Astro All Answers
18) How does the data from ALMA provide direct evidence for nebular theory?
A) It shows concentric gaps in the disk which are almost certainly regions being cleared as planets form.
B) We can see large planets forming.
C) The amount of energy being radiated by the star system indicates there must be planets present.
D) Data from ALMA does not support nebular theory, instead it is causing scientists to revise the theory.
Answer: A
The Cosmic Perspective, 8e (Bennett)
Chapter 9 Planetary Geology: Earth and the Other Terrestrial Worlds
9.1 Multiple-Choice Questions
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
Answer: D
2) What is differentiation in planetary geology?
A) the process by which gravity separates materials according to density
B) the process by which different types of minerals form a conglomerate rock
C) any process by which a planet's surface evolves differently from another planet's surface
D) any process by which one part of a planet's surface evolves differently from another part of the same planet's surface
E) any process by which a planet evolves differently from its moons
Answer: A
3) 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.
Answer: E
4) When we say that a liquid has a high viscosity, we mean that it
A) is runny like water.
B) flows slowly like honey.
C) is very dark in color.
D) is very light in color.
E) conducts electricity.
Answer: B
5) The core, mantle, and crust of a planet are defined by differences in their
A) geological activity.
B) temperature.
C) strength.
D) composition.
E) color.
Answer: D
6) The lithosphere of a planet is the layer that consists of
A) material above the crust.
B) material between the crust and the mantle.
C) the rigid rocky material of the crust and uppermost portion of the mantle.
D) the softer rocky material of the mantle.
E) the lava that comes out of volcanoes.
Answer: C
7) What is the most important factor that determines the thickness, and therefore strength, of the lithosphere?
A) pressure
B) viscosity
C) composition
D) internal temperature
E) distance of planet from Sun
Answer: D
8) 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.
Answer: C
9) Which internal energy source produces heat by converting gravitational potential energy into thermal energy?
A) accretion
B) differentiation
C) radioactivity
D) both A and B
E) all of the above
Answer: D
10) Which internal energy source is the most important in continuing to heat the terrestrial planets today?
A) accretion
B) differentiation
C) radioactivity
D) tidal heating
E) all of the above
Answer: C
11) Which of the following best describes convection?
A) It is the process by which rocks sink in water.
B) It is the process in which warm material expands and rises while cool material contracts and falls.
C) It is the process in which warm material gets even warmer and cool material gets even cooler.
D) It is the process in which a liquid separates according to density, such as oil and water separating in a jar.
E) It is the process in which bubbles of gas move upward through a liquid of the same temperature.
Answer: B
12) What are the circumstances under which convection can occur in a substance?
A) when the substance is subjected to a strong magnetic field
B) when dense material is being added to the substance
C) when the substance is strongly shaken or disturbed by a strong wind
D) when the substance is strongly cooled from underneath
E) when the substance is strongly heated from underneath
Answer: E
13) The three principal sources of 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.
Answer: B
14) The main process by which heat flows upward through the lithosphere is
A) conduction.
B) convection.
C) radiation.
D) accretion.
E) differentiation.
Answer: A
15) 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
Answer: A
16) Which of the following worlds have the thinnest lithospheres?
A) Earth and the Moon
B) Venus and the Moon
C) Mercury and Venus
D) Earth and Mars
E) Earth and Venus
Answer: E
17) Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones?
A) They were cooler when they formed.
B) The smaller ones are farther from the Sun.
C) They have relatively fewer radioactive elements.
D) They have relatively more surface area compared to their volumes.
E) They had more volcanic eruptions in the past, which released their internal heat.
Answer: D
18) Which of the terrestrial worlds has the strongest magnetic field?
A) Mars
B) Earth
C) the Moon
D) Venus
E) Mercury
Answer: B
19) 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.
Answer: C
20) Which of the following most likely explains why Venus does not have a strong magnetic field?
A) It does not have a metallic core.
B) Its rotation is too slow.
C) It is too close to the Sun.
D) It is too large.
E) It has too thick an atmosphere.
Answer: B
21) What are the conditions necessary for a terrestrial planet to have a strong magnetic field?
A) a molten metallic core only
B) fast rotation only
C) a rocky mantle only
D) both a molten metallic core and reasonably fast rotation
E) both a metal core and a rocky mantle
Answer: D
22) Which of the following has virtually no effect on the structure of a planet?
