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Spokane Falls Community College *
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100
Subject
Astronomy
Date
Dec 6, 2023
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57
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MA #4
Due: 11:59pm on Sunday, October 22, 2023
You will receive no credit for items you complete after the assignment is due. Grading Policy
Prelecture Overview: Our Planetary System
First, launch the video below. Then, close the video window and answer the questions at right. You can watch the video again at any point.
Part A
Drag the correct object from the left to the statement that goes with it at the right. Use each choice only once. ANSWER:
Correct
Ranking Task: Orbital Distance, Mass, and Radius of Planets
Part A
The following images show six objects in our solar system. Rank the objects from left to right based on their average distance from the Sun, from farthest to closest. (Not to scale.)
ANSWER:
Reset
Help
Pluto
was studied up close in 2015 by the New Horizons
spacecraft.
Jupiter
has a famous storm known as the Great Red Spot.
Mars
has no surface liquid water today, but shows clear evidence of such water in the distant past.
Uranus
has an axis tilt that gives it very extreme seasons.
Saturn
is orbited by at least two geologically active moons: Titan and Enceladus.
Mercury
has a greater difference in temperature between its day and night sides than any other
world.
The Sun
generates energy deep in its core through the fusion of hydrogen into helium
Eris
is similar in size to Pluto and also considered a dwarf planet.
Neptune
has a large moon, Triton, that almost certainly once orbited the Sun independently.
Venus
has a surface hot enough to melt lead as a result of an extremely strong greenhouse effect.
Earth
has a single moon that is surprisingly large compared to its planet.
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Part B
The following images show six objects in our solar system. Rank these objects from left to right based on their mass, from highest to lowest. (Not to scale.)
ANSWER:
Correct
Be sure to notice that the masses of these objects are vastly different. For example, the Sun is more than 1,000 times as massive as all the planets combined, and Jupiter is more
massive than all the rest of the planets combined.
Part C
The images below show six objects in our solar system. Rank these objects by size (average equatorial radius), from largest to smallest. (Not to scale.)
ANSWER:
Reset
Help
Reset
Help
Closest
Farthest
Lowest mass
Highest mass
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Sizes (radii) do not vary nearly as much as the masses, but the differences are still substantial. For example, the Sun’s radius is more than 100 times that of Earth, while Jupiter’s
radius is more than 10 times that of Earth.
Prelecture Video: Major Features of Our Solar System
Learning Goal:
To recognize the major features of the solar system. Launch the video below, then answer the questions that follow. You can watch the video again at any point. Note that the video is based on the Cosmic Context figure "The Solar System" that
you will find in your textbook. Part A
Which one of the following is not
one of the four major features of the solar system?
ANSWER:
Correct
The precise number of planets is not thought to be of any particular significance, and the division between "planets" and "dwarf planets" is a recent classification scheme that does
not affect the basic ideas in the four major features. That is, for the purposes of the four major features, the dwarf planets are considered to be equivalent to large asteroids or
comets. Part B
Consider the first major feature (orderly motions). Which of the following correctly describe patterns of motion in our solar system?
Select all that apply.
Reset
Help
Planets fall into two major categories (terrestrial and jovian).
Several exceptions to the general trends stand out.
The solar system contains eight planets plus dwarf planets (such as Ceres, Pluto, and Eris).
Large bodies in the solar system have orderly motions.
Swarms of asteroids and comets populate the solar system.
Smallest radius
Largest radius
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ANSWER:
Correct
Be sure to note that while the Sun and most
planets rotate in the same direction that the planets orbit, there are two notable exceptions: Venus and Uranus. Also note that most
major moons orbit in this same direction and in a planet near that of their planet's equator (which means they are not
in polar orbits). Part C
Now consider the second major feature (two types of planets). Which of the following statements are true for the terrestrial and jovian planets in our solar system? Select all that apply.
Hint 1. How to find characteristics of the two types of planets in the Interactive Figure
The Interactive Figure shows the two types of planets, each with a list of significant characteristics. To find these lists, starting from the main screen, first click on Jupiter, Saturn, or
Neptune (but not on Uranus) to bring up the screen titled "Characteristic 2." Now, if you place your cursor on either of the two planets, you will see a list of characteristics appear (in
blue) below the planet.
Hint 2. How can you determine which type of planet is more dense?
Some planets are made mostly of rock and metal, while other planets also contain large amounts of hydrogen. In general, which type of planet has a higher average density, and
why?
ANSWER:
Hint 3. Which planets are terrestrial?
ANSWER:
Hint 4. Which planets are jovian?
The jovian planets are __________.
ANSWER:
ANSWER:
Major moons generally have polar orbits, meaning orbits that take them over the north and south poles of the planet they orbit. All the planets orbit the Sun in nearly the same plane.
The outer planets are so large that they nearly collide with each other on each orbit.
The Sun and most of the planets rotate in the same direction that the planets orbit.
Planets have nearly circular orbits. Inner planets orbit the Sun in the opposite direction from the outer planets.
Planets that contain a lot of hydrogen have a higher density, because hydrogen is the most common element in the universe.
Planets made of rock and metal have a higher density, because gravity pulls harder on rock and metal than it does on hydrogen.
Planets made of rock and metal have a higher density, because under similar temperature and pressure conditions, any volume of rock or metal will have a greater mass
than the same volume of hydrogen.
The terrestrial planets are .
Mercury, Venus, Earth, and Mars
Earth, Mars, Uranus, and Neptune
Jupiter, Saturn, Uranus, and Neptune
Jupiter, Saturn, Uranus, Neptune, and Pluto
Mercury, Venus, Earth, and Mars
Jupiter, Saturn, Uranus, and Neptune
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Note that the characteristics relating to size, mass, and composition are considered to be defining characteristics for the terrestrial and jovian categories; that is, we would identifiy
planets in other systems as terrestrial or jovian if they have these same general characteristics. In contrast, while all the jovian planets in our solar system orbit much farther from
the Sun than the terrestrial planets, there are other solar systems in which jovian planets have been found to orbit much closer to their stars. Part D
The solar system contains vast numbers of small bodies, which we call asteroids when they are rocky and comets when they are icy. These small bodies are concentrated in the region(s) of
the solar system that we call __________.
Select all that apply.
Hint 1. What is the solar corona?
The solar corona is __________.
ANSWER:
Hint 2. Why is Doppler famous?
You've probably heard the last name of a man named Christian Doppler because he discovered __________.
ANSWER:
ANSWER:
Correct
Most asteroids are found in the asteroid belt
between Mars and Jupiter. Comets are concentrated in two regions: the Kuiper belt
just beyond the orbit of Neptune and the much
more distant and roughly spherical region known as the Oort cloud
.
Part E
All the following statements are true. Which of them are considered to be "exceptions" to the general trends described by the first three major features of the solar system?
Check all that apply.
Hint 1. Is Pluto's location surprising?
Notice that Pluto is located in the region of the solar system occupied by the Kuiper belt. Is this surprising?
ANSWER:
Jovian planets have more moons than terrestrial planets.
Jovian planets orbit farther from the Sun than terrestrial planets.
Jovian planets are larger in mass than terrestrial planets.
Jovian planets are larger in size than terrestrial planets.
Jovian planets are made most of metal, rock, and helium.
a belt of asteroids that orbit the Sun
a large spherical region around our solar system that contains many comets
hot gas located above the Sun's visible surface
a belt of comets encircling the Sun
that the frequency of waves coming from an object depends on the object's motion
a belt of asteroids encircling the Sun
the solar corona
the comet belt
the Doppler belt
the Oort cloud
the asteroid belt
the Kuiper belt
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Hint 2. Where does the Sun rise on Venus?
If you were standing on Venus, you would see the Sun __________.
ANSWER:
ANSWER:
Correct
Note that these exceptions must still be accounted for by any reasonable theory of solar system formation. Part F
In the context of studying major bodies of our solar system, what category of object does our Moon best fit?
ANSWER:
Correct
We consider the Moon to be one of the terrestrial worlds because of its similarity in size, mass, and composition to the other terrestrial worlds (Mercury, Venus, Earth, and Mars).
As you will see when we study comparative planetology, this categorization is useful for understanding geological processes on the terrestrial worlds. Ranking Task: Planet Temperature, Orbital Period, and Number of Moons
Part A
The following images show five planets in our solar system. Rank these planets from left to right based on their average surface (or cloud-top) temperature, from highest to lowest. (Not to
scale.)
Hint 1. What factors determine a planet’s average surface temperature?
Which of the following factors determine a planet’s average surface temperature?
ANSWER:
Yes, because other objects in the Kuiper belt are hydrogen-rich, like the jovian planets.
No, because Pluto's ice-rich composition is similar to that of the many comets found in the Kuiper belt.
Yes, because Pluto also has moons that orbit it.
rise in the east and set in the west
remain stationary in the sky at all times
rise in the west and set in the east
Jupiter's largest moon, Ganymede, is even larger than Earth's moon.
Pluto is in the outer solar system but is ice-rich in composition.
Uranus rotates with an axis tilt that lies nearly in the ecliptic plane.
Our Moon has a diameter more than 1/4 the diameter of Earth.
Venus rotates in a direction opposite to the rotation of the other terrestrial planets.
jovian planet
small asteroid
large comet
jovian moon
terrestrial world
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ANSWER:
Correct
Notice that, for these five planets, temperature correlates with distance from the Sun: the closer to the Sun, the hotter the planet. Remember, however, that this is not always the
case, because a planet’s temperature also depends on its reflectivity and on the strength of its greenhouse effect (if any). For example, the greenhouse effect gives Venus a higher
average temperature than Mercury, even though Venus is nearly twice as far from the Sun.
Part B
The following images show five planets in our solar system. Rank these planets from left to right based on the amount of time it takes them to orbit the Sun, from longest to shortest. (Not to
scale.)
Hint 1. What factors determine how long it takes a planet to orbit the Sun?
Which of the following factors determine how long it takes a planet to orbit the Sun?
ANSWER:
ANSWER:
distance from the Sun only
distance from the Sun and reflectivity only
distance from the Sun, reflectivity, and strength of greenhouse effect
distance from the Sun, reflectivity, strength of greenhouse effect, and mass
Reset
Help
distance from the Sun only
distance from the Sun and orbital eccentricity
distance from the Sun, orbital eccentricity, and mass
distance from the Sun, orbital eccentricity, mass, and rotation rate
Lowest temperature
Highest temperature
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Recall that the time it takes a planet to orbit the Sun is called its orbital period
, and that Kepler’s third law tells us that orbital period increases with distance from the Sun. That is
why the ranking order for orbital period is the same as the ranking order for distance from the Sun.
