What is the leading hypothesis for venuss lack of water

Briefly describe the basic atmospheric characteristics of each of the five terrestrial worlds.

Use the balloon analogy to explain the origin of gas pressure. What is atmospheric pressure, and why does it decrease with altitude? What is 1 bar of pressure?

Is there any atmosphere at the orbital altitude of the Space Station? Explain.

What is the greenhouse effect? Describe how it warms a planet.

What factors determine a world's "no greenhouse" surface temperature? Explain the difference between "no greenhouse" and actual temperatures for each of the terrestrial worlds.

Describe Earth's basic atmospheric structure, from the ground up. How do interactions of sunlight and gases explain the existence of each of the atmospheric layers?

Why is the sky blue? Why are sunrises and sunsets red?

Why does convection occur in the troposphere, leading to active weather, but not in the stratosphere?

What is ozone? How does the absence of ozone on Venus and Mars explain why these planets lack a stratosphere?

What is a magnetosphere? Describe its role in protecting any atmosphere from the solar wind and in creating auroras.

What is the difference between weather and climate?

Describe Earth's global wind patterns and the role of circulation cells. How does rotation affect these cells?

What are clouds made of? How does rain or snow form?

Describe each of the four factors that can lead to long-term climate change.

Describe each process by which atmospheres gain or lose gas. What factors control thermal escape?

Why do the Moon and Mercury have so little atmospheric gas?

How and why do seasons on Mars differ from seasons on Earth?

Describe the leading hypothesis for how Mars lost atmospheric gas. What role does Mars's size play in this process?

What do we mean by a runaway greenhouse effect? Explain why this process occurred on Venus but not on Earth.

Describe four ways in which Earth's atmosphere is unique among the terrestrial worlds, and how each is important to our existence.

What is the carbon dioxide cycle, and why is it so crucial to life on Earth?

Briefly summarize the evidence linking human activity to global warming. What are its potential consequences?

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
If Earth's atmosphere did not contain molecular nitrogen, $\mathrm{x}$ rays from the Sun would reach the surface.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
If the molecular oxygen content of Earth's atmosphere increases, it will cause our planet to warm up.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
Earth's oceans must have formed at a time when no greenhouse effect operated on Earth.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
In the distant past, when Mars had a thicker atmosphere, it also had a stratosphere.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.If Earth rotated faster, hurricanes would be more common

and more severe.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.Mars would still have seasons even if its orbit around the

Sun were perfectly circular rather than elliptical.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
Mars once may have been warmer than it is today, but it could never have been warmer than Earth.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
If the solar wind were much stronger, Mercury might develop a carbon dioxide atmosphere.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
If Earth had as much carbon dioxide in its atmosphere as Venus, our planet would not have oceans.

Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
A planet in another solar system has no life but has an Earth-like atmosphere with plentiful oxygen.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.Which terrestrial world has the most atmosphere? (a) Venus(b) Earth

(c) Mars

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.The greenhouse effect occurs in the (a) troposphere.

(b) stratosphere. (c) lithosphere.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.What kind of light warms the stratosphere? (a) infrared

(b) visible (c) ultraviolet

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.Which of the following is a strong greenhouse gas?

(a) nitrogen (b) water vapor (c) oxygen

In which direction do hurricanes in the Southern Hemisphere rotate?(a) clockwise(b) counterclockwise

(c) either direction

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.What is the leading hypothesis for Venus's lack of water? (a) Venus formed closer to the Sun and accreted very little water.

(b) Its water is locked away in the crust. (c) Its water molecules were broken apart, and hydrogen was lost to space.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.What kind of gas is most affected by thermal escape?(a) greenhouse gases

(b) light gases (c) all gases equally

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.About what fraction of Earth's atmosphere is $\mathrm{CO}_{2}$ ? (a) $90 \%$

(b) $1 \%$ (c) less than $0.1 \%$

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.What causes the release of oxygen into Earth's atmosphere?(a) outgassing(b) vaporization

(c) photosynthesis

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences.
Where is most of the $\mathrm{CO}_{2}$ that has outgassed from Earth's volcanoes? (a) in the atmosphere (b) in space (c) in rocks

Science with Consequences. A small but vocal group of people still dispute that humans are causing global warming. Do some research to find the basis of their claims. Then defend or refute their findings based on your own studies and your understanding of the hallmarks of science discussed in Chapter 3.

Unanswered Questions. Choose one important but unanswered question about Mars's past, and write two or three paragraphs in which you discuss how we might answer this question in the future. Be as specific as possible, focusing on the type of evidence necessary to answer the question and how the evidence could be gathered. What are the benefits of finding answers to this question?

Are We causing Global Warming? Roles: Scribe (takes notes on the group's activities), Advocate (argues in favor of the claim that human activity is causing global warming $),$ Skeptic (points out weaknesses in the arguments made by the Advocate), Moderator (leads group discussion and makes sure everyone contributes). Activity:a. Work together to make a list of scientific observations that have been proposed as evidence that humans are causing global warming. Your list should include, but is not limited to, the evidence in Figures $10.38-10.42 .$ b. Advocate presents the case that humans are causing global warming, drawing on the evidence from part a. c. Skeptic attempts to refute Advocate's case using scientific arguments.

d. After hearing these arguments, Moderator and Scribe decide whose arguments were more persuasive and explain their reasoning. e. Each person in the group writes up a summary of the discussion.

Clouds of Venus. Table 10.2 shows that Venus's surface temperature in the absence of the greenhouse effect is lower than Earth's, even though Venus is closer to the Sun.a. Explain this unexpected result in one or two sentences.

b. Suppose Venus had neither clouds nor greenhouse gases. What do you think would happen to the surface temperature of Venus? Why? c. How are clouds and volcanoes linked on Venus? What change in volcanism might result in the disappearance of clouds? Explain.

