Astronomy 207 Midterm 4 ~ UofC

5) Why do asteroids and comets differ in composition?
A) Asteroids formed inside the frost line, while comets formed outside.
B) Asteroids and comets formed at different times.
C) Comets formed from the jovian nebula, while asteroids did not.
D) Comets are much larger than asteroids.
E) Asteroids are much larger than comets.

A) Asteroids formed inside the frost line, while comets formed outside.

Why aren't small asteroids spherical in shape?
A) The strength of gravity on small asteroids is less than the strength of the rock.
B) Small asteroids have odd shapes because they were all chipped off larger objects.
C) Large asteroids were once molten and therefore became spherical, but small asteroids were never molten.
D) Large asteroids became spherical because many small collisions chipped off pieces until only a sphere was left; this did not occur with small asteroids.

A) The strength of gravity on small asteroids is less than the strength of the rock.

Where are the Trojan asteroids located?
A) surrounding Jupiter
B) along Jupiter's orbit, 60° ahead of and behind Jupiter
C) in the center of the asteroid belt
D) on orbits that cross Earth's orbit
E) on orbits that cross Mars's orbit

B) along Jupiter's orbit, 60° ahead of and behind Jupiter

How do we know that there are large gaps in the average distances of asteroids from the Sun (within the asteroid belt)?
a) We can see the gaps through telescopes.
b)We can identify the gaps by looking for stellar occultations in which an asteroid passed in front of a star as seen from Earth.
c) We have not actually detected any gaps, but theory says they must exist.
d) We know the gaps must be present to explain how our spacecraft have successfully navigated the asteroid belt without suffering collisions.
e) We notice gaps on graphs showing the distribution of asteroids with different orbital periods.

e) We notice gaps on graphs showing the distribution of asteroids with different orbital periods.

The number of comets in the Oort cloud is probably about
A) a thousand.
B) a million.
C) a billion.
D) a trillion.
E) a quintillion.

D) a trillion.

Which of the following does not lend support to the idea that Pluto is a Kuiper-belt object?
A) Pluto has a cometlike composition and density.
B) Pluto is regarded by many to be a planet.
C) Some asteroids have their own moons.
D) Pluto has a more eccentric orbit than other planets.
E) Some known Kuiper-belt objects are hundreds of kilometers across.

b) Pluto is regarded by many to be a planet.

Based on its orbit, Pluto is a large member of
a) the asteroid belt.
b) the Oort cloud.
c)the moon system around Neptune.
d) an extrasolar planetary system.
e) the Kuiper belt.

e) the Kuiper belt.

On average, how often do impactors about 10 km in size, large enough to produce mass extinction, hit Earth?
A) once every century
B) once every thousand years
C) once every million years
D) once every hundred million years
E) once in Earth's history

D) once every hundred million years

How can we determine the reflectivity of an asteroid?
a) by taking a photograph of it
b) by measuring its mass and radius c) by where it is located in the asteroid belt
d) by comparing its brightness in visible light to its brightness in infrared light

d) by comparing its brightness in visible light to its brightness in infrared light

When a comet is within the inner solar system, its visible tails point
a) opposite the direction the comet is moving in its orbit
b) perpendicular to the ecliptic plane
c) always almost due north
d) in the direction the comet is moving in its orbit
e) away from the Sun

e) away from the Sun

What caused Earth's lithosphere to fracture into plates?
a) impacts of asteroids and planetesimals
b)internal temperature changes that caused the crust to expand and stretch
c) tidal forces from the Moon and Sun
d) volcanism, which produced heavy volcanoes that bent and cracked the lithosphere
e) convection of the underlying mantle

e) convection of the underlying mantle

How fast do plates move on Earth?
A) a few centimeters per year
B) a few millimeters per century
C) a few kilometers per century
D) quite fast, but only during earthquakes
E) about 1 mile per hour

A) a few centimeters per year

Ridges in the middle of the ocean are places where
A) one plate slides under another, returning older crust to the mantle.
B) hot mantle material rises upward, creating volcanic islands.
C) hot mantle material rises upward and spreads sideways, pushing the plates apart.
D) plates push together, creating ocean mountain chains.
E) plates slip sideways relative to one another.

