Astronomy Ch. 7B: The Earth and Terrestrial Planets

You have found that Planet Z should have active tectonics and volcanism and an atmosphere produced by volcanic outgassing. What single factor explains why the planet should have these characteristics?

has a large size for a terrestrial planet.

Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by _____. (Video)

human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere

Although the data show only a correlation between the carbon dioxide concentration and the global average temperature, scientists have other reasons to think that a rise in the carbon dioxide concentration actually causes a rise in the global average temperature. All of the following statements are true. Which statements lend support to the idea that carbon dioxide is a cause of planetary warming?

-Models of the greenhouse effect successfully predict the temperatures of Venus and Mars from their atmospheric carbon dioxide amounts. -We understand the physical mechanism of the greenhouse effect, through which carbon dioxide can increase a planet's temperature. -Models of Earth's climate that include recent increases in the carbon dioxide concentration match observed temperature increases better than those that do not include it.

Go to the screen "Key Evidence of Water," and and select the feature called "Recurring Slope Lineae." Study this feature at each of the four zoom levels offered, and be sure to view the animation called "recurring slope linaea (gif)" that you will see at the third zoom level. Which of the following statements are true?

-The recurring slope lineae appear to grow in spring and summer. -The recurring slope lineae are found among impact craters. -The recurring slope lineae look like narrow dark streaks.

Now go to the screen "Major Geological Features," and explore the main screen with labels on and off and elevation on and off. Then complete the sentences below.

-The tallest mountain on Mars is called Olympus Mons. -The long, deep canyon running along the equator is called Valles Marineris. -Tharsis Bulge is a high-elevation region dotted by tall volcanoes. -The large, roundish, low-elevation region in the southern hemisphere is called Hellas Basin

Start on the home screen of the interactive figure, with "Elevation is off." Then turn elevation on, and compare what you see. You may wish to switch back and forth between elevation on and off a few times. Then select the statements below that are true. Note: Features such as impact craters that are actually round in shape are distorted into oval shapes at mid- to high-latitudes by map projection effects.

-There is a large, roundish region of low-elevation in the southern hemisphere. -Most of the northern hemisphere has much lower elevation than the southern hemisphere. -Several large volcanoes are found near or somewhat north of Mars's equator. -There is a long, deep canyon that strectches along a region close to Mars's equator.

Make a prediction: If the rise in carbon dioxide concentration continues at its current pace, the concentration in the year 2050 will be about _____ parts per million.

460

Using only pencil and paper calculations, Arrhenius concluded that a doubling of the carbon dioxide concentration would raise global temperatures by about _____.

5° C

Since the time Arrhenius made his prediction, the carbon dioxide concentration has risen by about 30% and the global average temperature has risen by about 1°C. Which statement below best describes how scientists should evaluate Arrhenius's prediction?

Although Arrhenius's prediction was not exact, the actual change is similar enough to the predicted change to validate the general idea that a rising carbon dioxide concentration would lead to global warming.

Which of the following is not an expected consequence of the rising carbon dioxide concentration or global warming?

Animal deaths due to carbon dioxide poisoning.

As you found in Part A, early Mars had both core convection and a strong magnetosphere. What is the connection between these two things?

Core convection helps generate a magnetic field, and the magnetic field creates the magnetosphere.

What motivated Arrhenius to calculate how changes in carbon dioxide might affect the climate?

He was seeking to understand the causes of ice ages.

Which describes our understanding of flowing water on Mars?

It was important once, but no longer.

Each of the following statements was either true for Mars in the distant past (early Mars) or is true for Mars today. Sort the statements by dragging each into the correct bin. (video)

Early Mars (more than 3 billion years ago): Strong greenhouse effect. Substantial volcanism and outgassing. Strong magnetosphere. Some craters held lakes of water. Core convection. Mars Today: Surface pressure too low for stable liquid water. Solar wind strips atmospheric gas. Very weak greenhouse effect.

Arrhenius was not particularly alarmed by his discovery at the time. What changed that made later scientists become much more concerned about the climate effects of carbon dioxide?

Emissions of carbon dioxide rose much faster than Arrhenius had anticipated.

