery. I recall a time when my battery died, and I needed to trade it in to get a new one. During the drive to the NAPA store, I held the battery on my lap. When I got to the store, the leaking battery juices had eaten large holes in my pants, and I had to ask my friend to take the battery into the store because my pants were ruined. Now imagine having that same kind of acid rain down from the clouds!

Furthermore, these clouds completely obscure our view of the surface. This dense atmosphere produces a run-away greenhouse effect that raises Venus' surface temperature by about 400 degrees to over 740 K (hot enough to melt lead). Venus' surface is actually hotter than Mercury's despite being nearly twice as far from the Sun. What is unusual about the clouds is that their bottoms are about 30 km up from the surface. The greenhouse trapping of solar heat has inflated the atmosphere such that if any rain were to fall, it would evaporate before hitting the ground.

Well, isn't this great? You go outside of your little house on Venus and are immediately flattened by the pressure, spontaneously combust into flames from the excessive surface heat, and hope that acid rain does not scour away whatever is left of you. Actually, the rain would never strike your burnt body because it evaporates and rises back into the clouds well before reaching the surface.

There are strong (350 km/hr) winds at the cloud tops but winds at the surface are very slow, no more than a few kilometers per hour. The Soviets deployed a collection of metal spheres into the upper clouds of Venus. The transmitters in these metal mini-satellites returned information to the Earth and allowed the scientists to measure wind velocity as these metal spheres circled the planet is only 4 days. It took Phineas Fogg 88 days to go around the Earth in his balloon. Imagine his experience in the clouds of Venus!

Venus probably once had large amounts of water like Earth but it all boiled away. You will learn why later on this page. Venus is now quite dry. Earth would have suffered the same fate had it been just a little closer to the Sun. We may learn a lot about Earth by learning why the basically similar Venus turned out so differently.

Why is the atmosphere of Venus (Earth's sister) so different from Earth?


On Earth, CO2 is absorbed in the oceans and rocks. If the absorbed CO2 on Earth were released into the atmosphere, 98% would be CO2 and the atmospheric pressure would be 70x what it is now. So, except for the O2 and water, Earth's atmosphere would be similar to Venus' if the CO2 has not gotten absorbed. The oxygen on Earth is a product of life, the result of photosynthetic splitting of water into O2 and H+ ions that are used to drive the future synthesis of ATP and Glucose.
The water on Venus has disappeared due to the extreme temperatures brought on by the runaway greenhouse effect. The trapped radiant heat from the solar-heated ground caused water vapor to rise to high elevations where is was then broken down into oxygen and hydrogen by ultraviolet radiation (photolysis). The hydrogen, being light, escaped from the gravitational control of Venus. The remaining heavier oxygen radicles combined with other atmospheric gases, and thus water on Venus was lost forever!

Summary of Atmospheric Components

(percentages by volume)

Earth

Venus

CO2

absorbed in rock

free in atmosphere (96.5%)

Nitrogen

free in atmophere (78%)

free in atmosphere (3.5%)

Water

mostly condensed on surface

decomponsed long ago, and hydrogen escaped

Oxygen

free in atmosphere (21%)

no life to produce it


Evolution of Venus' Atmosphere

During secondary atmosphere formation on Venus, the temperature was so high that no oceans formed. (Water is broken down by a process called photolysis, and H2 escapes) and gases are not absorbed back into the rock as they are on Earth. The remaining carbon dioxide gases in the atmosphere (pumped out via volcanism) trapped heat (greenhouse effect). As the temperature rose even more, the planet found itself in a runaway greenhouse effect. The atmospheric heating was unstoppable. Given the closer proximity to the Sun and the extremely slow rotational speed of the planet, Venus was doomed to be lifeless. What early planetary astronomers believed would be a world teeming with life turned out to be a dry, barren, and exceedingly harsh environment, and perhaps the worst surface place in the Solar System to visit.