Part C
The following images show four planets in our solar system. Rank these planets from left to right based on the number of moons that orbit them, from highest to lowest. (Not to scale.)
ANSWER:
Correct
Jupiter has many moons as a consequence of its formation, in which moons formed in a disk of material surrounding it and its extended atmosphere at the time allowed it to
capture numerous small bodies into orbit. Mars has two very small moons that it presumably captured at a time when it, too, had an extended atmosphere. Earth’s single but
surprisingly large moon is thought to have formed as a result of a giant impact. Mercury (and Venus) have no moons.
Process of Science: What Should a Theory of Solar System Formation Explain?
Learning Goal:
To understand why, in science, we do not simply attribute major features of the solar system to coincidence. First, launch the video below, which is based on the Cosmic Context figure "The Solar System" that you will find in your textbook, then answer the questions that follow. You can watch the video
again at any point. Reset
Help
Reset
Help
Shortest time
Longest time
Lowest number
Highest number
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Part A
For the purposes of seeking a theory to explain the formation of the solar system, we identify four major features of our solar system. Which of the following represent these four major
features?
Select four statements to represent the four features. ANSWER:
Correct
In the rest of this tutorial, we will explore why these features are important to developing a theory of how our solar system formed. Part B
Consider only the first major feature, which concerns observed patterns of motion in the solar system. Scientifically, which of the following possible conclusions is justified from the patterns
of motion alone
?
Hint 1. How to approach the problem
The key to answering this question is to recognize that all of the statements are true but only one of them is directly supported by the observed patterns of motion. Ask yourself, for
example, do the patterns of motion in the solar system
allow us to draw any conclusions about the birth of our galaxy
? Apply similar reasoning as you consider all the answer
choices.
ANSWER:
Correct
Continue to Part C to explore why
this conclusion is justified. Part C
Now consider why
the observed patterns of motion lead to the conclusion that the planets were not born in separate, random events. The reason for this conclusion is that, if
the planets had
been born in separate, random events, we would expect that __________.
ANSWER:
The largest planet, Jupiter, has a mass greater than all the other planets combined. Several exceptions to the general trends stand out.
Large bodies in the solar system have orderly motions.
Planets fall into two major categories (terrestrial and jovian).
The solar system contains eight planets plus dwarf planets (such as Ceres, Pluto, and Eris).
Swarms of asteroids and comets populate the solar system.
The planets started out quite small and grew to their current sizes as they gradually accreted more material.
The planets were not
born within the past million years, but instead they must have been born billions of years ago.
The planets were born from a giant cloud of gas that rotated in the same direction that the Milky Way Galaxy rotates.
The planets were not
each born in a separate, random event.
there would be many different types of planets, rather than just two major types
planets would orbit at much higher speeds than they actually do
none of the planets would have ended up with moons
planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane
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In science, we form hypotheses to explain something, then use the hypotheses to make predictions that we can test. In this case, we have two alternate hypotheses: random
births or birth from a single cloud of gas. The hypothesis of random births predicts random orbits, which does not agree with reality and therefore has been discarded. The
hypothesis of birth from a single cloud predicts patterns of motion that match those we observe; this match of prediction and observation provides evidence in favor of the
hypothesis.
Part D
Today, scientists have a theory (the nebular theory
) that explains all the major characteristics of the solar system. In science, we expect a theory like this not only to explain the observed
characteristics of our solar system but also to predict __________.
ANSWER:
Correct
A scientific theory must always make testable predictions, because that is the only way we can evaluate the validity of the theory. In the case of a solar system theory, it should
successfully explain the general characteristics of other solar systems. Prelecture Overview: Formation of the Solar System
First, launch the video below. Then, close the video window and answer the questions at right. You can watch the video again at any point.
Part A
What are four key features of our solar system that any theory of solar system formation must be able to explain?
Select exactly four responses.
ANSWER:
Correct
As discussed in the video, these four features are all successfully explained by the nebular theory. Part B
We expect a scientific theory to be able to make predictions that can be tested. Which of the following is a prediction of the nebular theory that has been verified by observations?
ANSWER:
some major change that will eventually occur in our own solar system
the exact details of planets and their orbits in all other solar systems
which planets have life
general characteristics of other solar systems
Planets fall into two major categories.
There are vast numbers of asteroids and comets.
The Sun generates energy through fusion of hydrogen into helium.
There are clear patterns to the rotation and orbits of large bodies in the solar system. There are a few notable “exceptions to the rules.”
The solar nebula collapsed due to gravity.
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The nebular theory explains planetary formation as a natural part of the star formation process, and therefore predicts that planets should be fairly common around other stars.
This prediction was made long before we ever discovered such planets, so the fact that planets are indeed common is a tremendous predictive success for the nebular theory. Part C
The "giant impact hypothesis" refers to the idea that ___________.
ANSWER:
Correct
Review the video or your textbook for the details of how scientists suspect our Moon formed in a giant impact. Process of Science — Extraordinary Claims: A Giant Impact Made Our Moon
Learning Goal:
To consider the evidence that leads most scientists to conclude that the Moon was formed in a giant impact.
Introduction.
Read the Extraordinary Claims text around which this tutorial is focused. You may also wish to review sections of your textbook relevant to the claim.
Part A
The statements below are all true. Some of them represent important reasons why the giant impact hypothesis for the Moon’s formation is taken seriously, and some of them are not
relevant to deciding between this and other hypotheses. Sort the statements into the correct bin according to whether or not they provide important support to the giant impact hypothesis.
Hint 1. Figure Illustrating the Giant Impact Hypothesis
The giant impact hypothesis holds that the Moon formed as a result of a giant impact between the young Earth and a Mars-size planetesimal, as illustrating in the figure below.
Hint 2. The Meaning of “Easily Vaporized Ingredients
Large planets should have at least some moons that are larger than the smallest planets. Planetary orbits should lie in approximately the same plane as the disk of the Milky Way Galaxy.
Many stars should have planets.
Earth-size planets should have fairly large moons. dinosaur extinction was caused by the impact of an asteroid. the planets formed when another star nearly collided with our Sun. our Moon formed when a Mars-size object collided with the young Earth. large craters on the Moon were formed by large impacts.
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Easily vaporized ingredients refer to water and other materials that vaporize to become gas at relatively low temperatures — low enough that we would expect these materials to
have vaporized as a result of the heat of a giant impact collision.
ANSWER:
Correct
Note the importance of the combination of modeling and observations. Models help us understand what conditions must have been like in the early solar system, showing that
there must have been a great many leftover planetesimals, some large enough to cause giant impacts. Observations of the Moon’s composition show that it is consistent with
formation in a giant impact, which would have led to have a composition similar to Earth’s mantle (because it formed from material blasted out of Earth’s outer layers) and low in
easily vaporized ingredients (because these ingredients would have remained gaseous and therefore would not have participated in the Moon’s accretion).
Part B
Consider the three items from Part A that are not
relevant to the giant impact hypothesis. As you’ll learn in later chapters, the lack of volcanoes is a result of the Moon’s relatively small size.
But what explains the other two items — the Moon’s synchronous rotation and gradually increasing distance from Earth?
ANSWER:
Correct
As discussed in the section of your textbook on tides, the Moon’s synchronous rotation arose as tidal friction slowed the Moon’s rotation until its period matched its orbital period.
The Moon’s gradually increasing distance is a result of the fact that tidal friction is still gradually slowing Earth’s rotation, and this leads to forces that push the Moon outward in its
orbit so that the total angular momentum of the Earth-Moon system remains conserved.
Part C
As discussed in the Extraordinary Claims box, when the giant impact idea was first proposed, it was generally thought to be so unlikely that it wasn’t seriously considered until decades later,
after the Apollo missions to the Moon. What key piece of scientific understanding was missing that made it seem so unlikely when first proposed?
ANSWER:
Correct
Models of solar system formation were not yet sophisticated enough to have made the idea of giant impacts seem plausible. The likelihood of a giant impact only began to seem
reasonable after we understood that many large, leftover planetesimals would have been roaming the early solar system.
Part D
The verdict at the end of the Extraordinary Claims box says “Likely correct, though may never be possible to prove definitively.” In the context of models, which of the following best explains
this verdict?
Reset
Help
Synchronous rotation is simply a coincidence, and this coincidence in turn causes the Moon to move farther away with time.
Both are results of the Moon’s small size.
The giant impact would have caused the Moon to rotate synchronously, and the outward fling from the impact would explain the increasing distance.
Both are results of tidal interactions between the Moon and Earth.
An understanding of the difficulty of gravitationally capturing a body as large as our Moon.
An understanding of how heavily cratered the Moon’s surface is.
A precise age for the solar system.
An understanding of the number and size of leftover planetesimals in the early solar system.
Models indicate early solar system
had Mars-size leftover planetesimals
Moon's composition is similar to
Earth's mantle
Moon has a low proportion of easily
vaporized ingredients
Moon has synchronous rotation
(keeps same face to Earth)
Moon lacks active volcanoes
Moon's distance is gradually
increasing
Supports giant impact hypothesis
True but not relevant to giant impact hypothesis
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ANSWER:
Correct
Today’s models use computers to make precise predictions based on mathematical formulations of the known laws of nature. When these predictions match reality (such as the
successfully reproducing the major characteristics of the Moon) we have great confidence that they are on the right track, but we can’t completely rule out that some other scenario
would also produce the same result.
Part E
While we may never be able to prove that our Moon really formed in a giant impact, which of the following would give scientists greater confidence that the model is correct? Select all that
apply.
ANSWER:
Correct
In fact, we already have greater confidence for all three reasons. Models of solar system formation suggest that at least a few other giant impacts should have occurred in our
solar system, and we do indeed see other solar system bodies that appear to have been involved in giant impacts (including Uranus and Pluto). Telescopic observations have
revealed some evidence for giant impacts in other young solar systems. And scientists are continually refining models of the giant impact thought to have formed our Moon, and
these models yield testable predictions that, at least so far, have proven valid.
Key Concept: Understanding the Nebular Theory
Learning Goal:
To understand the nebular theory of solar system formation and the evidence that supports it. View the Narrated Figure: The Formation of the Solar System below, then answer the questions at right. You can watch the video again at any point.
Part A
Observations show that interstellar clouds can have almost any shape and, if they are rotating at all, their rotation is not perceptible. However, the nebular theory predicts that a cloud will
rotate rapidly once it shrinks to a relatively small size. What physical law explains why a collapsed cloud will rotate rapidly?
Hint 1. Why does an ice skater’s rotation speed up?
Why does the ice skater spin faster as she pulls in her arms?