A) its composition
B) its size
C) its magnetic field
D) its mass
Answer: C
23) Which two properties are most important in determining the surface temperature of a planet?
A) composition and distance from the Sun
B) size and chemical composition
C) size and atmosphere
D) internal temperature and atmosphere
E) distance from the Sun and atmosphere
Answer: E
24) 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
Answer: E
25) How large is an impact crater compared to the size of the impactor?
A) the same size
B) 10-20 percent larger
C) 10 times larger
D) 100 times larger
E) 1,000 times larger
Answer: C
26) The relatively few craters that we see within the lunar maria
A) were formed by impacts that occurred before those that formed most of the craters in the lunar highlands.
B) were formed by impacts that occurred after those that formed most of the craters in the lunar highlands.
C) were created by the same large impactor that led to the formation of the maria.
D) are volcanic in origin, rather than from impacts.
E) are sinkholes that formed when sections of the maria collapsed.
Answer: B
27) When we see a region of a planet that is not as heavily cratered as other regions, we conclude that
A) there is little volcanic activity to create craters.
B) the planet is rotating very slowly and only one side was hit by impactors.
C) the planet formed after the age of bombardment and missed out on getting hit by leftover planetesimals.
D) the surface in the region is older than the surface in more heavily cratered regions.
E) the surface in the region is younger than the surface in more heavily cratered regions.
Answer: E
28) Volcanism is more likely on a planet that
A) is closer to the Sun.
B) is struck often by meteors and solar system debris.
C) has high internal temperatures.
D) doesn't have an atmosphere or oceans.
Answer: C
29) Shallow-sloped shield volcanoes are made from lava that
A) is as runny as liquid water.
B) has a medium viscosity.
C) has a high viscosity.
D) can have any viscosity.
Answer: B
30) Steep-sided stratovolcanoes are made from lava that
A) is as runny as liquid water.
B) has a medium viscosity.
C) has a high viscosity.
D) can have any viscosity.
Answer: C
31) What type of stresses broke Earth's lithosphere into plates?
A) impacts of asteroids and planetesimals
B) internal temperature changes that caused the crust to expand and stretch
C) the circulation of convection cells in the mantle, which dragged against the lithosphere
D) cooling and contracting of the planet's interior, which caused the mantle and lithosphere to be compressed
E) volcanism, which produced heavy volcanoes that bent and cracked the lithosphere
Answer: C
32) Which of the following describes tectonics?
A) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
B) the eruption of molten rock from a planet's interior to its surface
C) the disruption of a planet's surface by internal stresses
D) the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
Answer: C
33) Which of the following describes erosion?
A) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
B) the eruption of molten rock from a planet's interior to its surface
C) the disruption of a planet's surface by internal stresses
D) the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
Answer: D
34) Which of the following describes volcanism?
A) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
B) the eruption of molten rock from a planet's interior to its surface
C) the disruption of a planet's surface by internal stresses
D) the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
Answer: B
35) Which of the following describes impact cratering?
A) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
B) the eruption of molten rock from a planet's interior to its surface
C) the disruption of a planet's surface by internal stresses
D) the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
Answer: A
36) 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.
Answer: D
37) What kind of surface features may result from tectonics?
A) mountains
B) valleys
C) volcanos
D) cliffs
E) all of the above
Answer: E
38) What is basalt?
A) any substance that evaporates easily and is a gas, liquid, or ice on Earth
B) a type of rock that makes relatively low-viscosity lava
C) a type of metal that tends to create stratovolcanoes when eruptions occur
D) a type of mineral that is the main ingredient of sea salt
E) another name for lava
Answer: B
39) How did the lunar maria form?
A) Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins.
B) The early bombardment created heat that melted the lunar surface in the regions of the maria.
C) Volatiles escaping from the Moon's interior heated and eroded the surface in the regions of the maria.
D) The giant impact that created the Moon left smooth areas that we call the maria.
E) The maria are the result of gradual erosion by micrometeorites striking the Moon.
Answer: A
40) Why does the Moon have a layer of powdery "soil" on its surface?
A) Large impacts shattered lunar rock to make this soil.
B) The soil exists because the Moon accreted from powdery material after a giant impact blasted Earth.
C) Volatiles escaping from the Moon's interior bubble upward and make the soil.
D) The soil is the result of the same processes that make powdery sand on Earth.