C) hot mantle material rises upward and spreads sideways, pushing the plates apart.

Deep trenches in the ocean mark places where
A) one plate slides under another, returning the older crust to the mantle.
B) plates pull apart, leaving great rifts in the crust.
C) hot mantle material rises upward and spreads sideways, pushing the plates apart.
D) plates push together, creating ocean mountain chains.
E) plates slip sideways relative to one another.

E) plates slip sideways relative to one another.

How does seafloor crust differ from continental crust?
A) Seafloor crust is thicker, older, and higher in density.
B) Seafloor crust is thinner, younger, and higher in density.
C) Seafloor crust is thinner, older, and lower in density.
D) Seafloor crust is thicker, older, and lower in density.
E) Seafloor crust is thicker, younger, and lower in density.

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

Which of the following regions was the result of plumes of hot mantle rising in a hot spot within a plate?
A) Alaska's Aleutian Islands
B) Japan and the Philippines
C) the islands of Hawaii
D) the volcano Mount St. Helens
E) all of the above

C) the islands of Hawaii

Why are there fewer large impact craters on Earth's seafloor than on the continents?
a) The oceans slow large impactors and prevent them from making craters.
b) Erosion erases impact craters must faster on the ocean bottom than on land.
c) Most impacts occur on the land.
d) Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.

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

How does the greenhouse effect work?
A) Greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light from Earth, trapping the heat near the surface.
B) The higher pressure of the thick atmosphere at lower altitudes traps heat in more effectively.
C) Ozone transmits visible light, allowing it to heat the surface, but then absorbs most of the infrared heat, trapping the heat near the surface.
D) Greenhouse gases absorb X rays and ultraviolet light from the Sun, which then heat the atmosphere and the surface.
E) Greenhouse gases absorb infrared light from the Sun, which then heats the atmosphere and the surface.

A) Greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light from Earth, trapping the heat near the surface.

Suppose Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be
A) 250 K, which is well below freezing.
B) 273 K, or about the freezing point for water.
C) 283 K, or about 5 K cooler than it is now.
D) 288 K, or about the same as it is now.
E) 293 K, or about 5 K warmer than it is now.

A) 250 K, which is well below freezing.

Heat escapes from a planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the
A) infrared.
B) radio.
C) visible.
D) ultraviolet.
E) none of the above

A) infrared.

What kind of thermal radiation does Earth emit?
a) visible and ultraviolet light
b) infrared and visible light
c) infrared, visible, and ultraviolet light
d) visible light
e) infrared light

e) infrared light

Earth's stratosphere is heated primarily by which process?
A) Convection from the Earth's surface.
B) Absorption of infrared radiation by greenhouse gases.
C) Absorption of visible light by ozone.
D) Absorption of ultraviolet radiation by ozone.
E) Atoms and molecules absorb infrared sunlight.

D) Absorption of ultraviolet radiation by ozone.

Convection occurs in the troposphere but not in the stratosphere because
A) the troposphere is warmer than the stratosphere.
B) the troposphere is cooler than the stratosphere.
C) lower altitudes of the troposphere are warmer than higher altitudes, unlike in the stratosphere.
D) higher altitudes of the troposphere are warmer than lower altitudes, unlike in the stratosphere.
E) the troposphere contains fewer greenhouse gases than the stratosphere.

E) the troposphere contains fewer greenhouse gases than the stratosphere.

Why are sunsets and sunrises red?
a) The Sun emits more red light when it's near the horizon.
b) Sunlight must pass through more atmosphere to reach our eyes at those times, which means it passes through a larger volume of red air molecules.
c) The lower temperatures of morning and evening (compared to midday) make the sky redder in color.
d) Sunlight must pass through more atmosphere to reach our eyes at those times, so more blue light is scattered away.

d) Sunlight must pass through more atmosphere to reach our eyes at those times, so more blue light is scattered away.