In Part A, you found that Earth emits only infrared light. This infrared light can be absorbed by greenhouse gases, such as carbon dioxide and water vapor, in the atmosphere. In fact, all the terrestrial planets emit infrared light from their surfaces. The following images show the four terrestrial planets in our solar system. Rank these planets from left to right based on the total amount of infrared-absorbing greenhouse gases in their atmospheres, from greatest to least.

Greatest Greenhouse Gas Abundance- Least Venus, Earth, Mars, Mercury Venus has a thick atmosphere of carbon dioxide. Earth has greenhouse gases primarily in the form of water vapor, carbon dioxide, and methane. Mars has an atmosphere made mostly of carbon dioxide, but its atmosphere is so thin that it contains less total greenhouse gas than Earth's atmosphere. Mercury has essentially no atmosphere at all.

The following images represent four types (wavelength bands) of light. Rank these from left to right based on the amount of each that is emitted (as thermal radiation) by Earth's surface, from greatest to least. If you think that two (or more) types should be ranked as equal, drag one on top of the other(s) to show this equality.

Greatest amount: infrared Least amount: ultraviolet visible x-ray Earth emits thermal radiation characteristic of its surface temperature, which means it is almost entirely infrared (extending, in principle, down into the radio). For Earth, the surface temperature is too low to emit any visible, ultraviolet, or X-ray light, so those are all ranked equally. (Note: Technically, thermal emission extends over all wavelengths, so even at low temperatures there might be an occasional photon of visible or higher-energy radiation. However, this emission is negligible for Earth, which is why we rank them all equal to zero.)

All the following statements are true. Which two represent the two facts that lead us to expect Earth to be warming up as a result of human activity? Be sure to choose two of the statements below.

Human activity is increasing the concentration of carbon dioxide and other greenhouse gases in the atmosphere. Greenhouse gases make Earth warmer than it would be otherwise.

As discussed in the video, the leading hypothesis for why Mars changed holds that interior cooling led to loss of its magnetosphere, allowing the solar wind to strip atmospheric gas away. How has the MAVEN mission provided evidence for this hypothesis?

It has measured rates of gas loss from the atmosphere today.

What is the importance of the carbon dioxide (CO2) cycle?

It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.

The region around 2b has far fewer craters than the region around 2c. The crater floor at 2a is also flat and smooth, without many smaller craters on it. Why are regions 2a and 2b so smooth?

Lava flows covered craters that once existed in these regions.

All of the following statements are true. Which one explains why Mars has lost so much more interior heat than Earth.

Mars is smaller than Earth.

When were the heat-trapping effects of gases that cause the greenhouse effect first measured by scientists?

More than 150 years ago.

Which of the following Mars surface features provides dramatic evidence that volcanism has played a role in shaping the surface of Mars?

Olympus Mons

Assuming that features you see on Mars are similar to features found on Earth, what would a casual inspection of the interactive photo of Mars lead you to suspect about water on Mars?

Surface water only exists as frozen ice.

Go to the screen in the interactive figure called "Major Geological Features." Which of the following statements about the Tharsis Bulge, often simply called "Tharsis," are true?

Tharsis has several large volcanoes. One end of Valles Marineris is connected to Tharsis. Tharsis has higher elevation than surrounding regions.

Based on the evidence that atmospheric carbon dioxide is a cause of planetary warming, what aspect of the graphs should most concern us?

The carbon dioxide concentration today is significantly higher than at any time in the past 800,000 years and is rapidly rising.

Go to the screen "Mars Mission Landing Sites," and and select Opportunity landing site (2004). Explore all five zoom levels offered, making sure to read the captions at the tops of the screens. Based on the information provided, why was the landing site,called Meridiani Planum, chosen for the Opportunity mission?

The region was already known to have minerals likely to have formed in liquid water.

Notice that the peaks and troughs on the temperature graph occur at the about the same times as peaks and troughs on the carbon dioxide graph. What can we infer from this fact alone?

There is a correlation between the carbon dioxide concentration and the global average temperature.

Which terrestrial world has the most atmospheric gas?

Venus

Listed following are characteristics of the atmospheres of Venus, Earth, and Mars. Match each atmospheric characteristic to the appropriate planet.

