B) size and solid surface similar to terrestrial planets; distance similar to jovian planets
C) size and distance similar to terrestrial planets; gaseous surface and composition similar to jovian planets
D) solid surface and density similar to terrestrial planets; temperature and composition similar to jovian planets
E) solid surface and temperature similar to terrestrial planets; distance and density similar to jovian planets
24) Astronomers have decided that, rather than being a planet, Pluto is really just a large member of
A) the asteroid belt.
B) the Kuiper belt.
C) the Oort cloud.
D) the moon system around Neptune.
E) an extrasolar planetary system.
25) Which of the following is not a pattern of motion in our solar system?
A) Planets all orbit in the same direction.
B) Planets all rotate in the same direction.
C) Planets all orbit the same direction as the Sun's spin.
D) Large planets all have many moons orbiting them.
7.2 True/False Questions
1) Oceans cover more of Earth's surface than land.
2) All four of the giant outer planets–Jupiter, Saturn, Uranus, and Neptune–have rings.
3) The jovian planets have no solid surface.
4) The planet Uranus held a special place in the mythology of the ancient Romans.
5) All planets orbit the Sun in the same direction (counterclockwise as viewed from above Earth's North Pole).
6) All the planets in the solar system have at least one moon.
7) All comets orbit the Sun in the same direction as the planets.
8) The more massive planets in the solar system tend to be less dense than the lower mass planets.
7.3 Short Answer Questions
1) What is comparative planetology, and what is its basic premise?
Answer: Comparative planetology is the approach we use to study and understand our solar system. It involves comparing the worlds of our system, including planets, moons, asteroids, and comets, to one another. Its basic premise is that the similarities and differences among the worlds can be traced to common physical processes.
2) In the 1800s, many people assumed that Venus would have tropical temperatures, but instead it is very hot. Explain why tropical temperatures would have made sense given what was known in the 1800s, and why Venus instead turns out to be very hot.
Answer: If Venus had an atmosphere similar to ours–a reasonable assumption in the 1800s–it would have tropical temperatures. But instead it has a thick carbon dioxide atmosphere that causes a very strong greenhouse effect, thus explaining its very hot surface.
3) What are some of the things that make Earth unique in the solar system?
Answer: It is the only planet with an oxygen-rich atmosphere and liquid water on its surface (although there are hints that there may be liquid water on some of the moons around the jovian planets). Its surface temperature is such that water can exist in three phases: solid, liquid, and gaseous. Compared to its size, Earth also has by far the largest moon in the solar system, so much so that some astronomers consider it a double planet. Finally, Earth is the only planet we know of that harbors life.
4) Briefly summarize the differences between terrestrial and jovian planets.
Answer: Terrestrial planets are metallic or rocky in composition, close to the Sun, have higher average density, have a solid surface, are warmer at the surface, and have few if any moons. jovian planets are gaseous in composition, lower in density, have no solid surface, are farther from the Sun, and have rings and moons.
For the following questions, classify the spacecraft in one of these categories: A. Earth orbiter B. flyby C. planetary orbiter D. lander
5) Hubble Space Telescope
6) the main part of the Galileo spacecraft (i.e., not its atmospheric probe)
8) Voyager 2
Choose from these spacecraft in the following questions. A. Magellan B. Voyager 2 C. Apollo 11 D. Galileo E. Viking 1, 2 9) visited all four giant planets between 1979 and 1989
10) mapped most of the surface of Venus with radar observations from Venusian orbit
11) carried the first humans to the Moon on July 20, 1969
12) dropped a probe into Jupiter on December 7, 1995
13) landed on Mars in 1976
Choose from the spacecraft below for the following questions: A. Curiosity B. New Horizon C. Cassini D. Hubble Space Telescope E. Galileo orbiter 14) used a sky crane to lower itself to the surface of Mars
15) carried a probe that landed on Titan
16) is soon to become the first spacecraft to fly by Pluto
17) has been collecting high-resolution images of Jupiter and its moons since 1995
18) is currently in orbit around Saturn
19) the only spacecraft listed that remains in Earth's orbit
20) Process of Science: In order for us to understand how the solar system got to be that way it is, we must identify the major solar system patterns that our formation theory must explain. Name 3 patterns of motion or planetary arrangement/location that our theory should be able to explain.
1. Planets orbit in the same direction.
2. Orbital direction is the same direction as the Sun's spin.
3. Most planets spin the same direction that they orbit.
4. Bigger planets are in the outer solar system.
5. Large planets have many moons.
6. Planets lie in approximately the same plane.
21) Process of Science: Pluto is no longer considered a planet. Explain the new discoveries that led to this change.
Answer: In recent years, astronomers have found numerous other bodies that orbit beyond the orbit of Neptune. These so-called Kuiper Belt objects share similar properties in being round, icy bodies and one is known to be larger than Pluto. We now recognize that Pluto is just one of a large collection of objects in the Solar System, rather the unique, individual bodies that are the planets.
