1) Currently, slow surface evolution on the moon and Mercury is limited to
(A) low density masses of rock rising from the interior, (B) "sandblasting" by micro-meteorite impacts, (C) seismic quakes disrupting the surface features, (D) plate tectonics creating and destroying crustal rocks, (E) all of the above.
Correct: (B) Tiny meteorites, the grains left over from the early stages of the solar nebula, orbit the sun and occasionally collide with planets like Mercury. Though the grains are small, they travel fast (typically 30 km/sec) so leave tiny pits in rocks on the surface (see p. 468 of Seeds). Given time, micro-meteorites wear rocks down to powder (see p. 457).
Incorrect: (A, C, D, & E) Mercury is a small planet that has cooled and (mostly?) solidified inside. Rising and sinking rock, seismic quakes (like Earthquakes), and plate tectonics are all associated with molten (or at least semi-solid "plastic") rock found in larger planets that have retained their heat of formation, like Earth and Venus.
2) The lunar maria are
(A) the lava plains of the lunar lowlands, (B) the smooth plateaus of the lunar highlands, (C) less than one billion years old, (D) moving plates of lunar crust, (E) older than the lunar lowlands.
Correct: (A) They are thought to have formed when large impacts punctured the cooling crust of the moon, allowing darker, denser basalt lava from the still molten mantle to flood the low-lying surface of the moon. See p. 451 and 459.
Incorrect: (B) The moon's highlands are characterized by rugged terrain composed of overlapping impact craters. (C) Radioactive decay measurements of moon rocks returned by Apollo indicate the maria are 3.2 to 3.8 billion years old (see Table 21-1). (D) There is no evidence for plate tectonics (moving plates of surface crust) on the moon (see p. 461). (E) The maria are the lunar lowlands.
3) The presence of breccias among the lunar rock samples shows that
(A) volcanism did not occur on the moon, (B) molten lava once flowed over the lunar surface, (C) the crust must have been made of anorthosite, (D) water once existed on the moon in the form of small lakes and streams, (E) the lunar surface was fragmented by meteorite impacts.
Correct: (E) Breccias are rock fragments (presumably produced by ancient impacts) that were fused together by the heat and pressure of a more recent impact to form a "new" rock.
Incorrect: (A) While it is true that volcanoes do not exist on the moon, breccias are not related to volcanism. (B) Breccias are not related to volcanism (C) The highland crust is made of light-colored, low-density anorthosite rocks that floated to the lunar surface when the moon was molten, and which solidified about 4 billion years ago, during the heavy bombardment era. Anorthosite is a igneous (hardened from lava) rock that is not related to breccias. (D) There is no evidence suggesting that the moon ever had water on its surface (see p. 455-6).
4) Which of the following was not a result of the Apollo missions to the moon?
(A) Close-up pictures of craters, hills and other features on the moon's surface, (B) rock samples from several different places on the moon, (C) samples of the powdery lunar regolith, (D) seismic measurements which led to a rough understanding of the moon's interior structure, (E) fossil evidence of plant and animal life on the moon that is now extinct.
Correct: (E) No evidence has ever been found to indicate the moon has harbored life. Life would be a huge surprise on this airless, waterless world!
Incorrect: (A-D) The Apollo moon landings provided all of these firsthand pieces of evidence (see p.454-5).
5) How many human beings have ever walked on the moon?
(A) 1, (B) 2, (C) 6, (D) 12, (E) lots and lots.
Correct: (D) There were six successful Apollo landings, each carrying two astronauts to the lunar surface (the third astronaut in each mission stayed in the Command Module, orbiting the moon). See pages 454-455.
Note: I don't offer the answer 0 here. You may have heard a "conspiracy theory" rumor, or seen seen the FOX television show suggesting that the moon landings were faked. If you are interested in following up on the arguments the conspiracy theorists present and the responses thoughtful people to them, you can visit a website one of my students created on the topic. Much of the "evidence" the conspiracy theorists cite is just plain silly, while some of it involves a little thought and maybe some scientific background. I find the evidence unconvincing, and in my mind there is no question that the Apollo astronauts visited the moon. I don't know of any astronomers or geologists who believe in the hoax theory either.
6) The lunar highlands were created when
(A) wind scoured the regolith off the underlying light-colored rocks, (B) molten rock from beneath the cooling crust rose to the surface and flooded the lowlands, (C) volcanoes, produced by crustal plates descending and melting, erupted, (D) the moon's surface cooled and solidified while being struck by countless asteroids late in the era of heavy bombardment, (E) uranium in the rocks decayed and melted them.
Correct: (D) The lunar highlands are the original, low-density rocks that was the first rock on the moon to cool and harden from molten lava.
Incorrect: (A) There is no atmosphere on the moon, hence no wind. (B) This was how the maria formed (see Question 2). (C) There is no evidence for volcanoes or plate tectonics on the moon. (E) Uranium and other radioactive elements in the moon's rocks probably played an important role in causing the newly-formed moon to be molten. However, if the rocks had been solid and then were melted by energy released from radioactive decay, they would have tended to flow off the high regions and fill in the lowlands.
