Venus thick clouds reflect sunlight well, so Venus is very bright. When it is visible, Venus is the brightest object in the sky besides the Sun and the Moon. Because the orbit of Venus is inside Earths orbit, Venus always appears close to the Sun. When Venus rises just before the Sun rises, the bright object is called the morning star. When it sets just after the Sun sets, it is the evening star. Of the planets, Venus is most similar to Earth in size and density. Venus is also our nearest neighbor. The planets interior structure is similar to Earths, with a large iron core and a silicate mantle (Figure 1.1). But the resemblance between the two inner planets ends there.

venuss surface

Since spacecraft cannot see through the thick atmosphere, radar is used to map Venus surface. Many features found on the surface are similar to Earth and yet are very different. Figure 1.3 shows a topographical map of Venus produced by the Magellan probe using radar. This false color image of Venus was made from radar data collected by the Magellan probe between 1990 and 1994. What features can you identify? Most of the volcanoes are no longer active, but scientists have found evidence that there is some active volcanism (Figure 1.4). Think about what you know about the geology of Earth and what produces volcanoes. What does the presence of volcanoes suggest about the geology of Venus? What evidence would you look for to find the causes of volcanism on Venus? This image of the Maat Mons volcano with lava beds in the foreground was gen- erated by a computer from radar data. The reddish-orange color is close to what scientists think the color of sunlight would look like on the surface of Venus. Venus also has very few impact craters compared with Mercury and the Moon. What is the significance of this? Earth has fewer impact craters than Mercury and the Moon, too. Is this for the same reason that Venus has fewer impact craters? Its difficult for scientists to figure out the geological history of Venus. The environment is too harsh for a rover to go there. It is even more difficult for students to figure out the geological history of a distant planet based on the information given here. Still, we can piece together a few things. On Earth, volcanism is generated because the planets interior is hot. Much of the volcanic activity is caused by plate tectonic activity. But on Venus, there is no evidence of plate boundaries and volcanic features do not line up the way they do at plate boundaries. Because the density of impact craters can be used to determine how old a planets surface is, the small number of impact craters means that Venus surface is young. Scientists think that there is frequent, planet-wide resurfacing of Venus with volcanism taking place in many locations. The cause is heat that builds up below the surface, which has no escape until finally it destroys the crust and results in volcanoes. Click image to the left or use the URL below. URL:




Venus rotates in a direction opposite the other planets and opposite to the direction it orbits the Sun. This rotation is extremely slow, only one turn every 243 Earth days. This is longer than a year on Venus it takes Venus only 224 days to orbit the Sun. Diagram of Venuss interior, which is simi- lar to Earths.


extreme atmosphere

Venus is covered by a thick layer of clouds, as shown in pictures of Venus taken at ultraviolet wavelengths (Figure This ultraviolet image from the Pioneer Venus Orbiter shows thick layers of clouds in the atmosphere of Venus. Venus clouds are not made of water vapor like Earths clouds. Clouds on Venus are made mostly of carbon dioxide Click image to the left or use the URL below. URL: The atmosphere of Venus is so thick that the atmospheric pressure on the planets surface is 90 times greater than the atmospheric pressure on Earths surface. The dense atmosphere totally obscures the surface of Venus, even from spacecraft orbiting the planet.


instructional diagrams

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earths nearest planetary neighbor and closest in size and density is ____.

a) jupiter

b) pluto

c) uranus

-->  d) none of the above

venus has a core made of __ and a mantle made of _.

-->  a) iron; silicate

b) iron; silicone

c) silver: iron

d) none of the above

clouds on venus are made of

a) water vapor like on earth.

b) acid.

-->  c) carbon dioxide and a bit of sulfur dioxide.

d) methane and ozone.

venus orbits the sun _ than earth and rotates on its axis _.

-->  a) faster; slowly

b) faster; quickly

c) slower; slowly

d) slower; quickly

scientists could learn a lot about the surface of venus through telescopes since the planet is so close.

a) true

-->  b) false

venus has extremely high atmospheric pressure and an intense greenhouse effect.

-->  a) true

b) false

volcanism on venus

a) is due to plate tectonics.

-->  b) occurs when too much heat builds up below the surface.

c) has not occurred for around 4 billion years.

d) all of these.

a topographical map of venus reveals

a) mountains and valleys

b) large plains of lava

c) volcanoes

-->  d) all of the above

scientists know that venus surface

a) is very young.

b) has few impact craters compared with mercury and the moon.

c) shows a lot of recent volcanic activity.

-->  d) all of these.

venus is the 2nd hottest planet in the solar system, after mercury.

a) true

-->  b) false

diagram questions

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