ANSWER:
ANSWER:
A model that precisely reproduces major characteristics of the Moon would seem likely correct, but we can’t go back in time to see that it actually happened that way.
No model could ever be good enough to reproduce the major characteristics of the Moon.
Models are not reality, and we can never trust their results to reflect what might happen in the real world (or universe).
Models are very vague, and cannot be used to make mathematically precise predictions.
Observing evidence of recent giant impacts in other solar systems that are currently in the process of formation.
Having the giant impact model endorsed by a dozen Nobel prize winners.
Smashing together two glass marbles in a laboratory and then gluing the remnants together to make marbles that have the same size ratio as the Earth and Moon.
Creating more sophisticated models of the giant impact that correctly predict many detailed characteristics of the Earth and Moon.
Finding evidence that other giant impacts occurred in our solar system, with a total number of impacts consistent with what models of solar system formation lead us to expect.
Pulling in her arms reduces her radius, and keeping her angular momentum constant requires that her rotation speed increase.
Pulling in her arms reduces her radius, making her gravity stronger.
Newton’s third law of motion predicts it.
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The law of conservation of angular momentum holds that the cloud's total angular momentum should stay unchanged as it shrinks in size. Like a spinning ice skater bringing in her
arms, the cloud's rotation speed therefore increases as it shrinks. More technically, recall that angular momentum is proportional to velocity times radius; therefore, as the radius
shrinks, the velocity of rotation must increase in order to keep the product of velocity times radius unchanged. Part B
The nebular theory also predicts that the cloud should heat up as it collapses. What physical law explains why it heats up?
Hint 1. What causes an object to heat up?
An asteroid or comet slamming into a planet releases a tremendous amount of heat. This heat comes from the __________ of the asteroid or comet.
ANSWER:
ANSWER:
Correct
The law of conservation of energy tells us that energy must always be conserved. Because the cloud has much more gravitational potential energy when it is large in size than
when it is small, its gravitational potential energy must be transformed into other forms of energy, such as heat (thermal energy), as it shrinks in size.
Part C
The nebular theory also predicts that the cloud will flatten into a disk as it shrinks in size. Which of the following best explains why the collapsing cloud should form a disk?
Hint 1. Why are planets and stars round?
Planets and stars are usually round (spherical) because __________.
ANSWER:
ANSWER:
Newton’s third law of motion
the law of conservation of angular momentum
the universal law of gravitation
the law of conservation of energy
Kepler’s second law
internal temperature
kinetic energy
mass-energy
the law of conservation of energy
the universal law of gravitation
Kepler’s second law
Newton’s third law of motion
the law of conservation of angular momentum
they are rotating
that is the most natural shape for any object
gravity pulls equally in all directions
As a star forms near the cloud center, its wind blows away material that is not aligned with its equator, thereby leaving an equatorial disk of material.
Gravity pulls more strongly on material along the rotation axis than perpendicular to it, bringing this material downward into a disk. Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole.
All collapsing objects tend to flatten into a disk, regardless of their rotation.
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Particles in the collapsing cloud inevitably collide with one another. These collisions allow particles to exchange angular momentum, but their total angular momentum must be
conserved. Therefore, many collisions result in an averaging out of the angular momentums of individual cloud particles, a process that brings their orbits into approximately the
same plane.
Part D
As you've seen, the nebular theory predicts that a cloud that gives birth to planets should have the shape of a spinning disk. Which observable property of our solar system supports this
prediction?
Hint 1. How to approach this question
All of the listed choices are actual properties of our solar system, but only one is a direct consequence of the fact that our solar system was born in a spinning, disk-shaped cloud. It
may help you to remember that our Moon is thought to have formed in a random, giant impact some time after the planets formed and that planetary rings are aligned in the
equatorial planes of their planets, which are tilted significantly to the ecliptic plane for Saturn, Uranus, and Neptune.
ANSWER:
Correct
The orbits of the planets reflect the rotation pattern of the flat, rotating disk in which they formed.
Part E
The solar system has two types of planets, terrestrial and jovian. According to the nebular theory, why did terrestrial planets form in the inner solar system and jovian planets in the outer
solar system?
Hint 1. What was the first step in the formation of the planets?
The first step in the formation of the planets within the disk of the solar nebula was __________.
ANSWER:
Hint 2. Under what conditions do different materials condense into solid form?
Compared to ices (such as water, ammonia, and methane), particles of metal and rock could solidify in the solar nebula from gas at __________.
ANSWER:
ANSWER:
The orbit of Earth’s Moon lies very close to the ecliptic plane.
The four largest planets all have disk-shaped ring systems around them.
There are two basic types of planets in our solar system: terrestrial and jovian.
All the planets orbit the Sun in the same direction and in nearly the same plane.
condensation of solid particles from the gas
accretion of solid particles into larger planetesimals
separation of materials in the gas according to density
higher concentration
lower temperature
lower concentration
higher temperature
After the planets formed, the Sun’s gravity pulled the dense terrestrial planets inward, leaving only jovian planets in the outer solar system.
All the planets started out large, but the Sun’s heat evaporated so much material that the inner planets ended up much smaller.
Denser particles of rock and metal sank into the inner solar system, leaving only gases in the outer solar system.
Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner
solar system, making terrestrial planets.
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Only metal and rock could condense at the high temperature of the inner solar system, so the inner planets were built by the accretion of metal and rock. Farther out, ices could
also condense, leading to the accretion of ice-rich planetesimals. Some of these grew large enough for their gravity to attract gas from the solar nebula and become jovian planets.
Part F
Based on the nebular theory as it explains our own solar system, which of the following should we expect to be true for other star systems?
Check all that apply.
Hint 1. Did the nebular theory predict the existence of planets around other stars?
Since 1995, astronomers have discovered hundreds of planets around other stars, implying that many other solar systems exist. Which statement correctly describes what this
discovery meant to the nebular theory?
ANSWER:
Hint 2. How to approach this question
Most of the statements claim that other solar systems will share some characteristics of our own solar system. For each of these characteristics, try to answer the following question:
Did our solar system end up with this characteristic for a reason that is explained by the nebular theory, or was it just a coincidence? If there is a reason, then we would expect the
same to be true in other star systems. If it was coincidence, then we would not expect the same to be true.
ANSWER:
Correct
We expect all solar systems to form in similar ways from collapsing gas clouds and therefore to share basic features, such as the planets all orbiting in the same direction and
nearly the same plane. We also expect planets to form similarly through accretion, with planets that form near a star tending to be terrestrial in nature and planets that form farther
away tending to be jovian; however, as you'll learn in later chapters, the details of planetary formation allow for additional types of planets beyond just those two categories. We do
not
expect particulars that are probably coincidental, such as the precise numbers of planets, to be the same in different solar systems.
Ranking Task: Relative Time Line for Formation of the Solar System
Part A
Provided following are stages that occurred during the formation of our solar system. Rank these stages from left to right based on when they occurred, from first to last.
Hint 1. How do planetesimals form?
True or False? As the solar nebula collapsed, enormous planetesimals formed from the in-falling matter, then slowly broke into smaller objects that became planets.
ANSWER:
Hint 2. What is the solar nebula?
ANSWER:
The discovery came as a complete surprise because the nebular theory implies that our solar system should be unique in having planets.
The discovery lends support to nebular theory because this theory predicts that other stars and planets should form much as they did in our solar system.
The discovery was not relevant to the nebular theory because this theory applies only to our own solar system
Planetary systems should generally have all planets orbiting in nearly the same plane.
Some planetary systems will have terrestrial planets that orbit their star in a direction opposite to the orbital direction of the jovian planets.
Many extrasolar planets should fall into the terrestrial or jovian categories.
Planetary systems will always have four terrestrial planets and four jovian planets.
Jovian planets always form farther from their star than terrestrial planets.
Planetary systems should be common.
True
False
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ANSWER:
Correct
Once the solar wind helped clear away the remaining gas in the solar nebula, the era of planet formation was essentially over. Remember that all these stages occurred over a
period of millions of years, ending about 4 1/2 billion years ago.
Sorting Task: Formation of Terrestrial and Jovian Planets
Part A
Each of the following statements applies either to the formation of terrestrial planets or of jovian planets (but not both), based on our current theory of solar system formation. Drag the
statements into the appropriate bin.
Hint 1. List of terrestrial planets
The terrestrial planets are Mercury, Venus, Earth, and Mars. They are the planets of the inner solar system, made mostly of metal and rock.
Hint 2. List of jovian planets
The jovian planets are Jupiter, Saturn, Uranus, and Neptune. They are the planets found in the outer solar system, made mostly of hydrogen, helium, and hydrogen compounds,
along with metal and rock.
Hint 3. Did orbital speeds vary in the solar nebula?
ANSWER:
ANSWER:
The solar nebula is __________. another name for the Sun
the cloud of gas and dust that gave birth to our solar system
a star-forming cloud located in the constellation Orion
Reset
Help
Orbital speeds in the solar nebula __________. were everywhere the same
obeyed Kepler’s third law and hence were faster in the inner regions and slower at greater distances
were faster at greater distances
large cloud of gas and dust
contraction of solar nebula
condensation of
solid particles
accretion of planetesimals
clearing the solar nebula
Last stage
First stage
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Visual Activity: Condensed Materials in Different Regions of the Disk of the Forming Solar System
Click here to launch the video below on how and where various materials condense in different regions of the disk of the forming solar system, then answer the questions that follow to the right.
Part A
What substances were found in the innermost regions (within about the inner 0.3 ) of the solar system before planets began to form?
Hint 1. What forms (if any) of rock existed within the iinnermost regions (within about the inner 0.3 ) of the solar nebula?
ANSWER:
ANSWER:
Reset
Help
Within 0.3 of the young Sun, rocky material __________. was present as solid flakes
was present as a mix of solid flakes and liquid droplets
was present in gaseous form
was not found in this region
nothing at all
only rocks and metals
only hydrogen compounds
only hydrogen and helium gases
rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form
accreted from
planetesimals of
rock and metal
surfaces dramatically
altered during the
heavy bombardment
large moons formed
in surrounding
disks of material
formed in a region of
the solar system with
lower orbital speeds
formed in regions cold
enough for water to freeze
ejected icy planetesimals
that are now Oort
cloud comets
accreted from
icy planetesimals
Terrestrial Planets
Jovian Planets
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As described in the video and your textbook, all the materials of the solar nebula were present in the inner region, but it was too hot for any of them to condense. As a result, they
were all in gaseous form.
Part B
What substances existed as solid flakes within the innermost regions (within about the inner 0.3 ) of the solar system before planets began to form?
Hint 1. What is the rock/metal condensation line?