E) It's the result of gradual erosion by micrometeorites striking the Moon.
Answer: E
41) 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.
Answer: D
42) Why do we think Mercury has so many tremendous cliffs?
A) They were probably carved in Mercury's early history by running water.
B) They were probably formed by tectonic stresses when the entire planet shrank as its core cooled.
C) They probably formed when a series of large impacts hit Mercury one after the other.
D) They are almost certainly volcanic in origin, carved by flowing lava.
E) They represent one of the greatest mysteries in the solar system, as no one has suggested a reasonable hypothesis for their formation.
Answer: B
43) Olympus Mons is a
A) shield volcano on Mars.
B) stratovolcano on Mercury.
C) large lava plain on the Moon.
D) shield volcano on Venus.
E) stratovolcano on the Moon.
Answer: A
44) Valles Marineris is a
A) large valley on the Moon.
B) vast plain on Mars.
C) huge series of cliffs on Mercury.
D) large canyon on Mars.
E) large canyon on Venus.
Answer: D
45) Which of the following does not provide evidence that Mars once had large amounts of flowing water?
A) the presence of what looks like dried-up riverbeds
B) the presence of impact craters that appear to have formed in mud
C) the presence of vast canals discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell
D) rocks of many different types jumbled together, as would occur if there had once been a great flood in the region, found by the Mars Pathfinder
E) some very old craters that appear to have been eroded by rain
Answer: C
46) The polar caps on Mars are composed of
A) pure solid carbon dioxide.
B) pure water ice.
C) mostly solid carbon dioxide and some water ice.
D) mostly water ice and some solid carbon dioxide.
E) There are no polar caps on Mars.
Answer: C
47) How have we been able to construct detailed maps of surface features on Venus?
A) by studying Venus from Earth with powerful telescopes
B) by studying Venus with powerful optical telescopes on spacecraft that were sent to orbit Venus
C) by making computer models of geological processes on Venus
D) by using radar from spacecraft that were sent to orbit Venus
E) by landing spacecraft on the surface for close-up study
Answer: D
48) Which two geological processes appear to have been most important in shaping the present surface of Venus?
A) impacts and volcanoes
B) impacts and tectonics
C) tectonics and erosion
D) volcanoes and tectonics
E) volcanoes and erosion
Answer: D
49) Which of the following show evidence of ancient river beds?
A) the Moon
B) Mercury
C) Venus
D) Mars
E) all of the above
Answer: D
50) Spacecraft have landed on all the terrestrial worlds except
A) Mercury.
B) Venus.
C) Moon.
D) Mars.
E) Spacecraft have landed on all of the terrestrial worlds.
Answer: E
51) What process has shaped Earth's surface more than any other?
A) impact cratering
B) volcanism
C) plate tectonics
D) erosion
E) acid rain
Answer: C
52) Why are there fewer large craters on the seafloor than on the continents?
A) The seafloor crust is younger than the continental crust.
B) The oceans slow large impactors and prevent them from making craters.
C) The oceans erode away craters faster than erosion processes on land.
D) Large impactors primarily strike land masses.
E) Large impactors aim for life-forms such as dinosaurs.
Answer: A
53) 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.
Answer: B
54) Why is continental crust lower in density than seafloor crust?
A) Continental crust is made from remelted seafloor crust and therefore only the lower-density material rises to form it.
B) Continental crust is made from volcanic rock called basalt, which is lower in density than what the seafloor crust is made from.
C) Continental crust is made of rock, while seafloor crust has more metals.
D) Seafloor crust is more compact due to the weight of the oceans, but it is made of the same material as the continental crust.
E) Continental crust is actually denser than seafloor crust.
Answer: A
55) Which of the following is not evidence for plate tectonics on Earth?
A) some continental boundaries fit together like pieces of a jigsaw puzzle
B) similar rocks and fossils are found in different continents
C) high ocean ridges between the continents
D) existence of volcanoes
E) earthquakes
Answer: D
56) 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
Answer: A
57) How long, approximately, do geologists estimate it takes for the entire seafloor to be replaced due to plate tectonics?
A) 2 million years
B) 20 million years
C) 200 million years
D) 2 billion years
E) longer than the age of the solar system
Answer: C
58) What drives the motion of the tectonic plates on Earth?