Why does convection occur in the troposphere, but not in the stratosphere?
a) The troposphere is warmer than the stratosphere.
b) The troposphere is cooler than the stratosphere.
c) Density decreases with altitude in the troposphere, but this trend reverses in the stratosphere.
d) The troposphere contains a smaller proportion of greenhouse gases than the stratosphere.
e) Temperature decreases with altitude in the troposphere, but this trend reverses in the stratosphere.

e) Temperature decreases with altitude in the troposphere, but this trend reverses in the stratosphere.

Earth has gone in and out of numerous ice ages over the past couple million years. Which of the following was generally true during all those ice ages?
a) The atmospheric carbon dioxide concentration was much higher than it is today.
b) The continents were closer together than they are today.
c) The continents were farther apart than they are today.
d) There were much larger mammals than there are today.
e) The atmospheric carbon dioxide concentration was much lower than it is today.

e) The atmospheric carbon dioxide concentration was much lower than it is today.

Geological evidence points to a history of extended ice ages in Earth's history. How did Earth recover from this snowball phase?
A) The increased ice coverage on Earth's surface absorbed more sunlight than water and rocks, thus gradually heating Earth until the ice melted.
B) Life vanished, leading to an increase in CO2, and increased global warming, eventually melting the ice.
C) Volcanoes continued to inject CO2 into Earth's atmosphere, increasing the greenhouse effect to the point where ice melted.
D) Plate tectonics gradually subducted all the ice below Earth's surface.
E) As the Sun aged, it grew brighter and increased Earth's temperature, melting the ice.

C) Volcanoes continued to inject CO2 into Earth's atmosphere, increasing the greenhouse effect to the point where ice melted.

Where did the molecular oxygen in Earth's atmosphere come from?
Question 39 options:
a) photosynthesis by living organisms
b) outgassing from volcanoes
c) evaporation from the oceans
d) chemical reactions with surface rocks
e) the breakdown of water molecules by sunlight

a) photosynthesis by living organisms

Why do jovian planets bulge around the equator, that is, have a "squashed" appearance?
A) They are much more massive than the terrestrial planets.
B) Their large systems of moons and rings gravitationally attract the mass around the equator more.
C) Their rapid rotation flings the mass near the equator outward.
D) Their internal heat sources exert a pressure against the sides of the planets.
E) all of the above

C) Their rapid rotation flings the mass near the equator outward.

Which jovian planets have compositions dominated by hydrogen compounds such as methane, ammonia, and water?
a) Saturn and Uranus
b) Jupiter and Neptune
c) Saturn, Uranus, and Neptune
d) Saturn and Neptune
e) Uranus and Neptune

e) Uranus and Neptune

Why is Jupiter denser than Saturn?

A) It is made of a different composition than Saturn, including a higher proportion of hydrogen compounds and rocks.
B) The extra mass of Jupiter compresses its interior to a greater extent than that of Saturn.
C) Its core is much larger than Saturn's.
D) It has a greater proportion of helium to hydrogen compared to Saturn.
E) It is unknown why this is so.

B) The extra mass of Jupiter compresses its interior to a greater extent than that of Saturn.

Why does Jupiter have several distinct cloud layers?

A) Different layers represent clouds made of gases that condense at different temperatures.
B) Different layers represent the various regions where the temperature is cool enough for liquid water to condense.
C) Different gases are present at different altitudes in Jupiter's atmosphere.
D) Winds prevent clouds from forming at some altitudes, so we see clouds only at the other altitudes.
E) Clouds form randomly, so on average there are always several layers.

A) Different layers represent clouds made of gases that condense at different temperatures.

Which of the following would be the strongest clue that a rock you have found is a meteorite rather than a terrestrial rock?

A) It contains a lot of iron.
B) It is dark colored.
C) It contains elements and isotopes in proportions that are rare on Earth but common in asteroids.
D) It is too heavy for you to hold in your hand.

C) It contains elements and isotopes in proportions that are rare on Earth but common in asteroids.

Why are collisions between asteroids in the asteroid belt rare?

a) All asteroids orbit in perfect circular orbits at the same speed.
b) Jupiter's gravity keeps asteroids apart.
c) The gas surrounding the asteroids help them repel each other before colliding.
d) There are only a few asteroids in the solar system.
e) The average distance between asteroids is millions of kilometres.

e) The average distance between asteroids is millions of kilometres.