What we might call the "rock/metal condensation line" would mark the innermost boundary where __________.
ANSWER:
ANSWER:
Correct
Although all the materials were present in gaseous form, the innermost regions (within about the inner 0.3 ) of the newly forming solar system was too warm for even rocks or
metals to condense into solid flakes.
Part C
Where would you expect terrestrial planets to form in the solar nebula?
Hint 1. What requirement must be met for the formation of terrestrial planets?
ANSWER:
Hint 2. What is the “frost line”?
ANSWER:
ANSWER:
rock or metal could condense into solid flakes
rock or metal could be found in the newly forming solar system
rock or metal was more abundant than hydrogen and helium gases
none
only rocks and metals
only hydrogen compounds
only hydrogen and helium gases
For terrestrial planets to form __________. rocks and metals only need to be present in some form, whether gaseous or solid
atoms or molecules of rock and metal must outnumber all other atoms and molecules
rocks and metals must be present as solid flakes
Beyond the frost line, planetesimals were made __________. only of ice
only of rock and metal
mostly of ice, but mixed with rock and metal
within the innermost regions (within about the inner 0.3 )
anywhere between the innermost regions (within about the inner 0.3 ) and the frost line
anywhere outside the innermost regions (within about the inner 0.3 )
anywhere outside the frost line
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Terrestrial planets are made mostly of metal and rock and therefore formed in the region in which it was cool enough for metal and rock to condense but still too warm for hydrogen
compounds to condense into ices. This means the region between the innermost regions (within about the inner 0.3 ) and the frost line.
Part D
The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________.
ANSWER:
Correct
Because ices could condense only beyond the frost line, we expect jovian planets to form only beyond the frost line. Note that many extrasolar planets appear to be jovian but are
located close to their stars, leading scientists to suspect that these planets migrated inward after originally forming beyond the frost lines of their star systems.
Prelecture Narrated Figure: Radiometric Dating
First, launch the video below. Then, close the video window and answer the questions at right. You can watch the video again at any point.
Part A
What do we mean when we say that a nucleus undergoes radioactive decay?
ANSWER:
Correct
Radioactive decay can happen in many different ways, but in all cases involves a change in the number of protons or the number of neutrons, or both, in the nucleus.
Part B
Suppose you have a rock that, when it solidifies, contains 1 microgram of a radioactive isotope. How much of this isotope remains after five half-lives?
ANSWER:
only rocks and metals
only ices
rocks, metals, and ices
rocks, metals, ices, and hydrogen and helium gases
The mass of the nucleus is converted into high-energy X rays and gamma rays.
The nucleus splits into two equal size pieces.
The nucleus emits radio waves.
The number of protons or neutrons (or both) in the nucleus changes.
1/32 microgram
1/16 microgram
none
1/8 microgram
Cannot be determined without knowing the daughter isotope.
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The video showed you that 1/16 of the parent isotope remains after 4 half lives. So after a fifth half life, half of that 1/16 will remain, which is 1/32. Since the rock started with 1
microgram of the parent isotope, 1/32 microgram remains after 5 half lives.
Consider the graph in for the decay of uranium-235 into lead-207. Use what you learned from the video to answer
the remaining questions.
Part C
Approximately what is the half-life of uranium-235?
ANSWER:
Correct
The answer is found simply by looking at the point on the graph where half of the uranium-235 has decayed into lead-207. This point, which is labeled “1 half-life,” is found at a
position corresponding to about 0.7 on the horizontal axis, which means 0.7 billion, or 700 million, years.
Part D
Suppose you find a rock and measure that 12.5% of the original uranium-235 still remains it, while the other 87.5% has decayed into lead-207. About how old is the rock?
ANSWER:
Correct
Note that 12.5%, which is the same as 0.125 or 1/8, is the amount of parent isotope remaining after three half-lives – a fact you can both see in the video and read directly from
the graph. Therefore the rock is 3 half-lives old. In this case, because the half-life of uranium-235 is about 700 million years (as you found in Part C), the rock is about 3 × 700
million = 2.1 billion years old. (You can also read the age directly from the graph.)
Vocabulary in Context: Solar System Formation
Part A
Match the words in the left-hand column to the appropriate blanks in the sentences in the right-hand column. Use each word only once.
Hint 1. What the solar nebula is
The solar nebula is the piece of interstellar cloud from which our own solar system formed.
Hint 2. What a planetesimal is
A planetesimal is a building block of a planet, formed by accretion in the solar nebula.
1.25 billion years
2.8 billion years
0.5 billion years
700 million years
1.25 billion years
4.5 billion years
2.1 billion years
2.8 billion years
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Hint 3. What the heavy bombardment was
The heavy bombardment was the period in the first few hundred million years after the solar system formed, during which the tail end of planetary accretion created most of the
craters found on ancient planetary surfaces.
Hint 4. What accretion is
Accretion is the process by which small objects gather together to make larger objects.
Hint 5. What the solar wind is
The solar wind is a stream of charged particles streaming outward from the Sun.
Hint 6. What condensation is
Condensation is the formation of solid or liquid particles from a gas.
Hint 7. What the frost line is
The frost line is the boundary in the solar nebula beyond which ices could condense; only metals and rocks could condense within the frost line.
Hint 8. What radiometric dating is
Radiometric dating is the process by which we determine an object’s age through analysis of the abundance of radioactive parent isotopes and their daughter isotopes.
ANSWER:
Correct
Sorting Task: Geological Processes
Part A
Listed below are geographic features of the terrestrial worlds. In each case, identify the geological process: impact cratering, volcanism, erosion, or tectonics (where tectonics is any large-
scale processes affecting the structure of the planetary crust), most
responsible for the feature described. Match the geographic feature to the appropriate geologic process.
Hint 1. Are tall volcanoes required for volcanism?
ANSWER:
Hint 2. How can you distinguish impact craters from volcanic craters?
Reset
Help
1. Our solar system was created by the gravitational collapse of the solar nebula
.
2. Our Moon was most likely formed by a collision between Earth and a Mars-sized planetesimal
.
3. The first few hundred million years of the solar system's history were the time of the
heavy bombardment
, during which Earth suffered many large impacts.
4. Mars was formed by the accretion
of smaller objects.
5. The era of planet formation ended when the remaining hydrogen and helium gas of the solar nebula
was swept into interstellar space by the solar wind
.
6. Ice can form from a gas through the process of condensation
.
7. Hydrogen compounds in the solar system can condense into ices only beyond the frost line
.
8. Radiometric dating
allows us to determine the age of a solid rock.
Volcanism refers to only the building of tall volcanoes.
the building of tall volcanoes and any subsequent lava flows that come from them.
any flow of molten lava across a surface.
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Which of the following would tell you that craters you are observing were formed by impacts rather than volcanism?
ANSWER:
Hint 3. What is tectonics?
The geological process that we call tectonics refers to __________.
ANSWER:
Hint 4. What is required for erosion?
Which of the following is necessary for erosion to occur on a planet or moon?
ANSWER:
Hint 5. What is Valles Marineris?
ANSWER:
Hint 6. What is Olympus Mons?
ANSWER:
Hint 7. How did Mercury’s cliffs form?
ANSWER:
Hint 8. What surface features do we see in the lunar highlands?
ANSWER:
The craters are circular.
The craters have smooth bottoms indicating that lava flowed in them.
The craters are not associated with any mountains or lava flows.
any surface disruption, such as stretching or crumpling, caused by stresses within the interior of the world
only surface changes, such as the movement of continents, caused by the motion of plates around the world’s surface
the surface features that we see when a world has been heavily bombarded by impacts
liquid water
an atmosphere
lava flows
both liquid water and an atmosphere
both liquid water and lava flows
Valles Marineris is a giant mountain on Mars.
a system of dried-up rivers on Mars.
a long system of canyons stretching nearly a fifth of the way around Mars, looking much like a set of giant cracks in the surface.
Olympus Mons is a giant mountain on Mars, with a crater at its top.
a huge impact crater on Mars.
a long system of canyons stretching nearly a fifth of the way around Mars, looking much like a set of giant cracks in the surface.
Mercury’s long, tall cliffs are thought to have formed when Mercury was bombarded by impacts.
the entire planet shrank, causing the surface to crumple.
water gushed through canyons and left great walls exposed as cliffs.
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ANSWER:
Correct
Remember that the four processes are interrelated, so although one may be most important to a particular feature, others often also play a role. For example, some erosion has
occurred on the volcanic island of Hawaii, there are impact craters on the slopes of Olympus Mons, and volcanism and tectonics almost always go hand-in-hand.
Prelecture Overview: Planetary Geology
First, launch the video below. Then, close the video window and answer the questions at right. You can watch the video again at any point.
Part A
Which of the following statements about our solar system's terrestrial worlds are true?
ANSWER:
Correct
As stated in the video, all five of our solar systems terrestrial world are made of metal and rock and are nearly the same age (the Moon is slightly younger). All have core-mantle-
crust interior structures, but the depths of their lithospheres vary.
Part B
The existence of a core-mantle-crust interior structure tells us that a world __________.
The major surface features of the lunar highlands are giant volcanoes.
craters.
smooth plateaus that must once have been flooded by lava.
Reset
Help
They all have active volcanoes. They all have surfaces that are heavily cratered today.
Their interiors all have a core, mantle, and crust.
They all have lithospheres that extend almost all the way to their cores. They are all of nearly the same age. They are all made primarily of rock and metal. Big Island of Hawaii
Mars's Olympus Mons
smooth surfaces of
the lunar maria
old surface features
of the lunar highlands
Earth's Grand Canyon
Mercury's many
long, tall cliffs
current locations of
Earth's continents
Mars's Valles Marineris
Volcanism
Impact cratering
Erosion
Tectonics
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ANSWER:
Correct
The interior must have once been molten so that its material could separate by density, wtih denser materials settling toward the core while less dense materials rose up toward
the surface. Part C
How does the amount of heat released in a planet’s interior by radioactive decay change with time?
ANSWER:
Correct
As stated in the video, particular atom of a radioactive element can decay only once, so over time there is less material left to release heat through decay. Part D
As a general rule, smaller planets __________ than larger planets. ANSWER:
Correct
That is why smaller worlds tend to have less geological activity -- because in a solar system that is more than 4 billion years old, these worlds have already cooled substantially. Part E
Earth has a relatively strong magnetic field, but Mars does not. Which of the following probably explains why Mars lacks a strong magnetic field today?
ANSWER:
Correct
As discussed in the video, Mars probably had a much stronger magnetic field in its early history, but its small size has allowed it to cool much more quickly than Earth, and as a
result the core became too cool for convection.
