Astronomy Final Exam

The two most important processes in heating the interiors of the terrestrial worlds are:

1. Heat deposited by the process of formation. 2. Heat released by radioactive decay.

Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is _______.

About the thickness of a sheet of paper.

On average, how fast do the plates move on the Earth?

A few centimeters per year.

Which of the following is the most basic definition of a greenhouse gas?

A gas that absorbs infrared light.

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.

Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of ___________.

A golf ball to a basketball.

What do we mean by a runaway greenhouse effect?

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

Olympus Mons is _______.

A huge volcano on Mars.

The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that ________.

A large baked potato takes longer to cool than a small baked potato.

A terrestrial world's lithosphere is _______.

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

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

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

Which of the following best describes how the greenhouse effect works?

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.

What is a magnetosphere?

A region of space around a planet in which the planet's magnetic field can trap charged particles.

Why is the sky blue on Earth?

Because molecules scatter blue light more effectively than red light.

In general, which things below are affected by a magnetic field?

Charged particles or magnetized materials (such as iron).

Why is Mars red?

Chemical reactions between surface rock and atmospheric oxygen literally rusted the surface.

Why is Earth's continental crust lower in density than seafloor crust?

Continental crust is made as the lowest density seafloor crust melts and erupts to the surface near subduction zones.

Suppose Earth were to cool down a little. How would the carbon dioxide cycle lend to restore temperatures to normal?

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.

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

Core, mantle, crust.

Which of the following best describes the geological histories of the Moon and Mercury?

Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.

Why does Earth have so little carbon dioxide in its atmosphere compared to 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.

Which internal heat source still generates heat within the terrestrial worlds today?

Heat from radioactive decay.

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

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

The processes responsible for virtually all surface geology are __________.

Impact cratering, volcanoes, tectonics, and erosion.

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

It is the result of countless tiny impacts by small particles striking the Moon.

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

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

How does seafloor crust differ from continental crust?

Seafloor crust is thinner, younger, and higher in density.

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

Its rotation is too slow.

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

Its size.

Which of the following is the underlying reason why Venus has so little wind erosion?

Its slow rotation.

What's the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead?

Its small size compared to Earth.

Which two factors are most important to the existence of plate tectonics on Earth?

Mantle convection and a thin lithosphere.

All of the following statements about Mars are true. which one might have led to significant loss of atmospheric gas to space?

Mars lost any global magnetic field that it may once have had.

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?

Mars' interior has cooled so much its molten core layer no longer undergoes convection.

The cores of the terrestrial worlds are made mostly of metal because ________.

Metals sunk to the centers a long time ago when the interiors were molten throughout.

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?

Not much - On human time scales, the mantle looks like solid rock.

Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?

Plate tectonics and liquid water oceans.

What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?

Plate tectonics and widespread erosion.

Which of the following best describes the lunar maria?

Relatively smooth, flat plains on the Moon.

Why are there fewer large impact craters on the Earth's seafloor than on the continents?

Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.

The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion?

Size: same as Venus, Distance from Sun: same as Mars, Rotation Rate: once every 25 hours.

The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters?

Size: same as the Moon, Distance from Sun: same as Mars, Rotation Rate: Once every 10 days.

The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior?

Size: twice as big as Earth, Distance from Sun: same as Mercury, Rotation Rate: Once every 6 months.

Which of the following general statements about Earth's atmosphere is not true?

The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.

What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?

The atmosphere is too cold and think for liquid water today, yet we see evidence that water flowed on the surface in the past.

Which of the following is not an expected consequence of global warming?

The entire Earth will warm up by the same amount.

Which of the following is not an example of tectonics?

The gradual disappearance of a crater rim as a result of wind and rain.

Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?

The high surface temperature that has "baked out" all the liquid water from Venus' crust and mantle.

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?

The maria formed after the heavy bombardment ended.

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

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

What observational evidence supports the idea that Mercury once shrank by some 20 km in radius?

The presence of many long, tall cliffs.

In the context of planet geology, what do we mean by outgassing?

The release by volcanism of gases that had been trapped in a planetary interior.

Which of the following best explains what we think happened to outgassed water vapor on Venus?

Ultraviolet light split the water molecules, and the hydrogen then escaped into space.

All of the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450 C hotter than the surface of Earth?

Venus has a much stronger greenhouse effect than Earth.

All of the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?

Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.

Which of the following is an example of convection?

Warm air expanding and rising while cooler air contracts and falls.

Suppose that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be _________.

Well below the freezing point of water.

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.