22) Process of Science: Explain the varied ways in which we continue to explore the Solar System.
Answer: We learned about the nature of planets through observations of their motions with our eye and telescopes. We continue to study the planets and other Solar System objects with ground-based telescopes but also use space telescopes and spacecraft. Humans have landed on the Moon and returned with lunar samples. Robotic spacecraft have visited all the planets and provided our most detailed images of them, as well as in some cases sent probes to their surfaces or to into their atmospheres.
7.4 Mastering Astronomy Reading Quiz
1) Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?
A) All the planets orbit counterclockwise around the Sun.
B) The inner planets orbit the Sun counterclockwise while the outer planets orbit the Sun clockwise.
C) All the planets except Uranus orbit the Sun counterclockwise; Uranus orbits in the opposite direction.
D) The inner planets orbit the Sun clockwise while the outer planets orbit the Sun counterclockwise.
2) The terrestrial planets in our solar system are
A) Mercury, Venus, Earth, and Mars.
B) Jupiter, Saturn, Uranus, and Neptune.
C) Mercury, Venus, Earth, Mars, and Pluto.
D) Jupiter, Saturn, Uranus, Neptune, Pluto, and Eris.
3) The jovian planets in our solar system are
A) Mercury, Venus, Earth, and Mars.
B) Jupiter, Saturn, Uranus, Neptune, Pluto, and Eris.
C) Jupiter, Saturn, Uranus, and Neptune.
D) Io, Europa, Ganymede, and Callisto.
4) When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals except
B) carbon dioxide.
5) Which of the following statements about the asteroid belt is not true?
A) The combined mass of all the asteroids is roughly the same as the mass of Earth.
B) It is located between the orbits of Mars and Jupiter.
C) Asteroids in the asteroid belt orbit the Sun in the same direction that planets orbit the Sun.
D) Asteroids in the asteroid belt are made mostly of rock.
6) What is the Kuiper belt?
A) a region of the solar system that extends almost a fourth of the way to the nearest stars and contains a trillion comets with orbits going in all directions around the Sun
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"
14) Which of the following statements about Pluto is not true?
A) It has more in common with comets in the Kuiper belt than it does with the jovian planets.
B) It is orbited by at least three moons.
C) Its mass is less than 1% of Earth's mass.
D) It is the largest known object that is considered to be a dwarf planet.
15) The Cassini mission to Saturn consists of
A) an orbiter that orbits Saturn and a probe that descended to the surface of Titan.
B) a large spacecraft that flew by Saturn on its way to other planets.
C) an orbiter that orbits Saturn and a probe that descended into Saturn's atmosphere.
D) a spacecraft that orbits Saturn and a sample return mission that landed on Titan, scooped up a surface sample, and will return it to Earth.
16) Which planet (besides Earth) has been visited by the largest number of robotic spacecraft?
7.5 Mastering Astronomy Concept Quiz
1) Which of the following is not a major pattern of motion in the solar system?
A) Nearly all comets orbit the Sun in same direction and roughly the same plane.
B) Most of the solar system's large moons orbit in their planet's equatorial plane.
C) The Sun and most of the planets rotate in the same direction in which the planets orbit the Sun.
D) All of the planets orbit the Sun in the same direction—counterclockwise as viewed from above Earth's north pole.
2) Which of the following is not a major difference between the terrestrial and jovian planets in our solar system?
A) Terrestrial planets contain large quantities of ice and jovian planets do not.
B) Terrestrial planets orbit much closer to the Sun than jovian planets.
C) Terrestrial planets are higher in average density than jovian planets.
D) Jovian planets have rings and terrestrial planets do not.
3) Consider the following statement: "Rocky asteroids are found primarily in the asteroid belt and Kuiper belt while icy comets are found primarily in the Oort cloud." What's wrong with this statement?
A) Asteroids are not made of rock.
B) Comets are not icy.
C) The Kuiper belt contains icy comets, not rocky asteroids.
D) The Oort cloud has nothing to do with comets.
E) The statement is accurate as written.
4) Which of the following is not a real difference between asteroids and comets?
A) Asteroids orbit the Sun while comets just float randomly around in the Oort cloud.
B) Most asteroids are located much nearer to the Sun than most comets.
C) It is thought that comets are far more numerous than asteroids.
D) Asteroids are made mostly of rock and comets are made mostly of ice.
5) The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
A) Venus does not have a moon.
B) Jupiter has a very small axis tilt.
C) Saturn has no solid surface.
D) The diameter of Earth's Moon is about 1/4 that of Earth.
6) Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is
A) about the same.
B) much larger.
C) much smaller.
D) just slightly less.
7) How is Einstein's famous equation, E= mc2, important in understanding the Sun?
A) It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each day.
B) It explains why the Sun's surface temperature is about 6,000°C.
C) It explains why the Sun is so massive.
D) It explains why the Sun has a magnetic field strong enough influence the atmospheres of the planets.
8) Venus has a higher average surface temperature than Mercury. Why?