Interactive Figure: The Greenhouse Effect and Global Warming
First, launch the animation below. Explore the interactive figure to help you answer the questions that follow.
once had a molten interior
has a molten interior today
formed initially from metal, around which rock was later added
is undergoing interior convection
It stays constant at all times. It increases with time. It drops off with time. rotate slower
rotate faster
cool more rapidly
have larger cores
have stronger magnetic fields
Its lithosphere is too thick.
It is too far from the Sun.
Its core is too cool for convection. It rotates too slowly.
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Part A
Click on the first tab at the top of the interactive figure (labeled "The Greenhouse Effect"), then explore what happens as you click among the buttons (labeled "none," "low," "medium," and
"high") that adjust the greenhouse gas concentration. Which of the following occur as the greenhouse gas concentration increase? Select all that apply. ANSWER:
Correct
Greenhouse gases absorb (and re-emit) infrared light, so a higher greenhouse gas concentration leads to more infrared scattering and higher average surface temperature.
Part B
Now click the second tab (labeled "Terrestrial Planet Temperatures"), then explore what happens as you click the button that allows you to add or remove greenhouse gases. Which
terrestrial planet would have its surface temperature the most dramatically changed if its greenhouse gases were removed from its atmosphere?
ANSWER:
Correct
The change is by far the largest for Venus, because it has a thick atmosphere consisting primarily of carbon dioxide, a greenhouse gas.
Part C
Click the third tab (labeled "Global Warming"), then explore the graph and the expanded views you will find by clicking the "?" buttons. Which of the following statements are supported by
the data shown?
ANSWER:
more visible light is absorbed in the lower atmosphere
the average surface temperature falls
more visible light reaches the ground
more infrared light is absorbed in the lower atmosphere
more infrared light comes to Earth from the Sun
less visible light reaches the ground
the average surface temperature rises
Earth
Venus
Mercury
Mars
Human activity has caused the carbon dioxide concentration to swing up and down wildly over the past 800,000 years. Earth's global temperature today is higher than it has ever been before. Rises in global average temperature tend to be closely associated with rises in atmospheric carbon dioxide concentration.
Earth's global average temperature has generally risen over the past century. Atmospheric carbon dioxide levels have risen dramatically over the past century.
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Rising carbon dioxide is closely associated with rising temperatures, and both the carbon dioxide concentration and temperature have been rising over the past century, which is
why scientists are so concerned about global warming. Note that today's temperature is not
the highest it has been in the past 800,000 years, though it is getting close to that
level. (But Earth's temperature has been higher in the more distant past.)
Part D
Click the fourth tab (labeled "Computer Models"), then explore how the graph changes as you click among the three buttons to its left. What is the primary message of the full graph (with all
three curves shown)? ANSWER:
Correct
The red curve represents models that include both natural factors and human contributions, and it provides a close match to actual temperature data (the black curve). Key Concept: The Greenhouse Effect
Learning Goal:
To understand the greenhouse effect and the evidence showing that greenhouse gases make planets warmer than they would be otherwise.
Introduction.
The diagramillustrates the basic mechanism of the greenhouse effect. Study the diagram
and the relevant portions of your textbook before answering the following questions.
Part A
The energy that warms Earth's surface comes primarily in the form of __________.
Hint 1. What does the Sun's color tell us about the light it emits?
The Sun is yellowish-white in color, which tells us that __________.
ANSWER:
ANSWER:
Climate models can successfully reproduce the major recent trends in temperature data by considering natural factors alone. Climate models are unable to account for the major recent trend in temperature data. Climate models successfully reproduce the major recent trend in temperature data only if both human and natural factors are included. its thermal emission spectrum peaks in the visible portion of the spectrum
it emits only yellow and green light
its spectrum has strong emission lines in the yellow and white portions of the spectrum
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In the figure, this fact is illustrated by the yellow squiggly line at the far left.
Part B
Earth's temperature remains fairly steady, which means that Earth must return nearly the same amount of energy to space that it receives from the Sun. In what form(s) does Earth return
most of this energy to space?
Check all that apply.
Hint 1. What kind of thermal radiation does Earth emit?
Earth emits thermal radiation characteristic of Earth's global average temperature of about 288 K. At this temperature, Earth emits __________.
ANSWER:
ANSWER:
Correct
The total amount of energy returned to space in these three forms of radiation is nearly equal to the amount of energy that reaches Earth in the form of sunlight, which is why
Earth's average temperature stays fairly steady. (Note: global warming is
occurring, but the change is taking place over time scales of years, which means the incoming and
outgoing energy at any moment are quite closely balanced.)
Part C
Greenhouse gases in the atmosphere, such as carbon dioxide and water vapor, make Earth warmer than it would be otherwise because these gases __________.
Hint 1. How do greenhouse gases absorb and emit light?
Greenhouse gases consist of __________ when they absorb light with certain wavelengths.
ANSWER:
ANSWER:
heat from Earth's interior
visible light from the Sun
heat from the Sun
ultraviolet light from the Sun
infrared light from the Sun
infrared light, but no visible light
mostly visible light
a combination of infrared and visible light
infrared light emitted by the surface and atmosphere
visible light emitted by the surface and atmosphere
ultraviolet light reflected by the surface
visible light reflected by clouds
visible light reflected by the surface
atoms that are ionized
molecules that begin to vibrate or rotate
molecules that emit green visible light
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Although the absorbed infrared light is quickly reemitted, it is reemitted in a random direction. As a result, greenhouse gases tend to slow the escape of infrared light from Earth to
space, so that there is more heat (which means more energy) in the atmosphere than there would be if the infrared light escaped directly to space.
Part D
According to scientists, the naturally occurring greenhouse effect makes Earth about 31
warmer than it would be if there were no greenhouse gases in our atmosphere. How do scientists
"know" what Earth's temperature would be without greenhouse gases?
Hint 1. Where do greenhouse gases come from?
Most of the greenhouse gases in Earth's atmosphere originally came from __________.
ANSWER:
Hint 2. What if Earth were as far from the Sun as Mars?
Suppose that we could magically take Earth and put it at Mars's distance from the Sun. At this new location, Earth's temperature would be __________ it is now.
ANSWER:
Hint 3. What would Earth be like if it had no greenhouse gases?
If Earth had no greenhouse gases, the global average temperature would be 31
colder than it is today. This means that __________.
ANSWER:
ANSWER:
Correct
Aside from the greenhouse effect, the only factors that affect a planet's average temperature are its reflectivity and distance from the Sun. Since both distance and reflectivity have
been measured, the expected temperature can be calculated easily and precisely. (Note that this assumes that the Sun's total emission of energy remains steady; measurements
and theory both indicate that it varies very little over time scales less than a few million years.)
Part E
All of the following statements are true. Which one provides strong observational support for the claim that greenhouse gases make a planet warmer than it would be otherwise?
Hint 1. Which planet has the greatest amount of greenhouse gases?
absorb visible light coming from the Sun
absorb infrared light emitted by the surface
reflect visible light coming from the Sun
form clouds that emit thermal radiation
human burning of fossil fuels
outgassing by volcanoes
natural decomposition of fossils
significantly colder than
the same as
significantly warmer than
the polar ice caps would be smaller than they are now
the global average temperature would be well below freezing
the global average temperature would be slightly above freezing
They assume that this temperature would be about the same as the temperature of Mars, which has much less of an atmosphere than Earth.
They calculate this temperature from Earth's reflectivity and distance from the Sun.
Ancient fossils allow them to infer Earth's temperature at a time before our atmosphere contained greenhouse gases.
They estimate it by averaging guesses made by many individual scientists.
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In our solar system, the planet with the greatest amount of greenhouse gases is _____.
ANSWER:
ANSWER:
Correct
The fact that Venus is hotter than Mercury despite being nearly twice as far from the Sun tells us that its thick carbon dioxide atmosphere must warm it significantly—just as we
expect from the theory of the greenhouse effect. Part F
Based solely on an understanding of the greenhouse effect (as displayed in the figure), which one of the following statements is true?
Hint 1. How to approach the problem
The key to answering this question is to distinguish between statements that follow directly from our understanding of the greenhouse effect and those that can be true only if we
have additional information to consider. The figure shows only the greenhouse effect, so study it carefully to see which statement follows automatically.
ANSWER:
Correct
The evidence discussed in this tutorial makes it clear that greenhouse gases make a planet's surface warmer than it would otherwise be, so we should expect a rise in the
greenhouse gas concentration to make Earth warmer. It is possible that there can be mitigating factors through feedbacks, but the basic link between greenhouse gas
concentration and global warming is very strong.
Prelecture Narrated Figure: Global Warming Evidence
First, launch the video below. Then, close the video window and answer the questions at right. You can watch the video again at any point.
Part A
When were the heat-trapping effects of gases that cause the greenhouse effect first measured by scientists?
ANSWER:
Venus
Mars
Earth
Earth has a higher average temperature than Mars.
Venus has a higher average temperature than Mercury.
Earth is the only planet with an ozone layer in its atmosphere.
Mercury is much hotter than the Moon.
Global warming poses a grave threat to our future.
Humans are causing global warming.
We should expect an increase in the greenhouse gas concentration to lead to global warming.
We do not yet understand the greenhouse effect well enough to make predictions about how it affects our planet.
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Correct
As noted in the video, these measurements were first made by John Tyndall in 1859, and they have been repeated and refined ever since. In other words, concerns about the
greenhouse effect and global warming are not
new.
Part B
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.
Select all that apply.
ANSWER:
Correct
As explained in the video, these two facts lead us to expect Earth to be warming up as we add more greenhouse gas to the atmosphere, and global temperature data verify that
temperatures are indeed rising.
Part C
Scientists have confidence in the predictions of today’s best climate models because they __________.
ANSWER:
Correct
As shown in the video, the models are very successful at reproducing recent temperature data, and this is why we have confidence that the models are on the right track.
Part D
Which region of Earth has warmed the most in recent decades?
ANSWER:
Correct
As shown in the video, Arctic regions have warmed more than any other regions.
Part E
Which of the following is not
an expected consequence of the rising carbon dioxide concentration or global warming?
In the late 1950s.
In the early 1990s.
More than 150 years ago.
In ancient Greek times.
If the polar caps melted, sea level would be much higher than it is today.
Temperatures are generally warmer in summer and cooler in winter.
Greenhouse gases make Earth warmer than it would be otherwise.
Human activity is increasing the concentration of carbon dioxide and other greenhouse gases in the atmosphere.
Venus has a much stronger greenhouse effect than Earth.