A) convection cells in the mantle
B) lava flows in trenches along the sea floor
C) the Coriolis force
D) Earth's magnetic field
E) tidal forces
Answer: A
59) 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.
Answer: C
60) Deep trenches in the ocean mark places where
A) one plate slides under another, returning 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.
Answer: A
61) Some of the oldest continental crust on Earth lies in
A) Hawaii.
B) California.
C) the Great Plains.
D) the deep South.
E) Northeastern Canada.
Answer: E
62) 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
Answer: C
63) The geysers and hot springs of Yellowstone National Park result from
A) thin continental crust separating and creating a rift valley.
B) plumes of hot mantle rising in a hot spot within a plate.
C) plates that have slipped sideways relative to each other, creating a fault.
D) a plate that has run up against an existing continental plate.
E) a fault.
Answer: B
9.2 True/False Questions
1) The strength of a rock depends on its composition, its temperature, and the surrounding pressure.
Answer: TRUE
2) Higher temperatures make rocks weaker.
Answer: TRUE
3) Very high pressures, like those found deep within planetary interiors, can compress rocks so much that they stay solid even when temperatures are high enough to melt them under ordinary conditions.
Answer: TRUE
4) Smaller worlds generally have thinner lithospheres.
Answer: FALSE
5) Earth is the only planet in the solar system known to have plate tectonics.
Answer: TRUE
6) The magnetic and rotational north poles on Earth are the same.
Answer: FALSE
7) Mars has virtually no magnetic field.
Answer: TRUE
8) Erosion is the most important geological process on Venus.
Answer: FALSE
9) There is no erosion of surface features on the Moon.
Answer: FALSE
10) In the inner solar system, the largest surface features are found on the largest planets.
Answer: FALSE
11) Earth is the only terrestrial planet to have experienced tectonic stresses and volcanic activity.
Answer: FALSE
12) Much of the land on the west coast of North America began as volcanic islands in the Pacific.
Answer: TRUE
13) Spreading centers are marked by mid-ocean ridges where hot mantle material rises upward and then spreads sideways.
Answer: TRUE
14) The process in which one plate slides under another is called subduction and is marked by deep ocean trenches.
Answer: TRUE
15) Spacecraft have landed on all of the terrestrial worlds.
Answer: TRUE
9.3 Short Answer Questions
1) How do the size and chemical composition of a planet determine its internal temperature?
Answer: Size is the most important factor in determining how rapidly a planet loses its internal heat. The larger a planet is, the deeper is the "insulation" that surrounds the core and keeps in the heat. The chemical composition of a planet determines the amount of radioactive elements present. Currently the terrestrial planets' primary source of heat is radioactivity.
2) Describe the three sources of internal heat of the terrestrial planets?
Answer: Accretion is heat generated by the agglomeration of planetesimals when the planet was formed. Differentiation is heat generated by the energy released as dense objects fall toward the center of a planet during the formation of the core of a planet. Radioactive decay generates heat by releasing nuclear energy when an unstable (radioactive) isotope decays into a more stable element.
3) Explain how we can estimate the geological age of a planetary surface from its number of impact craters.
Answer: Even though impacts still occur today, the vast majority of craters formed during the bombardment period that ended around 3.8 billion years ago. A surface region that is still saturated with craters must have remained essentially undisturbed for the last 3.8 billion years. In contrast, a surface region that has few craters indicates that the original craters must have been somehow "erased" since then.
4) What is the main visual difference between the lunar highlands and the lunar maria? What are the implications of this observation?
Answer: The lunar highlands are very heavily cratered and the lunar maria are generally smooth. (More specifically, the maria contain only 3 percent as many craters per unit area as the highlands.) The difference in the amount of craters shows that the maria formed after the highlands, at the end of the heavy bombardment phase of the solar system. Radiometric dating of rocks from the highlands and maria shows that the heavy bombardment phase lasted no longer than a few hundred million years.
5) What can we learn from the detailed shapes of craters?
Answer: The shapes of craters can tell us the type of terrain in which they formed and whether they have been subject to erosion. Craters that form in rocky surfaces usually have a simple bowl shape. Craters that form in icy ground may look as if they formed in mud. Craters that lack sharp rims and bowl-shaped floors have probably been reshaped over time by erosion.
6) What can we learn from studying a planet's magnetic field?
Answer: Planetary magnetic fields are created in their metallic inner cores. From studying magnetic fields we can learn about the size and fluidity of their cores, which in turn gives clues as to their formation.
