Midterm #2
Astronomy 100 – Prof. Vahé Peroomian
Summer Session 2016 – June 9, 2016
Each of the 50 questions is worth 2 points. Please use the Scantron for your answers.
These sheets will NOT be graded.
1) Rank the five terrestrial worlds in order of size from smallest to largest.
A) Mercury, Venus, Earth, Moon, Mars
B) Mercury, Moon, Venus, Earth, Mars
C) Moon, Mercury, Venus, Earth, Mars
D) Moon, Mercury, Mars, Venus, Earth
E) Mercury, Moon, Mars, Earth, Venus
2) Why does Earth have the strongest magnetic field among the terrestrial worlds?
A) It is the only one that has a metallic core.
B) It rotates much faster than any other terrestrial world.
C) It is the only one that has both a partially molten metallic core and reasonably rapid rotation.
D) It is by far the largest terrestrial world.
E) It is the most volcanically active world.
3) Which of the following does not have a major effect in shaping planetary surfaces?
A) impact cratering
B) volcanism
C) tectonics
D) erosion
E) magnetism
4) The terrestrial planet cores contain mostly metal because
A) the entire planets are made mostly of metal.
B) metals condensed first in the solar nebula and the rocks then accreted around them.
C) metals sank to the center during a time when the interiors were molten throughout.
D) radioactivity created metals in the core from the decay of uranium.
E) convection carried the metals to the core.
5) What is the most abundant gas in Titan's atmosphere?
A) methane
B) nitrogen
C) hydrogen compounds
D) oxygen
E) argon
6) What kind of surface features may result from tectonics?
A) mountains
B) valleys
C) volcanos
D) cliffs
E) all of the above
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7) 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.
8) What is the Cassini division of Saturn's rings?
A) a dark ring, visible from Earth, composed of dark, dusty particles
B) a large gap, visible from Earth, produced by an orbital resonance with the moon Mimas
C) the imaginary circle marking the halfway point of Saturn's rings
D) the widest ring of Saturn, located between two large ring gaps
E) the most opaque ring of Saturn, made of highly reflective ice particles
9) Under what circumstances can differentiation occur in a planet?
A) The planet must have a rocky surface.
B) The planet must be made of both metal and rock.
C) The planet must have an atmosphere.
D) The planet must be geologically active, that is, have volcanoes, planetquakes, and erosion
from weather.
E) The planet must have a molten interior.
10) Why is Saturn almost as big as Jupiter, despite its smaller mass?
A) Jupiter's greater mass compresses it more and increases its density.
B) Saturn's rings make the planet look bigger.
C) Saturn is further from the Sun, thus cooler, and therefore less compact.
D) Saturn has a larger proportion of hydrogen and helium than Jupiter, and is therefore less
dense.
E) Jupiter's strong magnetic field constrains its size.
11) 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
A) erosion destroyed the smaller craters that formed on the basin.
B) Mercury's atmosphere prevented smaller objects from hitting the surface.
C) only very large impactors hit Mercury's surface in the past.
D) the Caloris Basin formed toward the end of the solar system's period of heavy bombardment.
E) the Caloris Basin was formed by a volcano.
12) What is Charon?
A) Pluto's largest moon
B) the largest known asteroid
C) the largest known comet
D) one of the Galilean moons of Jupiter
E) a moon of Neptune
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13) A planet is most likely to have tectonic activity if it has
A) low surface gravity.
B) high surface gravity.
C) low internal temperature.
D) high internal temperature.
E) a dense atmosphere.
14) Why is Mars red?
A) It is made primarily of red clay.
B) Its surface rocks were rusted by oxygen.
C) Its atmosphere scatters blue light more effectively than red light.
D) Its surface is made of ices that absorb blue light.
E) Its surface is made of ices that absorb red light.
15) The three principal sources of the internal heat of terrestrial planets are
A) conduction, differentiation, and accretion.
B) accretion, differentiation, and radioactivity.
C) accretion, differentiation, and eruption.
D) convection, differentiation, and eruption.
E) conduction, convection, and eruption.
16) Valles Marineris is a(n)
A) large valley on the Moon.
B) extensive plain on Mars.
C) huge series of cliffs on Mercury.
D) large canyon on Mars.
E) large canyon on Venus.
17) Suppose Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature
would be
A) –16°C, which is well below freezing.
B) 0°C, or about the freezing point for water.
C) 10°C or about 5°C cooler than it is now.
D) 15°C, or about the same as it is now.
E) 20°C, or about 5°C warmer than it is now.
18) Why does Mars have more extreme seasons than Earth?
A) because it is farther from the Sun
B) because it has a larger axis tilt
C) because it has a more eccentric orbit
D) because it has more carbon dioxide in its atmosphere
E) all of the above
19) The footprints left on the moon by the Apollo astronauts will likely last for
A) no time; they were quickly erased by micrometeorites.