Water vapor is a greenhouse gas, but nitrogen and oxygen are not.
are very complex and include many equations of physics
represent the work of a great many dedicated scientists
have been developed over a period of many years
agree well with actual data for recent decades
the mid-Atlantic
the tropics
the Antarctic
all regions have warmed about the same amount
the Arctic
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ANSWER:
Correct
The carbon dioxide level is nowhere near high enough to poison animals directly. All the other consequences are real; review the video or your textbook if you have questions
about the reasons behind any of them.
Visual Activity: Basic Ideas of the Greenhouse Effect
Launch the animation below, which will help you with the questions that follow. Pay particular attention to the first two tabs ("the greenhouse effect" and "terrestrial planet temperatures."
Part A
On a cloudless day, what happens to most of the visible light headed toward Earth?
Hint 1. What path does visible light take through Earth’s atmosphere?
True or False? When passing through Earth’s atmosphere, visible light is mostly unaffected by molecules in the atmosphere and will follow a straight-line path.
ANSWER:
ANSWER:
Correct
Most visible light passes through our atmosphere, and this light heats the surface as it is absorbed.
Part B
What happens to the energy that the ground absorbs in the form of visible sunlight?
ANSWER:
Increasing acidity of the oceans.
Animal deaths due to carbon dioxide poisoning.
An increase in extreme weather events, including severe winter weather.
Melting of polar ice.
Rising sea level.
True
False
It is reflected by Earth’s atmosphere.
It is absorbed and reemitted by gases in Earth’s atmosphere.
It is completely reflected by Earth’s surface.
It reaches Earth’s surface, where some is reflected and some is absorbed.
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Remember that objects emit thermal radiation characteristic of their temperatures. Earth’s surface has a temperature for which its thermal radiation peaks in the infrared. In other
words, Earth absorbs energy from space in the form of visible light, and returns this energy to space in the form of infrared light.
Part C
The greenhouse effect raises Earth’s surface temperature (from what it would be otherwise) because the infrared light radiated by Earth’s surface __________.
Hint 1. What path does infrared light take through Earth’s atmosphere?
True or False? When passing through Earth’s atmosphere, infrared light is mostly unaffected by molecules in the atmosphere.
ANSWER:
ANSWER:
Correct
As shown in the interactive figure and discussed in your textbook, the infrared light ultimately escapes to space, but its absorption and re-emission along the way has the overall
effect of increasing molecular motions that raise the air temperature from what it would be otherwise.
Ranking Task: Understanding the Greenhouse Effect in Planet Atmospheres
Part A
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.
Hint 1. What determines the wavelengths of light emitted by Earth?
Earth emits thermal radiation, which means it has a spectrum that __________.
ANSWER:
ANSWER:
It is returned upward in the form of infrared light.
It is returned upward in the form of visible light.
It makes the ground continually get hotter and hotter.
True
False
travels directly out to space
becomes permanently trapped by greenhouse gases
is absorbed by greenhouse gases, slowing the escape of this energy to space
is continuous with a peak at a wavelength determined solely by Earth’s surface temperature
has a few emission lines scattered about at all different wavelengths
is continuous except for having evenly spaced absorption lines in all parts of the spectrum
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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.)
Part B
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.
Hint 1. What atmospheric composition data for the terrestrial planets is
The following data on atmospheric pressure and composition can help you complete Part B:
• Mercury: surface pressure = 0 bar; atmospheric composition = helium, sodium, oxygen.
• Venus: surface pressure = 90 bars; atmospheric composition = 96% carbon dioxide.
• Earth: surface pressure = 1 bar; atmospheric composition = 77% nitrogen, 21% oxygen, less than 1% carbon dioxide, plus varying water vapor.
• Mars: surface pressure = 0.007 bar; atmospheric composition = 95% carbon dioxide.
ANSWER:
Reset
Help
Reset
Help
Least amount
Greatest amount
Least greenhouse gas abundance
Greatest greenhouse gas abundance
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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.
Part C
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.
ANSWER:
Correct
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.
Part D
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.
ANSWER:
Correct
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.
Reset
Help
Reset
Help
Weakest
Strongest
Smallest increase
Largest increase
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Process of Science: Predicting Planetary Properties
Learning Goal:
To use your understanding of the terrestrial planets in our solar system to predict properties of terrestrial planets in other solar systems.
Introduction.
The diagram 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.
Part A
Based on Planet Z's size, orbital distance, and rotation rate, which of the following properties is it likely to have?
Check all that apply.
Hint 1. How does size affect the characteristics of a terrestrial world?
Large terrestrial worlds __________ than smaller terrestrial worlds.
ANSWER:
Hint 2. How does orbital distance affect the characteristics of a terrestrial world?
Terrestrial worlds that are close to their star tend to have __________ than terrestrial worlds that are farther away.
ANSWER:
Hint 3. How does rotation rate affect the characteristics of a terrestrial world?
Relatively rapid rotation is required for a world to have __________.
ANSWER:
have more erosion
have higher surface temperatures
retain internal heat longer
thicker atmospheres
more erosion
higher surface temperatures
an atmosphere
active volcanoes
strong winds and violent storms
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ANSWER:
Correct
Continue on to explore why the planet has these characteristics.
Part B
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?
Hint 1. How does size affect the characteristics of a terrestrial world?
Large terrestrial worlds __________ than smaller terrestrial worlds.
ANSWER:
Hint 2. How does orbital distance affect the characteristics of a terrestrial world?
Terrestrial worlds that are close to their star tend to have __________ than terrestrial worlds that are farther away.
ANSWER:
Hint 3. How does rotation rate affect the characteristics of a terrestrial world?
Relatively rapid rotation is required for a world to have __________.
ANSWER:
ANSWER:
an atmosphere produced by outgassing
active tectonics
a surface crowded with impact craters
erosion due to liquid water
seasons
polar ice caps
active volcanoes
strong winds and violent storms
have higher surface temperatures
have more erosion
retain internal heat longer
thicker atmospheres
higher surface temperatures
more erosion
active volcanoes
an atmosphere
violent weather and storms
Planet Z has a slow rotation rate.
lacks axis tilt.
has a large size for a terrestrial planet.
closely orbits its star.
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Large size means more internal heat. This internal heat drives active tectonics and volcanism, which is the source of outgassing.
Part C
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?
Hint 1. How does size affect the characteristics of a terrestrial world?
Large terrestrial worlds __________ than smaller terrestrial worlds.
ANSWER:
Hint 2. How does orbital distance affect the characteristics of a terrestrial world?
Terrestrial worlds that are close to their star tend to have __________ than terrestrial worlds that are farther away.
ANSWER:
Hint 3. How does rotation rate affect the characteristics of a terrestrial world?
Relatively rapid rotation is required for a world to have __________.
ANSWER:
ANSWER:
Correct
The planet is too hot for liquid water or ice, so moving it farther from its star would allow it to cool down. If it cooled enough—but not too much—it could have surface liquid water
and ice caps.
Part D
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?
Hint 1. What are the general requirements for strong winds and violent storms?
If a planet has an atmosphere, the most important factor determining the strength of its surface winds is its __________.
ANSWER:
have higher surface temperatures
retain internal heat longer
have more erosion
more erosion
higher surface temperatures
thicker atmospheres
an atmosphere
active volcanoes
violent weather and storms
a larger axis tilt
a greater distance from its star
a smaller size
a larger size
distance from its star
rotation rate
axis tilt
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ANSWER:
Correct
The basic requirements for strong winds and violent storms are an atmosphere and relatively rapid rotation. An atmosphere is necessary to have wind of any type, while rotation is
necessary to create the forces (in particular, the Coriolis force) that tend to drive winds on a planet's surface. Storms will be even stronger if there is also evaporation of surface
water.
Part E
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?
Hint 1. What causes seasons on Earth?
The most important factor in the existence of seasons on Earth is Earth's __________.
ANSWER:
ANSWER:
Correct
Seasons are caused primarily by axis tilt, so a planet without axis tilt is not expected to have seasons (unless it has a highly elliptical orbit).
Chapter 6 Concept Quiz
Part A - Quiz Question 1
Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is _________.
Hint 1.
Study Figure 6.1 in the textbook and Table 6.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The planets are much more widely separated in the outer solar system than in the inner solar system.
a larger axis tilt
a smaller size
a greater distance from its star
a faster rotation rate
rotation rate
distance from the Sun
axis tilt
a faster rotation rate
a greater distance from its star
a larger axis tilt
a smaller size
about the same
much larger
much smaller
just slightly less
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Part B - Quiz Question 2
How is Einstein's famous equation, E
=
mc
2
, important in understanding the Sun?
Hint 1.
Study the 10-page tour in Section 6.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The "lost" 4 million tons is converted to an amount of energy equal to this mass times the speed of light squared. Note that although 4 million tons per day sounds like a lot, it is
quite small compared to the Sun's total mass.
Part C - Quiz Question 3
In what way is Venus most similar to Earth?
Hint 1.
Study the 10-page tour in Section 6.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This similarity in size means the two planets are probably quite similar in their interior structures and fundamental properties, although they have obvious and important differences
on their surfaces.
Part D - Quiz Question 4
Which planet listed has the most extreme seasons?
Hint 1.
Think about the cause of the seasons and study Section 6.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Remember that seasons are caused primarily by axis tilt. Uranus essentially rotates on its side compared to its orbit, giving it extreme seasons.
Part E - Quiz Question 5
Which of the following is not
a major pattern of motion in the solar system?
Hint 1.
The Sun generates energy to shine by losing 4 million tons of mass each second
The Sun's surface temperature is about 6,000° Celsius
The Sun has a magnetic field strong enough to influence the atmospheres of the planets
the Sun is extremely massive
Both planets are nearly the same size.
Both planets have warm days and cool nights.
Both planets have similar surface geology.
Both planets have similar atmospheres.
Mars
Earth
Uranus
Jupiter
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Study Section 6.2 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This statement is untrue because comets of the Oort cloud, which are the most numerous of all comets, have randomly oriented orbits going in all directions around the Sun.
Part F - Quiz Question 6
Which of the following is not
a major difference between the terrestrial and jovian planets in our solar system?
Hint 1.
Study Sections 6.1 and 6.2 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Terrestrial planets actually contain very little ice because they are made mostly of metal and rock.
Part G - Quiz Question 7
The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
Hint 1.
Study Section 6.2 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This makes the Moon surprisingly large compared to other planet/moon size differences in our solar system.
Part H - Quiz Question 8
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
All of the planets orbit the Sun in the same direction, that is, counterclockwise as viewed from above Earth's north pole.
Nearly all comets orbit the Sun in same direction and roughly the same plane.
The Sun and most of the planets rotate in the same direction in which the planets orbit the Sun.