7) Why do we think Mercury contracted within about a billion years after it formed?
Answer: The surface of Mercury is marked by long, high cliffs. Such features result from tectonic compression, but there are no corresponding features due to tectonic stretching. This suggests the whole planet contracted as it rapidly cooled in its early history. We can date the contraction from the age of the volcanic flows on its surface: volcanic (and all geologic) activity probably came to an abrupt halt as a result of the planet's contraction.
8) Briefly explain why Mercury, Venus, and the Moon do not have significant erosion. Relate erosional activity to the four planetary formation properties.
Answer: Mercury has a negligible atmosphere from the point of view of erosion, primarily due to its high temperature, related to its distance from the Sun. Its relatively small size also led to only a small amount of outgassing to form an atmosphere in the first place. The Moon also has a negligible atmosphere, primarily related to the inability of such a small world to create or retain an atmosphere. Venus has a great deal of atmosphere but very little erosion. Water erosion doesn't occur because the planet is too hot, related to its distance from the Sun. It lacks significant wind erosion because its slow rotation rate leads to very slow winds.
9) Suppose Mars had turned out to be significantly smaller than its current size, say about the size of our Moon. How would this have affected the number of geological features due to each of the four major geological processes?
Answer: If Mars were smaller, it would have undergone less volcanic and tectonic activity because its interior would have cooled more. With less atmosphere from less outgassing, it is likely that erosion would be less important as well. As a result, craters would be more widespread on the Martian surface.
10) Summarize some of the evidence suggesting that Mars once had flowing water.
Answer: It has what looks like dried-up riverbeds and impact craters that appear to have formed in mud; the Mars Pathfinder found rocks of many different types jumbled together, as would occur if there had once been a great flood in the region; some very old craters appear to have been eroded by rain.
11) Why is erosion more effective on Earth than on Venus or Mars?
Answer: Erosion on Earth arises primarily from processes involving water, but also from atmospheric winds. Venus has very little surface wind because of its slow rotation, and wind on Mars does little damage because of the low atmospheric pressure. On Earth, water contributes to erosion through processes such as rain and rivers breaking down mountains, carving canyons, and transporting sand and silt. Water also seeps into cracks and breaks them down from the inside.
12) Process of Science: Our theory of solar system formation suggests that larger planets cool more slowly than small ones. What does this suggest regarding geologic activity on Venus? Do we expect Venus to be geologically active? How did scientists test this hypothesis?
Answer: Since Venus is about Earth's size, we expect it to still have a hot interior and be active like Earth is. Radar observations of the Venusian surface showed evidence of tectonic activity and volcanoes.
13) Process of Science: Make a prediction from the theory of plate tectonics and then look to see if you can find an example on Earth that provides a test.
Answer: One possibility is that we should see evidence in ancient material such as particular rocks or fossils that various parts of the land that we see today were in very different environments in the past, e.g., fossils indicating that parts of Antarctica were once very warm or that rocks on the top of mountains were once underneath the sea. Another prediction is that we could actually measure the drift of the continents with very precise measurements, and this is indeed now possible with modern technology.
14) Process of Science: How can we test hypotheses about something that is postulated to exist in the past but that no longer exists today, such as free-flowing water on Mars?
Answer: A hypothesis must make predictions that are testable today, even if it concerns something that happened in the past. In the case of water on Mars, we would expect geological and mineralogical signatures to persist after the water has sublimated or otherwise disappeared and, indeed, orbital imagers and ground rovers have found several features that support the hypothesis.
15) Briefly explain why NASA chose Gale Crater as target site of exploration for Curiosity.
Answer: There are many exposed layers of tilted sedimentary rock on Mt. Sharp that dates to many different times over the past several billion years. Studying them will help us learn much more about Mars' history and perhaps give us insight as to whether Mars has ever been home to life.
16) What is the importance of "blueberries" found on Mars?
Answer: These tiny spheres are composed of minerals that suggest formation in a salty environment such as a pond or lake. The clumps of pebbles with rounded surfaces and sedimentary layers in the ancient streambed clearly indicate formation in flowing water.
9.4 Mastering Astronomy Reading Quiz
1) 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) a dust speck to a golf ball.
B) a golf ball to a baseball.
C) a dust speck to a basketball.
D) a golf ball to a beach ball.
Answer: B