B) a few decades.
C) millions of years.
D) one billion years
E) the remaining existence of the Moon.
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20) If the Earth were to warm up a bit, what would happen?
A) Carbonate materials would form in the oceans more rapidly, the atmospheric CO2 content
would decrease, and the greenhouse effect would weaken.
B) Carbonate materials would form in the oceans more slowly, the atmospheric CO2 content
would increase, and the greenhouse effect would strengthen.
C) Carbonate materials would form in the oceans more rapidly, the atmospheric CO2 content
would decrease, and the greenhouse effect would strengthen.
D) There would be a runaway greenhouse effect, with the Earth becoming ever hotter until the
oceans evaporated (as may have happened on Venus).
E) The ice caps would melt and cool the Earth back to its normal temperature.
21) The Sun is gradually increasing in luminosity as it ages. It is 20% more luminous than it was
when it was born. Why isn't this considered to be an explanation for global warming?
A) The Sun is increasing in luminosity much too slowly, over many millions of years.
B) The scientists are covering up this potentially valid explanation.
C) The amount of energy the Earth receives from the Sun remains constant regardless of what
the Sun does.
D) What the Sun was doing millions of years ago is what determines Earth's temperature, since
the Earth doesn't respond directly to what the Sun is doing today.
22) Why is the sky blue (on Earth)?
A) because the Sun emits mostly blue light
B) because molecules scatter blue light more effectively than red light
C) because molecules scatter red light more effectively than blue light
D) because deep space is blue in color
E) No one knows—this is one of the great mysteries of science.
23) What mechanism is most responsible for generating the internal heat of Io that drives its volcanic
activity?
A) accretion
B) radioactive decay
C) differentiation
D) tidal heating
E) bombardment
24) How thick are Saturn's rings from top to bottom?
A) a few million kilometers
B) a few tens of thousands of kilometers
C) a few hundred kilometers
D) a few kilometers
E) a few tens of meters
25) Overall, Jupiter's composition is most like that of ________.
A) the Sun
B) Earth
C) a comet
D) an asteroid
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Use the following choices for questions 26 - 30 .
A. Ganymede
B. Triton
C. Europa
D. Titan
E. Io
26.
27.
28.
29.
30.
_____________ is the most volcanically active body in the solar system
_____________ is thought to have a deep, subsurface ocean of liquid water
_____________ is probably a captured Kuiper Belt object
_____________ is the target of the Huygens probe, which landed on its surface.
_____________ is the largest moon in the solar system
31) How do the jovian planet interiors differ?
A) All have cores of about the same mass, but differ in the amount of surrounding hydrogen and
helium.
B) The core mass decreases with the mass of the planet.
C) The composition changes from mostly ammonia in Jupiter and Saturn to mostly methane in
Uranus and Neptune.
D) The composition changes from mostly hydrogen in Jupiter and Saturn to mostly helium in
Uranus and Neptune.
E) All have about the same amount of hydrogen and helium but the proportion of rocks is greater
in those planets closer to the Sun.
32) Which planet could an astronaut visit without the need for a spacesuit (and survive)?
A) Mercury
B) Venus
C) the Moon
D) Mars
E) None; an astronaut would need a spacesuit to survive a visit to any other planet in the solar
system.
33) Where did the elements heavier than hydrogen and helium come from?
A) They were produced in the Big Bang.
B) They evolved from hydrogen and helium shortly after the Big Bang.
C) They were produced inside stars.
D) They were produced inside dense interstellar gas.
E) All of the above
34) The region of our solar system between Mercury and Mars has very few asteroids, while the
region between Mars and Jupiter has many asteroids. Based on what you have learned, what is
the most likely explanation for the lack of asteroids between Mercury and Mars?
A) There were very few planetary leftovers in this region because most of the solid material was
accreted by the terrestrial planets as the planets formed.
B) It was too hot for asteroids to form in this part of the solar system.
C) Gravity was too weak to allow asteroids to form in this part of the solar system.
D) All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt
between Mars and Jupiter.
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35) Which of the following best describes why we think the terrestrial planets formed in the inner
solar system and the jovian planets formed in the outer solar system?
A) The jovian planets were made largely from gas, and nearly all the gas from which our solar
system formed was in the outer solar system, not the inner solar system.
B) The large jovian planets occupy much more space than the small terrestrial planets, so they
can exist only in places like the outer solar system, where there is a lot more space available
than in the inner solar system.
C) The terrestrial planets grew from "seeds" of metal and rock, and these materials could
condense only in the inner solar system.
D) The terrestrial planets grew from "seeds" of metal and rock, whereas the jovian planets grew
from seeds that also contained large amounts of hydrogen compounds that condensed only in
the cold outer solar system.