7) The large impact hypothesis suggests that the moon formed when proto-Earth was hit by a large planetesimal, and a large amount of material was thrown into orbit. Which of the following ideas does not fit with this hypothesis?
(A) The iron core from the impactor would skip off proto-Earth and form the large iron core we observe in the moon today; (B) Computer simulations tracking gravitational forces on various chunks of mass show that some combinations of impactor size, speed, and angle of impact can throw material into orbit around Earth; (C) If the proto-Earth had differentiated before the impact, the material thrown into space would consist mainly of rocky minerals from the crust and mantle, producing a moon rich in rocky material similar to that of the Earth; (D) The material thrown into space would be hot from the impact, and any "volatile" material like water and carbon dioxide would escape as a gas before the material could form the moon; (E) The iron core of the impactor would merge with the Earth's iron core, leaving the moon with little iron.
Correct: (A) Statements (B-E) are true, while (A) is incorrect. Simulations indicate that gravity would pull the iron core of the impactor (which is dense/massive) strongly toward the earth, where it would sink toward the center (like during differentiation). See the discussion on p. 462-3, look carefully at Figure 21-13, and remember the computer simulation video of the L.I.H. we saw in class.
8) The moon is no longer geologically active because
(A) it rotates too slowly, (B) its radioactive elements have all decayed, (C) it is small and its interior has cooled and solidified, (D) its crust is too thin, (E) it does not have water on its surface.
Correct: (C) Small spheres cool fast. Seismic studies from Apollo indicate the moon is completely (or almost completely) solid inside. Geologic activity like earthquakes, volcanoes and plate tectonics occurs when molten or semi-molten rock under the surface undergoes convection.
9) Mercury experiences very cold nights and very hot days. This is due to
(A) Mercury's slow rotation on its axis, so night and day each last a long time; (B) the very long amount of time it takes for Mercury to orbit the sun; (C) Mercury's lack of atmosphere, so there is no "blanket" to slow the escape of heat during the night; (D) the extreme eccentricity of Mercury's orbit, which takes it very close to and very far from the sun on each orbit, (E) answers A and C.
Correct: (E) Mercury's long days result in the sun heating the surface rocks to high temperatures, and the long nights allow plenty of time for the rocks to radiate away their heat (in the form of infrared light) and cool off. Atmospheres like those found on Earth and Venus tend to trap in the heat at night (especially if they contain lots of carbon dioxide, to maintain the greenhouse effect). Since Mercury has no atmosphere, the surface rocks cool off during the long nights and reach low temperatures (see p. 465).
10) The theory that Mercury's large iron core shrank slightly when it cooled long ago has been proposed to explain Mercury's
(A) light-colored lava plains, (B) large craters, (C) weak magnetic field, (D) lobate scarps, (E) Caloris Basin.
Correct: (D) Lobate scarps are the long, curving cliffs unique to Mercury (see p. 466 and Figure 21-17), and are thought to be "faults" where regions of rock collapsed as the iron core shrank beneath them.
11) Mercury's large iron/nickel core is deduced from which of the following observations?
(A) Mercury's uncompressed average density of 5.4 gm/cm3 is large compared to the other terrestrial planets, (B) Careful seismic observations by the many spacecraft that have landed on Mercury's surface, (C) The high abundance of iron in rocks that have been returned from Mercury's lowland plains, (D) The dark-colored lava flows in Mercury's lowlands indicate an abundance of iron-rich minerals right below the surface, (E) answers C and D.
Correct: (A) The uncompressed density (density after correcting for the compressing effect of gravity) of the Earth, Venus and Mars are all about 4 gm/cm3 (see Table 19-2). Most rocks have densities less than 4 gm/cm3 (remember our density measurements in class?), so a denser material is needed to account for Mercury's high average density. Iron has a density around 8 gm/cm3 and is relatively common in the solar system (for example, Earth's core). A disproportionately large iron core would account for Mercury's high average density.
12) The features that are most common on the surface of Mercury are
(A) a maze of lobate scarps, (B) pancake domes, (C) impact craters, (D) shield volcanoes, (E) long ranges of mountains running parallel to trenches, indicative of plate tectonics.
Correct: (C) Though there are lobate scarps on Mercury, there are many more craters (for example, in Figure 21-17 there are many craters and only one lobate scarp). Pancake domes, shield volcanoes and plate tectonics are found on larger, more geologically active worlds like Venus, Mars, and Earth.
13) Observations by Mariner 10 show that Mercury has a magnetic field 200 times weaker than Earth's. Why is this surprising?
(A) Mercury's density suggests its core is like Earth's, therefore its magnetic field should be of nearly equal strength; (B) Mercury is hot enough that its core should be very molten and produce a magnetic field much stronger than Earth's; (C) Mercury's small size suggests that its core should have cooled and solidified, so no magnetic field is expected; (D) Mercury's fast rotation suggests it should have a very strong magnetic field; (E) Mercury is so close to the sun that its magnetic field should be destroyed by the solar wind.
