Astronomy Chapter 9 Part One

This figure summarizes the geological histories of the terrestrial worlds. Based on this figure, what can you conclude?

The most important factor in a planet's geological history is its size.

Under what circumstances can differentiation occur in a planet?

The planet must have a molten interior.

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

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

Why are there fewer large craters on the seafloor than on the continents?

The seafloor crust is younger than the continental crust.

This image shows two tall volcanoes on Venus. Why is it yellow?

The yellow color is arbitrary because this image was created with radar data rather than visible light.

How have we been able to construct detailed maps of surface features on Venus?

by using radar from spacecraft that were sent to orbit Venus

The core, mantle, and crust of a planet are defined by differences in their

composition

What drives the motion of the tectonic plates on Earth?

convection cells in the mantle

As a general rule, smaller planets __________ than larger planets.

cool more rapidly

From center to surface, which of the following correctly lists the interior layers of a terrestrial world?

core, mantle, crust

Which two properties are most important in determining the surface temperature of a planet?

distance from the Sun and atmosphere

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

has a large size for a terrestrial planet.

Volcanism is more likely on a planet that

has high internal temperatures.

A planet is most likely to have tectonic activity if it has

high internal temperature.

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

impact cratering and erosion

The processes responsible for virtually all surface geology are _________.

impact cratering, volcanisms, tectonics, and erosion

Scientists can estimate the age of a planetary surface by counting __________.

impact craters

Heat escapes from a planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the

infrared

The terrestrial planet cores contain mostly metal because

metals sank to the center during a time when the interiors were molten throughout.

The polar caps on Mars are composed of

mostly solid carbon dioxide and some water ice.

The existence of a core-mantle-crust interior structure tells us that a world __________.

once had a molten interior

How many of the five terrestrial worlds have surfaces being constantly reshaped by plate tectonics?

one

What process has shaped Earth's surface more than any other?

plate tectonics

Which internal energy source is the most important in continuing to heat the terrestrial planets today?

radioactivity

Which of the following best describes the lunar maria?

relatively smooth, flat plains on the Moon

Olympus Mons is a

shield volcano on Mars.

Which of a planet's fundamental properties has the greatest effect on its level of volcanic and tectonic activity?

size

The Caloris Basin on Mercury covers a large region of the planet, but few smaller craters have formed on top of it. From this we conclude that

the Caloris Basin formed toward the end of the solar system's period of heavy bombardment.

What type of stresses broke Earth's lithosphere into plates?

the circulation of convection cells in the mantle, which dragged against the lithosphere

Which of the following describes tectonics?

the disruption of a planet's surface by internal stresses

Which of the following describes impact cratering?

the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface

Which of the following is NOT an example of tectonics?

the gradual disappearance of a crater rim as a result of wind and rain

Which of the following does not provide evidence that Mars once had large amounts of flowing water?

the presence of vast canals discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell

What is differentiation in planetary geology?

the process by which gravity separates materials according to density

When we see a region of a planet that is not as heavily cratered as other regions, we conclude that

the surface in the region is younger than the surface in more heavily cratered regions.

Which of the following describes erosion?

the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather

The relatively few craters that we see within the lunar maria

were formed by impacts that occurred after those that formed most of the craters in the lunar highlands.

Which of the following most likely explains why Venus does not have a strong magnetic field?

Its rotation is too slow.

How did the lunar maria form?

Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins.

Which of the following show evidence of ancient river beds?

Mars

This photo was taken from orbit around some planet. What planet is it, and how do you know?

Mars because we see dried up riverbeds

Rank the five terrestrial worlds in order of size from smallest to largest.

Moon, Mercury, Mars, Venus, Earth

The arrow in this photo is pointing at a feature known as _____________________.

Olympus Mons

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

Olympus Mons

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

Surface water only exists as frozen ice.

The major processes that heat the interiors of the terrestrial worlds are __________.

(1) heat deposited as the planets were built from planetesimals (2) heat deposited as the planets underwent differentiation (3) heat released by radioactive decay

In the context of plate tectonics, what is a subduction zone?

a place where a seafloor plate is sliding under a continental plate

Shown following are three terrestrial planets of our solar system. Rank the planets based on the amount of time the surface of the planet has had a moderate to high level of volcanic/tectonic activity, from longest to shortest.

-Earth -Mars -Mercury

Percival Lowell's claims of a Martian civilization generated great public interest, but other scientists of his time were highly skeptical of these claims. Which two of the following statements (which are all true) explain why other scientists of the late 19th and early 20th centuries rejected Lowell's claims?

-Lowell's canals did not appear in photographs of Mars taken through telescopes. -Lowell's canals followed perfectly straight lines for thousands of kilometers.

Shown below are the four terrestrial planets of our solar system. Assume that all the planets started out equally hot inside. Rank the planets based on their expected cooling rates, from fastest cooling to slowest cooling.

-Mercury -Mars -Venus -Earth

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

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

Now go to the screen "Major Geological Features," and explore the main screen with labels on and off and elevation on and off. Then complete the sentences below. Drag words from the left to the correct blanks at the right.

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

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

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

Which of the following statements about our solar system's terrestrial worlds are true?

-Their interiors all have a core, mantle, and crust. -They are all made primarily of rock and metal. -They are all of nearly the same age.

