Astronomy 1002
Homework #3


1. Why is the Earth is a differentiated body

  1. denser materials formed near the core
  2. denser objects rise toward the surface
  3. the core has a high temperature
  4. the core has a high pressure
  5. gravity pulls denser materials toward the core


2. What is the major source of the Earth's interior heat?

  1. the high pressures of the overlying material.
  2. the high densities at the Earth's center.
  3. tidal friction caused by the Moon.
  4. decay of radioactive elements
  5. solar energy, which heated the material when it was forming the Earth


3. The Earth's magnetic field is thought to be caused by a combination of convection in a molten core and

  1. rotation.
  2. charged particles from space falling on the Earth.
  3. lunar tidal effects.
  4. the Sun's strong gravitational pull on the Earth's equatorial bulge.


4. What causes the aurora borealis?

  1. electrical storms near the Earth's surface
  2. electrical storms near the top of the Earth's atmosphere
  3. by the Moon's tidal effects on the Earth's atmosphere
  4. solar particles interacting with the Earth's magnetic field and atmosphere
  5. unknown electrical effects associated with the subduction zones between continental plates


5. What statement about the greenhouse effect is true?

  1. It causes planets to be green.
  2. It helps cool the Earth and keep it from becoming much warmer than it is.
  3. It is produced by the small amount of ozone in the atmosphere.
  4. It balances out the effects of the ozone hole.
  5. It comes about when solar energy cannot escape the Earth's atmosphere.


6. The Earth's primitive atmosphere probably consisted of substantial amounts of

  1. hydrogen.
  2. methane.
  3. ammonia.
  4. oxygen.
  5. carbon dioxide


7. If the average density of the Earth is 5.5 grams per cubic centimeter but the density of a typical rock you pick up is 3 grams per cubic centimeter, what is the most reasonable conclusion?

  1. The Earth is differentiated.
  2. There is an error in the statement.
  3. The Earth's density changes with the inverse square of the distance from the center.
  4. The Earth's surface consists of large amounts of iron.
  5. The Earth's interior is mostly molten.


8. The maria regions on the Moon turn out to be about _____ years old, whereas the highlands appear to be _____ .(choose best answer)

  1. 3.5 billion; a billion years older
  2. 3.5 billion; a billion years younger
  3. 1 billion; about the same
  4. 1 billion; younger
  5. 1 billion; older


9. What are most lunar craters caused by?

  1. volcano-like activity on the Moon.
  2. a local collapse of the surface into subsurface caverns.
  3. equal number of volcanic and impact events.
  4. crustal movements similar to continental drift.
  5. impact events from meteoric material.


10. Why are the lunar mare smooth?

  1. because of continental motions over billions of years
  2. because of erosion from a primitive lunar atmosphere
  3. because of past lava flows
  4. because of erosion from a primitive lunar ocean
  5. because of the strong tidal effects Earth exerts on the Moon


11. If you lived on the far side of the Moon, how often would you see the Earth?

  1. once every 29.5 days
  2. once every 27.3 days
  3. once every 24 hours
  4. never
  5. There is not enough information to answer the question.


12. Fact: the Earth and the Moon have nearly identical relative abundances of the various oxygen isotopes. What can we conclude from this fact?

  1. The relative abundances of oxygen isotopes are the same all over the universe.
  2. The Moon was probably formed elsewhere and then captured.
  3. The Moon formed in the same way and at the same time as the Earth.
  4. The Moon and the Earth formed from the same material.
  5. The Moon formed by fission from the forming Earth.


13. What is the primary chemical constituent of the present day atmosphere of Mars?

  1. carbon dioxide
  2. carbon dioxide and nitrogen
  3. hydrogen, helium, methane, ammonia, nitrogen, and neon
  4. nitrogen and oxygen


14. What statement concerning volcanoes on Mars is true?

  1. They are larger than those on Earth.
  2. They indicate that the core of Mars is much larger than the Earth's.
  3. They are probably due to meteoric impact.
  4. They are the source of oxygen in Mars' atmosphere.
  5. They may actually just be mountains.

15. What does the presence of a planetary magnetic field suggest about its structure? (Choose best answer)

  1. Its core is probably composed of solid iron.
  2. It has a rocky surface, with magnetism locked up in rocks as iron oxides.
  3. It probably has a molten iron core, and the rotation of the planet generates the field.
  4. The planet has been magnetized in the past by some passing object.
  5. The planet has been disrupted at some time, so that material from its magnetic interior has gotten out.


16. Why is the Earth's atmosphere so different from that of the other terrestrial planets?

  1. Planetary atmospheres are entirely due to materials outgassed from the interior, so the Earth must have just erupted different elements.
  2. The Earth is less massive, so the other elements seen elsewhere are not on Earth because they escaped from its weak gravity.
  3. On the Earth, water dissolved the carbon dioxide and plants made oxygen.
  4. Mars and Venus have more iron, and this plus oxygen made rust.
  5. We haven't got a clue.