The variations in concentration from the Earth to Mars and Venus result from the different processes that influenced the development of each atmosphere. While Venus is too warm and Mars is too cold for liquid water the Earth is at just such a distance from the Sun that water was able to form in all three phases, gaseous, liquid and solid. Through condensation the water vapor in our atmosphere was removed over time to form the oceans. Additionally, because carbon dioxide is slightly soluble in water it too was removed slowly from the atmosphere leaving the relatively scarce but unreactive nitrogen to build up to the 78% is holds today.

 

The image to the left depicts what astronomers believe the interior of Venus to be like. It is probably very similar to that of Earth: an iron core about 3000 km in radius, a molten rocky mantle comprising the majority of the planet. Recent results from the Magellan gravity data indicate that Venus' crust is stronger and thicker than had previously been assumed. Like Earth, convection in the mantle produces stress on the surface which is relieved in many relatively small regions instead of being concentrated at plate boundaries as is the case on Earth.

 

 

 

 

 

Venus has no magnetic field, perhaps because of its slow rotation that is insufficient to generate the field from within a molten interior. It has no mechanism to generate the magnetic field and this no mechanism to protect itself from much of the harmful solar energy that Earth's magnetic field protects us from!

 

Surface ... THE GREAT MYSTERY

Most of Venus' surface consists of gently rolling plains with little relief. There are also several broad depressions: Atalanta Planitia, Guinevere Planitia, Lavinia Planitia. There two large highland areas: Ishtar Terra in the northern hemisphere (about the size of Australia) and Aphrodite Terra along the equator (about the size of South America). The interior of Ishtar consists mainly of a high plateau, Lakshmi Planum, which is surrounded by the highest mountains on Venus including the enormous Maxwell Montes.

Data from Magellan's imaging radar shows that much of the surface of Venus is covered by lava flows. There are several large shield volcanoes (similar to Hawaii or Olympus Mons) such as Sif Mons (below right). Recently announced findings indicate that Venus is still volcanically active, but only in a few hot spots; for the most part it has been geologically rather quiet for the past few hundred million years.

sif mons

There are no small craters on Venus. It seems that small meteoroids burn up in Venus' dense atmosphere before reaching the surface. Craters on Venus seem to come in bunches indicating that large meteoroids that do reach the surface usually break up in the atmosphere. The image to the left is of several large craters whose interior is now covered with lava. Following impact, lava welled up from the interior of the planet and smoothed over the crater's interior.

 

 

 

 

 

 

 

 

 

The oldest terrains on Venus seem to be about 800 million years old. Extensive volcanism at that time wiped out the earlier surface including any large craters from early in Venus' history.

Magellan's images show a wide variety of interesting and unique features including pancake volcanoes (left) which seem to be eruptions of very thick lava and coronae (below left) which seem to be collapsed domes over large magma chambers.

 

 

 

 

 

The volcanism of Venus produces mountains identical to the Hawaiian Islands on Earth, and apparently by the same geological process of hotspot venting. While Venus lacks the plate tectonic activity of Earth, there is difficulty explaining the chain of volcanoes seen in the image to the left.

This image is interesting because it deomonstrates the unusual nature of high surface heating on the rock. The 740K temperature does not melt the surface rock, but is does soften it, and thus these mountains have collapsed somewhat into the surface after formation. The result is a "spider-like" appearance.

 

 

 

 

 

 

OK ... SO WHAT IS THE MYSTERY?

On May 4, 1989, a special spacecraft was launched to explore the surface of Venus. Its name was Magellan. While the original satellite was complex and expensive, budget cuts at NASA forced the engineers to cut scientific instruments until all that remained was a powerful radar. As the spacecraft orbited Venus, it sent powerful pulses of energy through the clouds of Venus which would then bounce back to the receiving antenna of Magellan and thus create an "image" of a small area of the surface. Magellan would take a series of such images resulting in a long strip of images that analysts at the JPL called "noodles.: After enough orbits, the noodles were laid side-by-side to create the surface map whose pictures you have been looking at so far.