36) What percentage of the mass of the solar nebula consisted of elements other than hydrogen and
helium?
A) 0 percent
B) 0.1 percent
C) 2 percent
D) 20 percent
E) 80 percent
37) Based on our current theory of Earth's formation, the water we drink comes from
A) ice that condensed in the solar nebula in the region where Earth formed.
B) chemical reactions that occurred in Earth's crust after Earth formed.
C) chemical reactions that occurred in Earth's core after Earth formed.
D) material left behind during the giant impact that formed the Moon.
E) comets that impacted Earth.
38) The nebular theory of the formation of the solar system successfully predicts all but one of the
following. Which one does the theory not predict?
A) Planets orbit around the Sun in nearly circular orbits in a flattened disk.
B) the equal number of terrestrial and jovian planets
C) the compositional differences between the terrestrial and jovian planets
D) the presence of asteroids and comets
E) the craters on the Moon
39) Which moons are sometimes called the Galilean moons?
A) the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto
B) the two largest moons in the solar system: Ganymede and Titan
C) the moons that orbit their planet "backward" compared to their planet's rotation, such as
Neptune's moon Triton
D) the moons orbiting Uranus, which was once named "planet Galileo"
40) Which of the following statements about the recently-discovered object Eris is not true?
A) It is thought to be the first example of a new class of object.
B) It is slightly larger than Pluto.
C) It lies well beyond Pluto and Neptune.
D) It orbits the Sun in the same direction as the other planets.
E) It has a moon called Dysomnia
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41) Refer to the above diagram. You find a rock containing radioactive potassium-40 and its decay
product argon-40. You assume that all the argon-40 was made from radioactive decay of
potassium-40. The rock now has twice as much argon-40 as potassium-40; that is, 2/3 of the
original potassium-40 has decayed into argon-40 while 1/3 remains in the rock. Based on this
graph, about how old is the rock?
A) 1.25 billion years
B) 2 billion years
C) 2.5 billion years
D) 3 billion years
E) 3.75 billion years
42) Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains
why?
A) Temperatures on Jupiter and Saturn are too high for methane to condense.
B) Jupiter and Saturn do not contain any methane gas.
C) The rapid rotation of Jupiter and Saturn prevents methane clouds from forming.
D) The stronger gravity on Jupiter and Saturn pulls methane downward so that it can't form
43) On average, how fast do the plates move on the Earth?
A) about 100 meters per year
B) a few centimeters per year
C) about 1 mile per hour
D) a few millimeters per century
E) a few kilometers per year
44) The asteroid belt is located _________.
A) between the orbits of Earth and Mars
B) beyond the orbit of Neptune
C) between the orbits of Jupiter and Saturn
D) between the orbits of Mars and Jupiter
E) between the orbits of Venus and Earth
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45) What would happen to Jupiter if we could somehow double its mass?
A) Its density would decrease and its diameter would double.
B) Its density would stay about the same and its volume would double.
C) It would become a star, with nuclear fusion in its core.
D) Its density would increase but its diameter would barely change.
E) It would become a brown dwarf, with deuterium fusion in its core.
46) Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?
A) Io's gravity allows this region to capture huge numbers of charged particles from the solar
wind.
B) Jupiter's strong magnetic field makes the radiation intense everywhere, and the region around
Io is no different than any other region.
C) The region is full of gases that become ionized after they are released from volcanoes on Io.
D) An orbital resonance between Io, Europa, and Ganymede makes the radiation intense.
47) Which of the following statements about the greenhouse effect is true?
A) Without the naturally occurring greenhouse effect, Earth would be too cold to have liquid
oceans.
B) A weak greenhouse effect operates on Mars.
C) The burning of fossil fuels increases the greenhouse effect on Earth because of the release of
carbon dioxide.
D) One result of an increased greenhouse effect on Earth may be an increased number of severe
storms.
E) All of the above are true.
48) Who was known as the Cartographer of Mars?
A) Percival Lowell
B) Giovanni Schiaparelli
C) Orson Welles
D) H. G. Wells
E) The U.S. Geological Survey
49) Which of the following is not evidence for the existence of water on the Martian surface in the
past or today?
A) Recurring slope linea
B) Glacial flows on the Hellas plain
C) Hematite “blueberries” and “popcorn”
D) The sublimation of the Martian polar caps
E) Potassium deposits at the mouths of flow channels
50) What is orbital resonance?
A) The periodic gravitational interaction of two orbiting bodies on one-another resulting in
changes in the two bodies’ orbits.
B) The heating of a moon’s interior because of tidal forces by the planet it’s orbiting.
C) The breaking down of small moons to create rings around the giant planets.
D) The use of a planet’s gravity to alter the trajectory of a spacecraft and place it in orbit about
the planet.
E) None of the above.
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