How can meteorites from the Moon or Mars have made it to Earth?

a) Those worlds spin rapidly enough to have sent some rocks from their surfaces into space.
b) The meteorites from the Moon and Mars were never actually part of those worlds; they are just rocks that formed in the same vicinities of the solar system.
c) The solar wind gradually blew material off of the surfaces of these worlds, and once in space it collected together to make the meteorites.
d) Impacts on those worlds blasted rocks into space that eventually fell to Earth.

d) Impacts on those worlds blasted rocks into space that eventually fell to Earth.

According to the nebular theory, how did the Kuiper belt form?
a) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.
b) It consists of objects that fragmented from the Sun during a catastrophic collision early in the formation of the solar system.
c) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.
d) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.
e) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.

e) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.

According to the nebular theory, how did the Oort cloud form?

a) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.
b) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.
c) It consists of objects that fragmented from the Sun during a catastrophic collision early in the formation of the solar system.
d) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.
e) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

e) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

Which of the following was the first strong evidence for an asteroid impact being the cause of the extinction of the dinosaurs 65 million years ago (as well as 75% of all species alive at the time)?

a) the discovery of asteroid fragments in dinosaur bones dating to that time
b) the fact that dinosaurs appear to have gone abruptly extinct at about that time
c) careful studies of lunar craters suggesting an unusually large number of impact at that time
d) a worldwide layer rich in the element iridium that dates to that time

d) a worldwide layer rich in the element iridium that dates to that time

What do we mean by a primitive meteorite?

a) :a meteorite that was discovered by primitive people
b) a type of meteorite that is made mostly of high-density metals
c) a meteorite that fell to Earth at least 4 billion years ago
d) a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula almost 4.6 billion years ago

d) a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula almost 4.6 billion years ago

What is the main factor that makes Earth more geologically active than the other terrestrial planets?

a) It is farthest from the Sun, so it receives less light.
b) It has a large Moon, so it is heated by tidal forces.
c) It has far more radioactive material than other planets.
d) It formed much later than the other planets.
e) It is larger, so it has retained its internal heat for longer.

e) It is larger, so it has retained its internal heat for longer.

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

A) oxygen in the atmosphere and mantle convection
b) the existence of life and oxygen in the atmosphere
c) Earth's liquid outer core and solid inner core
d) mantle convection and a thin lithosphere

d) mantle convection and a thin lithosphere

Which of the following can act like a long-term "thermostat" that helps keep Earth's average temperature fairly stable?

a) radioactive elements trapped in the Earth's mantle
b) heat stored in the Earth's magnetosphere
c) heat stored in the Earth's liquid core
d) the carbon dioxide cycle that moves carbon dioxide between Earth's atmosphere, oceans, and rock

d) the carbon dioxide cycle that moves carbon dioxide between Earth's atmosphere, oceans, and rock

Rank these planets in order of the strength of the greenhouse effect on the planet, from the weakest to the strongest greenhouse effect.

a) Mars, Mercury, Earth, Venus
b) Mercury, Venus, Earth, Mars
C) Mercury, Earth, Mars, Venus
d) Mars, Earth, Venus, Mercury
e) Mercury, Mars, Earth, Venus

e) Mercury, Mars, Earth, Venus

Where do scientists think that Jupiter's strong magnetic field is generated?

a) in its rocky core
b) in its liquid hydrogen layer
c) in its gaseous hydrogen layer
d) above the cloud tops
e) in its metallic hydrogen layer

e) in its metallic hydrogen layer

Jupiter's colors come in part from its three layers of clouds. Which of the following is not the primary constituent of one of Jupiter's cloud layers?

a) clouds of water
b) clouds of ammonium hydrosulfide
c) clouds of ammonia
d) clouds of sulfuric acid

d) clouds of sulfuric acid

How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth?

a) They are about the same as average winds on Earth.
b) They are slightly faster than average winds on Earth.
c) They are slightly slower than average winds on Earth.
d) They are much faster than hurricane winds on Earth.

d) They are much faster than hurricane winds on Earth.