Two planetary geologists, Robert Strom and Gerald Schaber were looking at the surface images of Venus and were surprised to find that the crater population was random ... literally random. Robert Strom states that he has studied the crater population on all of the solid body planets and moons, and Venus is the ONLY surface with such an unusual distribution of craters. They published in Journal of Geophysical Research 25 August, 1992. The population is seen below, and is from that journal.

venus impace craters

To challenge would-be doubters about the possibility that a natural object could have what seemingly is an unnatural appearance, they generated 50,000 random Monte Carlo point distributions and then presented 5 of those distribution maps along with the Venus crater distribution map, and they challenged the readers to determine which image was Venus and which was a Monte Carlo plot. No one could tell the difference. This clearly meant that the craters on Venus were all distributed in a random manner. The only answer for this crater map would be found in the hypothesis that the entire surface of Venus is the same age. Earth geologists find different parts of the Earth's crust to be widespread across a geologic timeline, from the oldest surface of Australia (4.1 billion years) and Canada (3.9 billion years), to the relatively new surface (any boundary of ocean crust where the plates are separating) which are literally a few thousand years to brand new (such as the eastern edge of the big island of Hawaii). To have a planet whose entire surface is the same age is a confounding riddle, but to have that age be estimated to be 500-800 million years is astounding. Typically, solid bodies in the solar system will exhibit some volcanic activity that alters the surface, or some plate movement that folds the surface. Venus shows signs of volcanism and folding, but none of that avtivity is recent. It is as if there was volcanism and surface crust alteration a long time ago, and both processes just stopped.

Additionally, geologist Robert Grimm was struck by the nature of the crater Cleopatra patera on the topof the extinct volcano Maxwell Montes, seen in the image below..

cleopatra patera

How could such a crater, as well as all of the other craters look pristine? Certainly the surface of Venus was not struck by 3000 large rocks in a massive meteor shower (that completely missed Earth by the way). His conclusion, as well as that of Strom and Schaber was that the entire surface of Venus was the same age, and the estimate of that age is 500-800 million years, and since its early formation, there has been no surface deformation by volcanoes or plate tectonics since. Robert Grimm wonders at the beautifully pristine appearance of all of the Venus craters, and notes that this type of geology is nowhere else in the Solar System. Further adding to the mystery of Venus are the unusual mountains on Venus. When geologists looked at Venusian mountain ranges, they were surprised at the relative steep features. It is well known that the surface of Venus is well over 740K, and under such extreme heat, the mountains would be expected to slump downward and outward. But the mountains on Venus do not exhibit any signs of surface weathering and deformation. Since there was no evidence of any form of plate tectonics like there is on Earth, and since there is no evidence of dormant volcanos slumping under their own weight, geologists who study Earth rocks had no simple explanation for what was seen on Venus. Like the craters, the mountains on Venus have retained their original size, shape, and steepness since very early on! Two questions emerged from these observations. First, how can the entire surface of Venus be the same age and show no signs of recent volcanism or plate deformation as other Solar System bodies do? Second, under the extreme surface temperatures and pressures at the surface of Venus, how do the mountains remain so steep and high?

Dr. Stephen Mackwell designed a very clever experiment to provide a possible explanation for the unusual mountains on Venus. He took two samples of rock that are believed to be similar to those found on Venus. One sample was baked at the high heat of Venus and the other kept at room temperature. He then exerted great pressure in a slowly increasing rate over an every-increasing time and noted that the room temperature rock deformed under the pressure while the bake dry sample retained its original shape. The rock samples that were baked dry were on the order of 10 times more resistant to pressure (10 times stronger) than the unbaked rocks. His conclusion is that the Venus rocks have any potential liquid boiled out of them, become baked dry, and thus are stronger and resistant to slumping or collapse under the downward pressure of gravity or the high heat which would seemingly make the rocks act more like putty. Scientists are quite confident that Venus has a liquid iron-nickle core surrounded by a silicate mantle, overlaid with a silicate lithosphere and thin crust at the surface. Gravitational pressure in the deep interior is responsible for the molten core of Venus. The question for Venus geologists (since "geo" refers to Earth, would rock scientists studying Venus call themselves Venologists?) is then how does the heat from the interior escape? On Earth, the interior hear is carried upward via huge convection cells of non-melted mantle which then pulls thick tectonics plates in various directions, resulting in fresh lava oozing through the cracks. On a slightly smaller scale, volcanoes also release the heatload. But Earth is the ONLY Solar System body that has active plate tectonics. Since there is little or no observed tectonic activity on Venus, the planet must get rid of its internal heat via a different mechanism. Mars (in its past when it had a liquid core), moons like Io, Titan, Enceladus, Tritan, and perhaps even Pluto have significant surface volcanism that can reduce their heatload from the interiors. However, there are no signs of active or even recently active volcanos on Venus. So ... how does Venus get rid of its heat?