Venus: almost no surface winds, sulfuric acid clouds, runaway greenhouse effect Earth: atmosphere composed primarily of nitrogen and ultraviolet-absorbing stratosphere Mars: extremely low density atmosphere, global dust storms

In Part A, you found that Planet Z should not have strong winds and violent storms. What single change to Planet Z's characteristics would cause it to have strong winds and violent storms?

a faster rotation rate

In Part A, you found that Planet Z should not have polar ice caps or liquid water. What single change to Planet Z's characteristics would allow it to have these things?

a greater distance from its star

What do we mean by a runaway greenhouse effect?

a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere

In Part A, you found that Planet Z should not have seasons. What single change to Planet Z's characteristics would cause it to have seasons?

a larger axis tilt

On the graphs shown, you can identify an ice age by looking for __________.

a trough (bottom of a dip) on the temperature graph

A tectonic ridge appears to connect points 3a and 3b, crossing several craters. From its appearance, we can conclude that it must have formed

after the area was cratered.

Scientists have confidence in the predictions of today's best climate models because they __________.

agree well with actual data for recent decades

Introduction. The diagram (Figure 1) shows the size, orbital distance, and rotation rate of a hypothetical planet around another star, which we'll call Planet Z. Assume that Planet Z is a terrestrial planet shaped by the same basic processes that shape the terrestrial planets of our solar system and that it orbits a star of the same type and age as the Sun. Based on Planet Z's size, orbital distance, and rotation rate, which of the following properties is it likely to have?

an atmosphere produced by outgassing active tectonics active volcanoes

Label 1a lies on the rim of a large crater, and 1b lies on the rim of a smaller one. Which crater must have formed first?

crater 1a

Go to the screen in the interactive figure called "Key Evidence of Water," then zoom in on the "Southern Highlands." Which geologic processes are most clearly evident in the southern highlands?

impact cratering and erosion

What key process underlies why Mars changed so much from its early conditions to its conditions today?

interior cooling

Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny?

its size

The following images show the four terrestrial planets in our solar system. Rank the planets from left to right based on the amount by which the greenhouse effect increases their surface temperatures, compared to what their temperatures would be without the greenhouse effect, from largest to smallest increase.

largest increase- smallest increase venus, earth, mars, mercury A stronger greenhouse effect means a greater temperature increase, which is why the rankings here are the same as the rankings for Parts B and C. The differences are quite extreme: Mercury has no greenhouse effect, so its temperature is determined solely by its distance from the Sun and its reflectivity. The greenhouse effect raises the temperature of Mars by about 6°C from what it would be otherwise; it raises Earth's temperature by about 31°C (which means our planet would be frozen over without the greenhouse effect); and it raises Venus's temperature by about 510°C, explaining the extremely high temperature of Venus.

The oxygen in Earth's atmosphere was released by

life

Where is the most CO2 that has outgassed from Earth's volcanoes?

locked up in rocks

Using your answers from Part AC, list the following features in order from oldest to youngest.

oldest- youngest: crater 1a the smooth floor of crater 1b the tectonic ridge from 3a to 3b

What, if anything, do you think we should be doing to alleviate the threat of global warming?

reduce the emissions of greenhouse gases replace fossil fuels with alternative energy sources improve energy efficiency

The following images show the four terrestrial planets in our solar system. Rank the planets from left to right based on the strength of the greenhouse effect occurring at their surfaces, from strongest to weakest.

strongest- weakest venus, earth, mars, mercury The greenhouse effect is caused by greenhouse gases in the atmosphere, so more greenhouse gas means a stronger greenhouse effect. That is why the rankings here are the same as the rankings for Part B.

Which region of Earth has warmed the most in recent decades?

the Arctic

Which of the following does NOT provide evidence that Mars once had abundant liquid water on its surface?

the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell

The average temperature over the past 1000 years has been about 15∘C. From the graphs, you can conclude that Earth's average temperature during the past 800,000 years has __________.

varied between about 7∘C and 19∘C The zero level on the graph represents the 15∘C average temperature over the past millennium, so the peaks near +4 on the graph represent a temperature of about 15∘C+4∘C=19∘C and the troughs near −8 represent 15∘C−8∘C=7∘C.

Which of the following is a strong greenhouse gas?

water vapor