|
You're welcome, anyone doing mastering astronomy may want to view these... They are questions from chapter 9.
Astronomy Today, 7e (Chaisson/McMillan)
Chapter 9 Venus: Earth's Sister Planet
1) Why is Venus' rotation unusual?
Answer: Venus is the only terrestrial planet to rotate retrograde (or backwards or clockwise) on its axis.
Diff: 1
Section Ref: 9.2
2) Other than it's atmosphere, name two properties of Venus that are unique among the terrestrial planets.
Answer: Venus rotates clockwise and has not been shown to have a magnetic field.
Diff: 2
Section Ref: 9.2
3) What is unusual about the rotational (spin) and orbital periods of Venus?
Answer: Venus' day is actually longer than its year. It takes longer to spin once on its axis than to complete one orbit around the Sun.
Diff: 2
Section Ref: 9.2
4) Why do our best radar maps of Venus came from the Magellan space probe?
Answer: Magellan went into orbit around Venus and used radar to penetrate the clouds and map the surface. Visual wavelength telescopes cannot see through the clouds.
Diff: 2
Section Ref: 9.4
5) What are coronae?
Answer: large, circular volcanic upwells on the surface of Venus
Diff: 3
Section Ref: 9.4
6) Why were the Russian Venera spacecraft so important to our understanding of Venus?
Answer: They were the first spacecraft to soft land on the planet and send images of the surface back to Earth.
Diff: 3
Section Ref: 9.4
7) If Mars' atmosphere is mostly carbon dioxide, why isn't it as hot as Venus?
Answer: Although it has a carbon dioxide atmosphere, Mars' atmosphere is very thin, much less dense than Venus' or even Earth's.
Diff: 1
Section Ref: 9.5
8 ) What is the primary effect the carbon dioxide in Venus' atmosphere has on the planet.
Answer: The high concentration of carbon dioxide has caused a runaway greenhouse effect which results in very high surface temperatures.
Diff: 2
Section Ref: 9.5
9) Why is the atmospheric pressure at the surface of Venus so much higher than Earth's?
Answer: The atmosphere is much more massive than Earth's and extends to a much greater height above the surface.
Diff: 3
Section Ref: 9.5
10) How does the rotation of Venus' clouds compare to the rotation of its surface?
Answer: The clouds rotate much faster than the surface.
Diff: 2
Section Ref: 9.6
9.5 Essay
1) In its orbit about the Sun, when is Venus the brightest as seen from Earth? Why?
Answer: When it is a large crescent, about 36 days before or after inferior conjunction. It is more fully lit when farther away, but also the disk is smaller. The disk is larger closer to inferior conjunction, but less of the sunlit side is facing us.
Diff: 2
Section Ref: 9.1
2) How was the true rotation rate of Venus determined? Why does this make study of the Venusian surface hard for observers on the Earth?
Answer: Radar studies of Venus finally determined that Venus' rotation rate is 243 days, retrograde. Studies of its entire surface from Earth, using radar, is complicated by the fact that almost the same face of Venus appears pointed towards Earth when the two planets are closest
Diff: 2
Section Ref: 9.2
3) What is the suspected reason for the nearly perfect 5:1 resonance between Venus and Earth?
Answer: There is no clear reason for the nearly perfect resonance. Although it is close, the resonance is not perfect, so that it does not actually constitute a resonance. Furthermore the source of the "resonance" would be Earth, but Earth's tidal pull on Venus is not significant enough to cause a resonance. Therefore, there is no reason for the near resonance observed.
Diff: 2
Section Ref: 9.3
4) Discuss the evidence that suggests that Venus is still very active volcanically.
Answer: There are hundreds of volcanoes on the surface of Venus. Atmospheric chemistry has shown levels of sulfur dioxide that show large and frequent fluctuations, which could be produced by active volcanism. Bursts of radio radiation similar to those from volcanic eruptions on Earth have also been observed.
Diff: 2
Section Ref: 9.4
5) Discuss the fate of meteoroids upon entering the atmosphere of Venus. How do the impact craters found on the surface support this idea? How are the numbers of impact craters affected by volcanism?
Answer: All small meteoroids burn up in the thick atmosphere. Only large ones reach the surface. Thus, there are no small impact craters, only large ones. Also, the heavy volcanic activity continuously changes the surface, covering up older impact craters, so that there are few impact craters compared to the Moon or Mercury.
Diff: 3
Section Ref: 9.4
6) Describe how conditions on Venus have produced a runaway Greenhouse Effect.
Answer: Because of Venus' proximity to the Sun, carbon dioxide never got absorbed by surface rocks due to higher temperature. Carbon dioxide is a greenhouse gas and traps heat, so this led to still higher temperature, leading to even more carbon dioxide released from rocks in a vicious cycle. The result is a surface temperature of 730 K.
Diff: 3
Section Ref: 9.5
7) Contrast the compositions and heights of the clouds of Earth and Venus.
Answer: Our weather and clouds of water droplets occur in our troposphere, within about 12 km of the surface. On Venus, the much thicker cloud deck of sulfuric acid droplets lies about 35-50 km above its surface.
Diff: 3
Section Ref: 9.5
8 ) If Venus' clouds block much of the sunlight before it reaches the surface, why is the planet so hot?
Answer: The carbon dioxide in the dense atmosphere creates a greenhouse effect. Some sunlight (and its energy) still reaches the surface and is reradiated as heat. Heat (or infrared radiation) is trapped beneath the atmosphere, causing an increase in the temperature at the surface.
Diff: 3
Section Ref: 9.5
9) The clouds of Earth often generate rain storms on the Earth's surface. Is this true of Venus? Why or why not?
Answer: The sulfuric acid droplets from Venus' clouds are evaporated before they can reach the surface, so the last 20 miles or so down to the surface is surprisingly clear. The Greenhouse effect keeps the surface too hot for any common liquid to exist there, but you might find pools of molten lead in places.
Diff: 3
Section Ref: 9.5
10) Our sister planet does not show plate tectonics on its surface to the degree our Earth does. What are possible explanations?
Answer: Perhaps the high temperature of the Venusian surface prevents the formation of rigid plates like on Earth. Maybe our hydrosphere is a critical lubricant for plate motions. Maybe the crust is thinner, so it is easier for lava to erupt as volcanoes like the coronae and prevent the convective cycle that causes plate movement.
Diff: 3
Section Ref: 9.6
|
Quick Reply