Don Turcotte proposed a VERY interesting hypothesis. He poposed that Venus undergoes a planet-wide episode of crustal collapse into the Venus interior, the formation of a planet-wide magma ocean, solidification of that magma, deformation of that new surface from volcanoes and upwelling pressure, and then the process completely stops. The heat from the interior of Venus has thus escaped in one massive moment, the surface cools and lies dormant, and hundreds of years later when the heat from the interior builds up again, the process repeats itself. When he first presented his hypothesis at a meeting, scientists in the audience openly laughed at him! The reason for their derision lies at the fundamental core of Earth geology.

Prior to the mid-1800s, geologists believed in a combination of natural history and divine intervention. Processes on Earth were believed to happen suddenly, as the result of perhaps a massive flood like in the days of the Biblical Noah. Two geologists in particular (Charles Lyell and Thomas Hutton) challenged this thinking and established two great fundamental pillars of geology called Gradualism and Uniformatarianism. Essentially, these two pillars propose that all large-scale geological events on Earth happen a slow and consistent rates over a long period of time. The Grand Canyon was not carved in a matter of weeks by Noah's Flood, but over millions of years as the Colorado River gouged its way through the rocks. Today, all geologists are trained to be Gradualists and Uniformatarianists. Don Turcotte's proposal went against the core of present-day Geology.

Don Turcotte proposed that lithospere of Venus was thick ... perhaps on the order of 300 km. Heat from the interior of Venus would build up, but be unable to escape through the over-lying thick lithosphere and crust. Eventually, the upward pressure of the convecting hot interior rock would cause the entire surface to convulse, get torn apart, and spontaneously sink back into the mantle. This was a pretty simple explanation for the present appearance of the surface of Venus, but such catastrophic events does not fit with the teaching of Gradualism and Uniformitarianism. Dan McKenzie, professor emeritus at Cambridge, and one of the principle pioneers in Earth's Plate Tectonics pushed back against the hypothesis of Turcotte. McKenzie contends that the lithosphere of Venus is thin ... perhaps on the order of 100 km. Internal heat is escaping continuously, and while there is no immediate evidence, the heat loss is vigorous and rapid.

So ... is there any way to resolve the debate? Magellan team members at the JPL came up with a brilliant idea. They proposed re-purposing the Magellan spacecraft. Through a series of thruster firings by Magellan, the spacecraft was brought down to a very low and nearly circular orbital path. Scientists would then measure the very subtle changes in the orbital speed of the spacecraft after it passed over a mountain. The mountain holds more mass, and would give a small gravity boost as the spacecraft passed over, and this small boost would be measurable. The maneuvers to lower Magellan to a new location closer to the surface worked better than expected, and in the words of one engineer, "We got all this beautiful gravity data - pretty much for free."

There is a fantastic video entitled "Venus Unveiled" which chronicles the entire Magellan mission. Here is the direct transcript from those who analyzed the gravity data:

Narration: As it turned out, the gravity data was open to interpretation.

Don Turcotte: I certainly hoped that it would demonstrate that the lithosphere was thick but it really demonstrated it far beyond my wildest expectations.

Dan McKenzie: It seems to me that the data is quite clar and that is nonsense. The lithosphere is thin, not thick.