Most of the solar system's large moons orbit in their planet's equatorial plane.
Terrestrial planets are higher in average density than jovian planets.
Jovian planets have rings and terrestrial planets do not.
Terrestrial planets contain large quantities of ice and jovian planets do not.
Terrestrial planets orbit much closer to the Sun than jovian planets.
The diameter of Earth's Moon is about 1/4 that of Earth.
Jupiter has a very small axis tilt.
Venus does not have a moon.
Saturn has no solid surface.
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To conserve angular momentum, the cloud particles had to move faster around the cloud center as their distance from the center decreased.
Part I - Quiz Question 9
According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
As it shrank in size, gas particles lost gravitational potential energy. Because energy must be conserved, this energy became thermal energy.
Part J - Quiz Question 10
According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
These collisions tend to change random motions into more orderly ones.
Part K - Quiz Question 11
What is the primary basis on which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Einstein's law E
=
mc
2
The law of universal gravitation
The law of conservation of angular momentum
The law of conservation of energy
The law of conservation of energy
The two laws of thermal radiation
Newton's third law
The law of conservation of angular momentum
It flattened as a natural consequence of collisions between particles in the nebula.
The law of conservation of energy.
The force of gravity pulled the material downward into a flat disk.
It was fairly flat to begin with and retained this flat shape as it collapsed.
The atomic mass numbers of various materials
The temperatures at which various materials will condense from gaseous form to solid form.
The amounts of energy required to ionize various materials
The locations of various materials in the solar nebula
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Condensation determined the materials available in solid form in different regions of the nebula.
Part L - Quiz Question 12
According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not
true?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The planetesimals in the outer solar system were not made only of ice; they also contained rock and metal. Remember, if it's cold enough for ices to condense from hydrogen
compounds, it's certainly cold enough for rock and metal to condense as well.
Part M - Quiz Question 13
Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
In other words, meteorites support our models of how accretion should have occurred.
Part N - Quiz Question 14
According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Water ice could condense from the solar nebula gas only beyond the frost line, which lay beyond the orbit of Mars.
Part O - Quiz Question 15
According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian planets but not around the growing terrestrial planets.
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
Both types of planet begun with planetesimals growing through the process of accretion, but only the jovian planets were able to capture hydrogen and helium gas from the solar
nebula.
The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets formed beyond it.
Their appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.
Their appearance and composition matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals.
Their overall composition is just what we believe the composition of the solar nebula to have been, mostly hydrogen and helium.
Their sizes are just what we'd expect if metal and rock condensed and accreted as our theory suggests.
The water was formed by chemical reactions among the minerals in the Earth's core.
Earth formed at a distance from the Sun at which liquid water happened to be plentiful in the solar nebula.
The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
The water was brought to the forming Earth by planetesimals that accreted near Earth's orbit.
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Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
That is, the formation of large moons around jovian planets was much like a smaller version of the formation of planets around the Sun.
Part P - Quiz Question 16
Which of the following is not
evidence supporting the idea that our Moon formed as a result of a giant impact?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The Pacific Ocean is not an impact crater. Moreover, because the continents are rearranged with time, we can be sure that the giant impact occurred long, long before there was a
Pacific Ocean.
Part Q - Quiz Question 17
Why are terrestrial planets denser than jovian planets?
Hint 1.
Study Section 6.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
It was hotter in the inner regions, so only metal and rock could condense, and these materials are denser than the icy material that condensed farther out in the solar system.
Part R - Quiz Question 18
About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems in the universe probably consisted only
of hydrogen
and helium. Which of the following statements is most likely to have been true about these first-generation star systems?
Hint 1.
Study Sections 6.2 and 6.3 of The Essential Cosmic Perspective
.
ANSWER:
The large moons of the jovian planets originally formed in the inner solar system and these moons then migrated out to join up with the jovian planets.
The many moons of the jovian planets remains one of the unexplained mysteries of the formation of our solar system.
Because of their strong gravity, the jovian planets were able to capture numerous asteroids that happened to be passing nearby, and these became the major moons of the
jovian planets.
As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.
The Pacific Ocean appears to be a large crater, probably the one made by the giant impact.
The Moon's average density suggests it is made of rock much more like that of the Earth's outer layers than that of the Earth as a whole.
Computer simulations show that the Moon could really have formed in this way.
The Moon has a much smaller proportion of easily vaporized materials than Earth.
Gravity compresses terrestrial planets to a higher degree, making them denser.
The terrestrial planets formed in the inner solar nebula, where only dense materials could condense.
The Sun's gravity gathered dense materials into the inner solar system.
Actually, the jovian planets are denser than the terrestrial planets.
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Asteroids are made from metal and rock, and comets are made mostly of frozen hydrogen compounds; all these materials require elements besides hydrogen and helium.
Part S - Quiz Question 19
Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40)
present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?
Hint 1.
Study Section 6.4 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The current 10 micrograms of potassium-40 is 1/8 of the original 80 grams, which means the amount of potassium-40 has declined by a factor of 8. Therefore, three half-lives have
passed (since 2
= 8) and the rock is 3×1.25 = 3.75 billion years old.
Part T - Quiz Question 20
How do scientists determine the age of the solar system?
Hint 1.
Study Section 6.4 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The oldest meteorites are presumed to be material that condensed early in the history of the solar system and therefore represent the time at which the planets began to form.
Chapter 7 Concept Quiz
Part A - Quiz Question 1
The cores of the terrestrial worlds are made mostly of metal because ______.
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
There were no comets or asteroids in these first-generation star systems.
These first-generation star systems typically had several terrestrial planets in addition to jovian planets.
Jovian planets in these first-generation star systems had clouds made of water and other hydrogen compounds.
Like the jovian planets in our solar system, the jovian planets in these first-generation systems were orbited by rings.
2.5 billion years
1.25 billion years
5.0 billion years
3.75 billion years
Radiometric dating of the oldest Earth rocks
Theoretical calculations tell us how long it has taken the planets to evolve to their present forms
Radiometric dating of Moon rocks
Radiometric dating of meteorites
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This sinking was part of the process called differentiation.
Part B - Quiz Question 2
The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that _________.
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
A smaller object has proportionally more surface area through which to lose its interior heat.
Part C - Quiz Question 3
Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The mantle is solid. Mantle convection is the slow flow of this solid rock, but it occurs too slowly to notice on human time scales. (The cycling time for rock from the bottom to the
top of the mantle is about 100 million years.)
Part D - Quiz Question 4
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of
Earth?
Hint 1.
Study Sections 7.1 and 7.3 of The Essential Cosmic Perspective
.
ANSWER:
the core contained lots of radioactive elements that decayed into metals
metals sunk to the centers a long time ago when the interiors were molten throughout
over billions of years, convection gradually brought dense metals downward to the core
the terrestrial worlds as a whole are made mostly of metal
gas bubbles form and rise upward in boiling water
a large baked potato takes longer to cool than a small baked potato
Earth contains more metal than the Moon
thunderstorms tend to form on hot summer days
A rapid, up and down churning of the material in the mantle
Hot molten rock rising upward throughout the mantle and cool, solid rock falling downward
Not much; on human time scales, the mantle looks like solid rock.
Dense metals falling downward while low-density rock rises upward
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Convection of the molten core is required for a global magnetic field.
Part E - Quiz Question 5
What are the two geological features that appear to set Earth apart from other terrestrial worlds in our solar system?
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Neither of these features appears to exist on any other terrestrial world in our solar system.
Part F - Quiz Question 6
Which of the following general statements about Earth's atmosphere is not
true?
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Only greenhouse gases influence surface temperature, and neither oxygen nor nitrogen is a greenhouse gas.
Part G - Quiz Question 7
Which of the following best describes how the greenhouse effect works?
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
Mars's interior has cooled so much its molten core layer no longer undergoes convection.
Mars rotates much slower than the Earth.
Mars is too far from the Sun to have a global magnetic field.
The Martian core is made of rock, while Earth's core is made of metal.
Mantle convection and a thick atmosphere
Plate tectonics and a high level of erosion
Significant volcanism and tectonics
A dense core and plate tectonics
Without the relatively rare gas called ozone, Earth's surface would be bathed in dangerous ultraviolet light from the Sun.
The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.
Gas high in the atmosphere absorbs dangerous X-rays from the Sun.
The oxygen in our atmosphere was released by living organisms.
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This is the basic mechanism of the greenhouse effect, and it explains why more greenhouse gases mean more warming.
Part H - Quiz Question 8
Suppose that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be ________.
Hint 1.
Study Section 7.1 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Without the greenhouse effect, Earth's average temperature would be about –16°C, which is well below freezing (0°C). Thanks to the greenhouse effect, the actual global average
temperature is about 15°C.
Part I - Quiz Question 9
Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria
. What can we conclude?
Hint 1.
Study Section 7.2 of The Essential Cosmic Perspective
.
ANSWER:
Correct
They contain few craters because they formed after most impacts had occurred.
Part J - Quiz Question 10
Which of the following best describes the geological histories of the Moon and Mercury?
Hint 1.
Study Section 7.2 of The Essential Cosmic Perspective
.
ANSWER:
Greenhouse gases absorb X-rays and ultraviolet light from the Sun, and this absorbed radiation then heats the atmosphere and the surface.
Greenhouse gases absorb infrared light coming from the Sun, and this absorbed sunlight heats the lower atmosphere and the surface.
A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which
thereby heats the lower atmosphere.
The greenhouse effect is caused primarily by ozone, which absorbs ultraviolet light and thereby makes the atmosphere much hotter than it would be otherwise.
about the same as it is now
slightly cooler, but still above freezing
well below the freezing point of water
slightly warmer, but still well below the boiling point of water
The maria
formed within the past 1 billion years.
The maria
formed after the heavy bombardment ended.
The regions of the maria
were hit by fewer impacts than the densely cratered regions.
Erosion affects the maria
more than it affects other regions of the Moon.
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That pretty much summarizes the geological histories of the Moon and Mercury.
Part K - Quiz Question 11
What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
Hint 1.
Study Section 7.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
If water really did flow, the atmospheric conditions must have been different.
Part L - Quiz Question 12
All the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space?
Hint 1.
Study Section 7.3 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This allowed the solar wind to strip atmospheric gas into space.
Part M - Quiz Question 13
Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
Hint 1.
Study Section 7.4 of The Essential Cosmic Perspective
.
ANSWER:
All four geological processes were important in their early histories, but only impact cratering still reshapes their surfaces today.
Impact cratering shaped these worlds early in their histories. Then, during the past few million years, they were reshaped by episodes of volcanism and tectonics.
Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
Impact cratering is the only major geological process that has affected their surfaces.