Atmospheric Structure. Study Earth's average atmospheric structure (Figure 10.7 ). Sketch a similar curve for each of the following cases, and explain how and why the structure would be different in each case.
a. Suppose Earth had no greenhouse gases. b. Suppose the Sun emitted no ultraviolet light. c. Suppose the Sun had a higher output of X rays.

Magic Mercury. Suppose we could magically give Mercury the same atmosphere as Earth. Assuming this magical intervention happened only once, would Mercury be able to keep its new atmosphere? Explain.

A Swiftly Rotating Venus. Suppose Venus rotated as rapidly as Earth. Briefly explain how and why you would expect it to be different in terms of each of the following: geological processes, atmospheric circulation, magnetic field, and climate history.

Coastal Winds. During the daytime, heat from the Sun tends to make the air temperature warmer over land near the coast than over the water offshore. At night, land cools off faster than the sea, so temperatures tend to be cooler over land. Use these facts to predict the directions in which winds generally blow during the day and at night in coastal regions. Explain your reasoning in a few sentences. (Diagrams might help.)

Sources and Losses. Choose one process by which atmospheres can gain gas and one by which they can lose gas. For each process, write a few sentences that describe it and how it depends on each of the following fundamental planetary properties: size, distance from the Sun, and rotation rate.

Two Paths Diverged. Briefly explain how the different atmospheric properties of Earth and Venus can be explained by the fundamental properties of size and distance from the Sun.

Change in Fundamental Properties. Choose one property of Earth-either size or distance from the Sun-and suppose that it had been different (for example, smaller size or greater distance). Describe how this change would have affected Earth's subsequent atmospheric history and the possibility of life on Earth.

Feedback Processes in the Atmosphere. As the Sun gradually brightens in the future, how can the $\mathrm{CO}_{2}$ cycle respond to reduce the warming effect? Which parts of the cycle will be affected? Is this an example of positive or negative feedback?

Earth to Mars. Section 10.5 discusses what might happen to Earth if it were suddenly moved to the orbit of Venus. What do you think would happen to Earth if it were suddenly moved to the orbital distance of Mars? Write a few sentences explaining your answer.

Global Warming. What, if anything, should we be doing that we are not doing already to alleviate the threat of global warming? Write a one-page editorial summarizing and defending your opinion.

The Mass of an Atmosphere. What is the total mass of Earth's atmosphere? You may use the fact that 1 bar is the pressure exerted by 10,000 kilograms pushing down on a square meter in Earth's gravity. Remember that every square meter of Earth experiences this pressure from the atmosphere above it. Alternatively, you may start with the English unit value for pressure of 14.7 pounds per square inch and convert to kilograms for your final answer. Remember that the surface area of a sphere of radius $r$ is $4 \pi r^{2}$.

The Role of Reflectivity. By assuming $0 \%$ and $100 \%$ reflectivity (respectively), find the maximum and minimum possible "no greenhouse" temperatures for a planet at 1 AU. What reflectivity would be necessary to keep the average temperature exactly at the freezing point? Compare to Earth's actual reflectivity in Table 10.2.

The cooling Clouds of Venus. Table 10.2 shows that Venus's temperature in the absence of the greenhouse effect is lower than Earth's, even though Venus is closer to the Sun. What would Venus's "no greenhouse" temperature be if its clouds were more transparent, giving a reflectivity the same as Earth's? What would the actual surface temperature be in this case if the greenhouse effect increased the surface temperature by the same number of degrees that it does today?

Mars's Elliptical Orbit. Mars's distance from the Sun varies from 1.38 AU to 1.66 AU. How much does this affect its "no greenhouse" surface temperature at different times of year? Comment on how this affects Mars's seasons.

Escape from Venus.a. Calculate the escape velocity from Venus's exosphere, which begins about 200 kilometers above the surface. (Hint:

See Mathematical Insight $4.4 .$. Calculate and compare the thermal speeds of hydrogen and deuterium atoms at the exospheric temperature of $350 \mathrm{K}$. The mass of a hydrogen atom is $1.67 \times 10^{-27}$ kilogram, and the mass of a deuterium atom is about twice the mass of a hydrogen atom. c. In a few sentences, comment on the relevance of these calculations to the question of whether Venus has lost large quantities of water.

Lucky Earth. The climate histories of Venus and Mars make it clear that getting a pleasant climate like that of Earth isn't easy. How does this affect your opinion about whether Earth-like planets might exist around other stars? Explain.

Terraforming Mars. Some people have suggested that we might be able to engineer Mars in a way that would cause its climate to warm and its atmosphere to thicken. This type of planet engineering is called terraforming, because its objective is to make a planet more Earth-like and easier for humans to live on. Discuss possible ways to terraform Mars. Do any of these ideas seem practical? Do they seem like good ideas? Defend your opinions.

Terraforming Venus. Can you think of ways in which it would be possible to terraform Venus? Discuss the possibilities as well as their practicality.

Human Threats to Earth. Write a three- to five-page research report about current understanding and controversy regarding global warming. Be sure to address both the latest knowledge about the issue and proposals for alleviating any dangers associated with it. End your report by making your own recommendations about what, if anything, needs to be done to prevent damage to Earth.

Spacecraft Study of Atmospheres. Learn about a current or planned mission to study the atmosphere of one of the terrestrial worlds (including Earth). Write a one- to twopage essay describing the mission and what we hope to learn from it.

Martian Weather. Find the latest weather report for Mars from spacecraft and other satellites. What season is it in the northern hemisphere? When was the most recent dust storm? What surface temperature was most recently reported from Mars's surface, and at what location? Summarize your findings by writing a 1 -minute script for a television news update on Martian weather.