17. What is the primary reason why Mercury is difficult to see from the Earth?

  1. It is a very small planet.
  2. It is very faint.
  3. It rotates very slowly.
  4. It always appears near the bright Sun.
  5. Its orbit is highly elliptical.


18. Which of the following observations of Mars indicates the presence of annual seasons?

  1. Plant growth has been detected in the springtime.
  2. In each hemisphere, the polar cap changes in size as Mars orbits the Sun.
  3. Volcanism shows a seasonal dependence.
  4. Seasonal floods have been detected.


19. What is the evidence for high winds on Mars?

  1. The Martian probes photographed rippled sand dunes.
  2. Theory predicts it.
  3. The slow rotation implies one side is strongly heated, and the temperature difference drives strong winds.
  4. Being farther from the Sun and thus colder, there must be winter blizzards with strong winds.


20. Which surface feature has been discovered on both Mercury and Mars?

  1. maria
  2. large volcanoes
  3. river beds
  4. large wrinkled ridges
  5. craters


21. Which planet's rotational characteristics differs most substantially from that of all the other terrestrial planets?

  1. Earth
  2. Mercury
  3. Mars
  4. Venus


22. Venus's clouds are observed to contain substantial amounts of

  1. water vapor.
  2. sulfuric acid.
  3. carbon monoxide.
  4. nitrogen.
  5. methane.


23. Why is Mars red?

  1. Its surface rocks are highly radioactive.
  2. Because of the way sunlight refracts through the Martian atmosphere.
  3. Because of dust lifted into the atmosphere by Mar's high winds.
  4. Its distance from the Sun keeps it cool and therefore red.
  5. Iron oxide on the surface


24. Why does the Earth's atmosphere have a higher fraction of carbon dioxide than the atmosphere of Mars?

  1. It formed that way.
  2. Earth's volcanoes have emitted large amounts of carbon dioxide.
  3. Earth's high escape velocity has held onto its carbon dioxide.
  4. Animals on Earth give off carbon dioxide.
  5. The statement is wrong; Mars has more atmospheric carbon dioxide.


25. The temperature at Mercury's north and south poles are expected to be

  1. about the same as at the equator.
  2. greater than at the equator.
  3. less than at the equator.


26. Which of the following observations provide evidence that Mars had substantial water in the past?

  1. channels that meander over the surface
  2. small pools of water today indicate more water in the past
  3. large amounts of water vapor in the atmosphere
  4. Mars's satellites, which consist primarily of water ice
  5. Viking spacecraft observations of high soil moisture

27. Why do astronomers think that Venus lacks the small craters observed on other terrestrial planets?

  1. all the small impacting bodies had fallen into the Sun in earlier times.
  2. space contains only large impacting bodies and no small ones.
  3. small bodies burned up while entering the planet's atmosphere.
  4. Venus's magnetic field shielded the planet from impact from small bodies.
  5. both C and D contribute to the low number of small craters.


28. What evidence is there for active volcanism on Venus?

  1. direct observation of eruption with telescopes from Earth
  2. direct observation of eruption with orbiting spacecraft
  3. direct observation of eruption by landers on the surface
  4. variable amounts of sulfur dioxide in the atmosphere
  5. radioactivity on the surface around certain mountains that look volcanic


29. What is thought to have caused Mercury's cliffs?

  1. compression and shrinking during the crust's cooling
  2. extremely large seismic events, which cracked open the hard surface
  3. extensive lava flows early in the planet's history when the crust was still soft
  4. the motion of continental plates
  5. large impact events


30. Why is Venus' lack of a magnetic field not too surprising?

  1. Venus has a slow rotation period.
  2. Venus shows retrograde rotation.
  3. Venus lacks active volcanism.
  4. Venus has a radioactive surface.
  5. Venus has a high escape velocity.


31. Which planet has the largest fraction of its volume located in its core?

  1. Mars
  2. Venus
  3. Earth
  4. Mercury
  5. none of the above


32. Which terrestrial planet, in addition to Earth, has a substantial amount of lightning activity in its atmosphere?

  1. Mars
  2. Venus
  3. Mercury
  4. None other than Earth show observable lightning.


33. Which of the following is a piece of evidence that Venus is not subject to strong erosional processes?

  1. Venus's atmosphere is nearly constant and unchanging.
  2. Fault regions do not appear eroded.
  3. Radar observations show its volcanoes to show sharp peaks.
  4. Its surface rocks have sharp edges.


34. What is Olympus Mons?

  1. a giant shield volcano on Mars
  2. the tallest mountain on Mercury
  3. one of Mars's moons
  4. a mountain on Venus that is higher than Mt. Everest
  5. a volcano discovered on Mercury


35. Which one of the following surface features is found on all terrestrial planets and the Moon?

  1. maria
  2. large volcanoes
  3. river beds
  4. large wrinkled ridges
  5. craters