Correct: (C) Magnetic fields are created by convection and rotation stirring a fluid that conducts electricity. In the sun, the fluid is hot plasma (ionized gas). In terrestrial planets like the Earth and Mercury, the fluid is liquid iron in the core. Given Mercury's small size, it is surprising that Mercury has retained enough heat to still have a liquid (or partially liquid) iron core.
14) The surface of Venus has been studied using
(A) radar maps made from satellites orbiting Venus, (B) pictures obtained in visible light from telescopes on Earth as well as satellites orbiting Venus, (C) robotic spacecraft that have landed on Venus, (D) manned spacecraft that have landed on Venus, (E) answers A and C.
Correct: (E) Venus's thick clouds make it impossible to view the surface rocks from Earth or space, but radar is not affected by the clouds and provides detailed maps of the surface (for example, Figures 22-3, 22-5 to 22-10). Also, several Soviet spacecraft have landed on the surface and taken pictures (Figure 22-2). No spacecraft with a human crew have traveled to Venus (or any planet beyond Earth's moon) yet.
15) The geology of Venus appears to be affected the most by
(A) volcanism, (B) plate tectonics, (C) erosion by flowing water, (D) impact cratering, (E) micro-meteorites.
Correct: (A) There are many volcanoes, lava flows, coronae and pancake domes on Venus. There is no liquid water on Venus. Venus's atmosphere is so thick that an micro-meteorites burn up in the atmosphere, and only occasionally do larger meteoroids survive to create impact craters on the surface.
16) The greenhouse effect keeps Venus hot because
(A) the atmosphere contains free oxygen, (B) the atmosphere is rich in carbon dioxide, (C) the surface converts infrared to visible radiation, (D) the clouds of acid vapors reflect away most of the sunlight falling on Venus, (E) the magnetic field traps large numbers of particles from the solar wind.
Correct: (B) Carbon dioxide (CO2) reflects infrared light trying to escape the surface back onto the surface, keeping it hot (see p. 443-4).
17) Two containers hold equal masses of hydrogen gas (H2). A thermometer in container A reads a temperature of 20 degrees, while a thermometer in container B reads 80 degrees. The gas particles in container A
(A) are moving more slowly than those in container B, (B) are moving faster than those in container B,(C) have a larger electric charge than those in container B, (D) have a stronger gravitational pull than those in container B, (E) have a weaker gravitational pull than those in container B.
Correct: (A) Temperature measures the motion of the particles -- lower temperatures correspond to slower motions (remember that all atomic and molecular motion stops at 0°K, absolute zero).
18) Coronae on Venus are believed to be
(A) impact craters, (B) caused by rising convection currents in the interior of Venus, (C) the results of plate tectonics, (D) located only in the polar regions of Venus, (E) older than the highlands such as Ishtar Terra.
Correct: (B) Coronae are bulges in the crust caused when magma rose from inside the planet (see p. 479 and Figure 22-8).
19) Shield volcanoes
(A) are produced by thick, viscous lava, (B) are found only on Earth, (C) have steeply sloping sides, (D) are found in Hawaii and Venus, among other places, (E) are extinct composite volcanoes that have been worn down by erosion.
Correct: (D) The "volcanoes" centerfold on p.480-1 discusses shield volcanoes on Mars (Olympus Mons), Venus (Gula Mons and Sif Mons), and Earth (Hawaiian Islands).
Incorrect: (A) and (C) are characteristics of composite volcanoes, commonly found on Earth near seafloor trenches where seafloor plates are being pushed under continental crust and melting. Common examples are the volcanoes in Washington and Oregon states, the Andes in South America, and volcanoes in Japan and the Pacific Islands.
20) The high temperatures on the surface of Venus result from a "chain" of related causes. Which of the following statements is not part of this chain?
(A) Venus has no ozone layer, so ultraviolet rays from the sun have destroyed much of Venus's water, (B) with no liquid oceans, Venus had no way to "lock away" its atmospheric CO2 as limestone,(C) much of the water on Venus is "locked away" as ice at the bottom of polar craters,(D) the CO2 in Venus's atmosphere traps in infrared radiation, so the surface temperature rises,(E) Venus is closer to the sun than Earth, so is warm enough that its water never condensed to form oceans.
Correct: (C) is the statement that is not part of the chain of causes. Venus's thick atmosphere distributes heat to the poles and night side of Venus very efficiently, so they are all too hot for liquid (let along frozen) water to exist. If you thought water ice exists in the polar craters, you are probably remembering Mercury. Though Mercury is close to the sun and very hot on the daytime side, there is no atmosphere to trap in heat and distribute it around the planet (by winds), so places that don't receive direct sunlight can be very cold. Astronomers think there may be frozen water ice at the bottoms of craters near Mercury's poles, where the sun never shines.