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

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

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.

-active volcanoes -an atmosphere produced by outgassing -active tectonics

Which feature in this photo of the full moon is one of the lunar maria?

1

Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.

1. The slowly increasing distance between South America and Africa is due to seafloor spreading. 2. Old Faithful Geyser at Yellowstone National Park in the United States acquires its energy from a hot spot. 3. Layered sedimentary rock exposed by erosion can be seen when looking at the Grand Canyon in the United States. 4. Australia is composed of relatively old and thick continental crust. 5. The extremely deep ocean Marianas Trench is a result of subduction. 6. Seafloor crust found in the Atlantic Ocean between North America and Europe is composed of dense and relatively young rock. 7. The earthquakes that occur in Southern California generally occur above a fault.

About how large (on average) is an impact crater compared to the size of the impactor?

10 times larger

This diagram represents the conveyor-like action of plate tectonics on Earth. Which numbered position represents a place where new seafloor crust is being made?

2

The image below shows a rock formation nicknamed "the face on Mars" that was taken by the Viking 1 orbiter in 1976. Given the clear resemblance to a face, what is an appropriate scientific reaction to this image?

Assume it is most likely a coincidental result of light and shadow, and plan higher resolution follow-up observations.

Which of the terrestrial worlds has the strongest magnetic field?

Earth

Choose the correct description of the conveyor-like action of plate tectonics on Earth.

Earth's lithosphere is broken up into plates that float on the underlying mantle. The tops of the mantle's convection cells drag the bottoms of the plates, making them move. This movement causes spreading in some places and subduction in others.

The magnetic and rotational north poles on Earth are the same.

False

There is no erosion of surface features on the Moon.

False

Each of the following statements is best associated with one of the four major geological processes. Drag each statement into the correct bin for its associated process. Drag the appropriate items to their respective bins.

Impact Cratering -mostly occurred during heavy bombardment -affected all solid worlds similarly Volcanism -erased virtually all crater on Io -responsible for the existence of Earth's atmosphere and oceans -created the smooth lunar maria Tectonics -on earth, involves motion of plates -includes surface compression that builds mountains Erosion -includes features sculpted by winds

How does the amount of heat released in a planet's interior by radioactive decay change with time?

It drops off with time.

Why does Earth have the strongest magnetic field among the terrestrial worlds?

It is the only one that has both a partially molten metallic core and reasonably rapid rotation.

Which of the following best describes convection?

It is the process in which warm material expands and rises while cool material contracts and falls.

Which describes our understanding of flowing water on Mars?

It was important once, but no longer.

Why does the Moon have a layer of powdery "soil" on its surface?

It's the result of gradual erosion by micrometeorites striking the Moon.

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?

Its core is too cool for convection.

Each statement below represents a feature that has been claimed to exist on Mars. Sort the statements into the correct bin according to whether each is a feature that actually exists, that does not actually exist, or that might exist but about which we cannot yet draw a definitive conclusion.

Real Mars -minerals of types known to form in liquid water -dried-up river beds -abundant water ice Imaginary Mars -cities built by an ancient civilization -frequent rainfall and snowfall -surface pools of liquid water -a network of straight-line canals Unknown Mars -microscopic life -underground pockets of liquid water

Spacecraft have landed on all the terrestrial worlds except

Spacecraft have landed on all of the terrestrial worlds.

Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones?

They have relatively more surface area compared to their volumes.

What is the significance of the yellow lines on this map of Earth?

They represent boundaries between the plates that make up Earth's lithosphere.

Why do we think Mercury has so many tremendous cliffs?

They were probably formed by tectonic stresses when the entire planet shrank as its core cooled.

These four photos show features of Earth that change with time, some fast and some slow. Which one of these features is being shaped primarily by the process we call tectonics?

This photo shows the Himalayas, which were built by plate tectonics.

This photo from the Curiosity rover shows what appears to be layered sedimentary rock on Mars. What does this photo seem to be telling us?

This region of Mars once held a body of water such as a lake.

Earth is the only planet in the solar system known to have plate tectonics.

True

Mars has virtually no magnetic field.

True

Spacecraft have landed on all of the terrestrial worlds.

True

Valles Marineris is a

Valles Marineris is a

What do we mean when we say that the terrestrial worlds underwent differentiation?

When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.

What do we mean when we say that the terrestrial worlds underwent differentiation?

When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces. Submit

What are the basic requirements for a terrestrial world to have a global magnetic field?

a core layer of molten, convecting material and sufficiently rapid rotation

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

a faster rotation rate

How fast do plates move on Earth?

a few centimeters per year

Based on its surface features, the most important event on Venus in the past billion years or so was _______.

a global "repaving" that erased essentially all the surface features that had existed earlier

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

a greater distance from its star

A terrestrial world's lithosphere is ________.

a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle

The three principal sources of internal heat of terrestrial planets are

accretion, differentiation, and radioactivity.

What kind of surface features may result from tectonics?

all of the above

The geological feature in this photo is _________.

an impact crater

Which internal energy source produces heat by converting gravitational potential energy into thermal energy?

both A and B (accretion and differentiation)

What are the conditions necessary for a terrestrial planet to have a strong magnetic field?

both a molten metallic core and reasonably fast rotation