Stephen Saunders: I think the thermal lithisphere is two or three hundred kilometers thick.

Ellen Stofan: I think it's relatively thin, on the order of a hundred kilometers or less.

Robert Grimm: As much as two hundred kilometers thick.

Don Turcotte: The thickness of the lithosphere on Venus today is close to three hundred kilometers.

Dan McKenzie: It's quite clear from the gravity data that it is not three hundred kilometers thick, that it is no more than a hundred kilometers over the whole planet. The reason why I think Venus is losing heat it because I can see the convestion in the gravity data and it's thermal convection which is very vigorous. It's at least as vigorous as the Earth, and it is bringing up a great deal of heat which is somehow being lost. Now exactly how it's lost we don't know but we can actually see the heat moving.

Don Turcotte: Of course a good geophysicist can model gravity in such a way that he or she can get any answer that they're looking for.

Robert Grimm: I always had this one picture of Venus: a picture of Cleopatra Patea, an impact crater on top of the mountain range Maxwell Montes. Here's this mountain range that's miles and miles high, it's intenselt deformed, it's been broken and crunched up. and yet on top of it is this perfectly pristine, preserved crater. This is a huge problem.

Narrator: It was a problem that the uniformitarians couldn't explain. On an active planet, many of the craters would also be severely deformed - not perfectly preserved.

venuscrater1 venus crater 2 venus crater 3

venus crater 4 venus crater 5

Robert Grimm: I'd been looking at this picture (above row 2 ... far right) for months and months off and on and finally it just wore me down. It just ground me down and ... finally I just had to say look, I was wrong. This business of uniformatarianism just isn't working and I just got to change and to go with what I think is right now and admit it and that is that Venus has undergone a catastrophic change in the last few hundred million years.

Narrator: But the craters have not changed everyone's mind.

Dan McKenzie: At the moment, catastrophism is the only explanation for the craters which works. I don't like catastrophism. I don't know what the answer is. I don't know how to explain that be uniformatarian argument but I haven't given up trying.

I leave the conclusion up to you since the Astronomy and Geology communities are divided on the best answer. But it is really incredible that one set of data can be interpreted so differently, as well as the interesting effect that a set of teaching pillars can potentially jade the objectivity of the reseacher.

 

The Venus Moon?

Venus has no satellites, and thereby hangs a tale of a time when astronomers thought there might be a small moon orbiting the planet.

Even more fascinating is Percival Lowell's sighting of canals (these pages may take a long time to load), a report recently appearing in the October, 2002 Sky and Telescope.

Venus is usually visible with the unaided eye. Sometimes (inaccurately) referred to as the "morning star" or the "evening star", it is by far the brightest "star" in the sky. It is so bright that it is often confused with alien spacecraft. There are several Web sites that show the current position of Venus (and the other planets) in the sky. More detailed and customized charts can be created with a planetarium program such as Starry Night.

The information shown above is from the Nine Planets website, and courtesy of author Bill Arnett. Please go to that site to find any updates I might not have caught.

Here are a few questions I would like you to be able to answer:

1) Give a brief description of the physical appearance of Venus as seen from a telescope.

2) Why is Venus considered Earth's twin?

3) What is it like on the surface of the planet (describe pressure, heat, and rain)?

4) Why should WE concern ourselves with Earth's greenhouse gasses, just because it got bad on Venus?

5) What Russian satellites landed on Venus?

6) What kind of volcanoes are on the surface of Venus?

7) What are the clouds of Venus made of and what is the rain like?

8) What does the Sun do in the Venus sky? Why does it move that way?

9) How fast do the clouds blow high in Venus' atmosphere?

10) What US satellite did the primary mapping of the surface of Venus?

When you think you know the answers to these questions, go to Venus Quiz and send them in to me.

Some connecting links to Venus information are listed below:

Venus from SSE

Venus from JPL

Venus from LANL

You may go back to look at Mercury, or to Earth or move forward toMars. If these choice are worriesome to you, then return to either Inner Rocky World Introduction or the Planet Introduction, or the Syllabus.


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