The presence of inactive volcanoes on Mars tells us that there must once have been a lot of outgassing, and hence a thicker atmosphere.
We think it for purely theoretical reasons, based on calculations showing that the Sun has brightened with time.
The fact that parts of Mars have a lot of craters tell us that Mars must once have been much warmer.
The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.
Mars lost any global magnetic field that it may once have had.
The axis tilt of Mars is thought to change significantly with time.
Mars probably once had a much higher density of greenhouse gases in its atmosphere than it does today.
Outgassed water molecules are split apart, and the oxygen then reacts chemically with surface rock on Mars.
The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle
The smaller size of Venus, which has allowed it to lose much more internal heat than Earth
The slow rotation of Venus
The apparent lack of plate tectonics on Venus
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Without water, the rock would be stronger and the lithosphere could become thicker.
Part N - Quiz Question 14
All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
Hint 1.
Study Section 7.4 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This suggests that older impact craters were covered over everywhere on the planet.
Part O - Quiz Question 15
Which of the following best explain what we think happened to outgassed water vapor on Venus?
Hint 1.
Study Section 7.4 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This did not occur on Earth, because the temperatures allowed the water vapor to condense into liquid water and rain down to the surface.
Part P - Quiz Question 16
Why are there fewer large impact craters on the Earth's seafloor than on the continents?
Hint 1.
Study Section 7.5 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Seafloor crust is continually recycled, so that the seafloor is nearly everywhere younger than about 200 million years. Therefore evidence of any earlier impacts has been erased
as the seafloor crust was recycled.
Part Q - Quiz Question 17
Which two factors are most important to the existence of plate tectonics on Earth?
Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle.
Venus has many circular features, called coronae
, which appear to be tectonic in origin.
Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
Venus's largest features are three elevated regions that look somewhat like continents.
Water was removed from the atmosphere by chemical reactions with surface rock.
Ultraviolet light split the water molecules, and the hydrogen then escaped to space.
It is frozen as water ice in craters near the poles.
It turned into carbon dioxide by reacting with nitrogen in Venus's atmosphere.
Erosion erases impact craters must faster on the ocean bottom than on land.
Most impacts occur on the land.
The oceans slow large impactors and prevent them from making craters.
The crust on seafloors is younger than on continents, so it has had less time in which to suffer impacts.
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Hint 1.
Study Section 7.5 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Mantle convection helps move the plates, and the plates probably exist because the lithosphere was thin enough to break into these plates.
Part R - Quiz Question 18
Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
Hint 1.
Study Section 7.5 of The Essential Cosmic Perspective
.
ANSWER:
Correct
The carbon dioxide became locked up like this on Earth after it dissolved in water and combined with minerals to make carbonate rock. This does not occur on Venus because
there is no liquid water.
Part S - Quiz Question 19
Which two factors are critical to the existence of the carbon dioxide (CO
2
) cycle on Earth?
Hint 1.
Study Section 7.5 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Carbon dioxide dissolves in the oceans and becomes incorporated into carbonate rock; plate tectonics recycles the carbonate rock into the mantle, where it melts and releases its
gas back to the atmosphere.
Part T - Quiz Question 20
Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?
Hint 1.
Study Section 7.5 of The Essential Cosmic Perspective
.
ANSWER:
Earth's liquid outer core and solid inner core
oxygen in the atmosphere and mantle convection
mantle convection and a thin lithosphere
the existence of life and oxygen in the atmosphere
Chemical reactions turned Earth's carbon dioxide into nitrogen.
Earth's volcanoes outgassed far less carbon dioxide than those on Venus.
Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere.
Earth once had a lot of carbon dioxide, but it was lost to space during the heavy bombardment early in our solar system's history.
Plate tectonics and liquid water oceans
Active volcanism and active tectonics
Life and atmospheric oxygen
Life and active volcanism
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This feedback mechanism would indeed warm the planet back up.
Part U - Quiz Question 21
Which of the following correctly lists two key pieces of evidence that, together, indicate that we should expect
human activity to cause global warming
?
Hint 1.
Study Section 7.5 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Given these two indisputable facts, we should expect that Earth will warm up as we continue to add carbon dioxide to the atmosphere.
Part V - Quiz Question 22
The choices that follow describe four hypothetical planets. Which one would you expect to have the hottest
interior
? (Assume the planets orbit a star just like the Sun and that they are all
the same age as the planets in our solar system.)
Hint 1.
Consider all that you've learned Chapter 7 of The Essential Cosmic Perspective
.
ANSWER:
Correct
Largest size means the highest interior temperature.
Part W - Quiz Question 23
The choices that follow describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters
? (Assume the planets orbit a star just like the Sun
and that they are all the same age as the planets in our solar system.)
Hint 1.
Consider all that you've learned Chapter 7 of The Essential Cosmic Perspective
.
ANSWER:
Cooler temperatures allow carbon dioxide to form rain and rain out of the atmosphere.
Cooler temperatures mean more ice and more erosion, which somehow makes the planet warm up.
Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the
greenhouse effect.
Cooler temperatures cause volcanoes to become more active, so they release more carbon dioxide into the atmosphere than they do when temperatures are warmer.
(1) We can learn about past climate from ice cores; (2) ice cores show that Earth naturally has cooler and warmer periods.
(1) Carbon dioxide tends to make planets warmer than they would be otherwise; (2) measurements demonstrate that human activity is raising the carbon dioxide concentration in
the atmosphere.
(1) The carbon dioxide cycle regulates Earth's climate; (2) human activity has disrupted the carbon dioxide cycle.
(1) The burning of fossil fuels is a form of human activity; (2) human activity is always bad for the environment.
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
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The smallest size means the least geological activity to have erased past impact craters, so lots of craters would still be present.
Part X - Quiz Question 24
The choices that follow describe four hypothetical planets. Which one would you expect to have the most features of erosion
? (Assume the planets orbit a star just like the Sun and that they
are all the same age as the planets in our solar system.)
Hint 1.
Consider all that you've learned in Chapter 7 of The Essential Cosmic Perspective
.
ANSWER:
Correct
This planet is large enough to have had outgassing make an atmosphere and rotates fast enough to drive winds.
Formation of the Solar System Tutorial
This tutorial will help you understand how our solar system was formed and what factors lead to the differences between planets.
Launch the Formation of the Solar System tutorial. Answer the ungraded questions in the tutorial and the graded follow-up questions below.
Part A
The planets in our solar system are thought to have come from
ANSWER:
Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
clumps of rocky material that exist between stars.
the same cloud of gas and dust in which the Sun formed.
the Sun (they were flung out from the spinning Sun).
a cloud of gas in the Orion nebula.
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Part B
As the solar nebula collapsed, it became a disk because
ANSWER:
Correct
Part C
The inner planets are small and rocky and the outer planets are mostly large and gaseous because
ANSWER:
Correct
Part D
The temperature of the protoplanetary disk allowed
ANSWER:
Correct
Part E
As the solar nebula collapsed under its own gravity,
ANSWER:
Correct
Part F
Suppose the solar nebula had cooled much more before the solar wind cleared away the remaining gas. In that case, the terrestrial planets likely would have ended up
ANSWER:
the self-gravity of the nebula pulled the material into the ecliptic plane.
the Sun’s gravity pulled the nebula material into the ecliptic plane.
collisions between particles made the particles go in more-or-less the same direction.
the initial cloud was disk shaped.
hydrogen is more abundant than rocks and metals so that beyond the frost line hydrogen froze to form the jovian planets.
the spin of the disk caused the denser rock and metals to remain towards the center of the solar system, while the lighter material were flung farther from the Sun.
hydrogen compounds are more abundant than rocks and metals so that beyond the frost line the gravity of large ice planetesimals could capture the abundant light gases.
the Sun’s gravity caused the denser rock and metals to settle towards the center of the solar system while the lighter materials remained farther from the Sun.
hydrogen compounds, rocks, and metals to freeze in the inner region only.
rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds to freeze only in the outer region.
rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds and H/He gases to freeze only in the outer region.
rocks and metals to freeze in the inner region only, and hydrogen compounds to freeze in the outer region only.
it cooled down and spun down.
it heated up and spun down.
it heated up and spun up.
it cooled down and spun up.
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Part G
If the solar nebula initially had no angular momentum,
ANSWER:
Correct
Part H
Suppose the solar nebula had been too warm for ices to condense anywhere. If a planet had still formed at Jupiter's location, it most likely would have
ANSWER:
Correct
Surface Temperature of Terrestrial Planets Tutorial
This tutorial will help you understand the factors that affect the surface temperature of terrestrial planets.
Launch the Surface Temperature of Terrestrial Planets tutorial. Answer the ungraded questions in the tutorial and the graded follow-up questions below.
Part A
What is the main reason Mercury is much hotter than the Moon?
ANSWER:
with a higher abundance of hydrogen compounds and larger size.
being made entirely of H/He gas.
with a higher abundance of metals and larger size.
the same as they are now.
the planets would orbit closer to the Sun.
the planets would orbit farther away from the Sun.
there would not be any planets orbiting the Sun.
been similar in composition to Earth, with a much smaller mass than the real Jupiter.
turned out pretty much the same as the real Jupiter.
been smaller in mass than the real Jupiter, but still made mostly of H/He.
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Part B
Greenhouse gases
ANSWER:
Correct
Part C
What would the temperature of a planet be if its reflectivity were 1.0?
ANSWER:
Correct
Part D
Mars's surface temperature would be higher if
ANSWER:
Correct
Part E
Which of the following gases are greenhouse gases?
ANSWER:
Mercury has a slower rotation rate.
Mercury has a lower albedo than the Moon.
Mercury is closer to the Sun.
Mercury has more greenhouse gases than the Moon.
absorb infrared light and transmit visible light.
absorb X-rays and transmit infrared light.
absorb ultraviolet light and transmit visible light.
absorb visible light and transmit infrared light.
It would be very, very cold.
It could be cold or warm, depending on the distance from the Sun.
It could be cold or warm, depending on the amount of greenhouse gases.
It would be very, very hot.
it were farther from the Sun.
it rotated more quickly.
its reflectivity were higher.
its atmosphere contained more greenhouse gases.
Carbon dioxide and nitrogen
Oxygen and carbon dioxide
Water and oxygen
Carbon dioxide and water
Oxygen and nitrogen
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Part F
If Venus's atmosphere contained the same amount of greenhouse gases as Earth's atmosphere, its surface temperature would be
ANSWER:
Correct
Score Summary:
Your score on this assignment is 98.9%.
You received 44.51 out of a possible total of 45 points.
slightly colder
significantly colder
significantly warmer
slightly warmer
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