Chapter 6

Which of the following lists the planets of our solar system in the correct order from closest to farthest from the Sun?Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
How does the Sun’s mass compare with that of the planets?It is a thousand times more massive than all the planets combined.
What’s unusual about our Moon?It’s surprisingly large relative to the planet it orbits.
The planet closest in size to Earth isVenus
Which planet has the highest average surface temperature, and why?Venus, because of its dense carbon dioxide atmosphere
According to modern science, what was the approximate chemical composition of the solar nebula?98% hydrogen and helium, 2% everything else
What are the main constituents of the jovian planets?hydrogen and helium
Where did the elements heavier than hydrogen and helium come from?They were produced inside stars.
Which planet, other than Earth, has visible water ice on it?Mars
Suppose you view the solar system from high above Earth’s North Pole. Which of the following statements about planetary orbits will be true?All the planets orbit counterclockwise around the Sun.
Planetary orbits in our solar system are:fairly circular and in the same plane.
What do we mean by accretion in the context of planet formation?the growth of planetesimals from smaller solid particles that collided and stuck together
The jovian planets in our solar system are _________.Jupiter, Saturn, Uranus, and Neptune
In essence, the nebular theory holds that _________.our solar system formed from the collapse of an interstellar cloud of gas and dust
Which of the following did not occur during the collapse of the solar nebula?concentrating denser materials nearer the Sun
Which lists the major steps of solar system formation in the correct order?collapse, condensation, accretion
Leftover ice-rich planetesimals are calledComets
The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from?They were produced by stars that lived and died before our solar system was born.
According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?It got hotter, its rate of rotation increased, and it flattened into a disk.
Which of the following types of material can condense into what we call ice at low temperatures?hydrogen compounds
According to modern scientific dating techniques, approximately how old is the solar system?4.5 billion years
According to our theory of solar system formation, what are asteroids and comets?leftover planetesimals that never accreted into planets
What do we mean by the frost line when we discuss the formation of planets in the solar nebula?It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ice to condense.
What is the giant impact hypothesis for the origin of the Moon?The Moon formed from material blasted out of Earth’s mantle and crust by the impact of a Mars-size object.
Why are terrestrial planets denser than jovian planets?Only dense materials could condense in the inner solar nebula.
Where are most of the known asteroids found?between the orbits of Mars and Jupiter
Which of the following statements about the accelerations and gravitational forces between a planet and a star is true?Forces are equal and opposite; the planet is accelerated more than the star.
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?the law of conservation of angular momentum
Based on our current theory of Earth’s formation, the water we drink comes fromcomets that impacted Earth.
Which of the following is furthest from the Sun?a comet in the Oort cloud
According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system
What is the giant impact hypothesis for the origin of the Moon?The Moon formed from material blasted out of the Earth’s mantle and crust by the impact of a Mars-size object.
Which of the following is not a major pattern of motion in the solar system?Nearly all comets orbit the Sun in same direction and roughly the same plane.
Which of the following is not a characteristic of the inner planets?They all have substantial atmospheres.
Which of the following is the origin of almost all the large moons around the jovian planets?They were formed by condensation and accretion in a disk of gas around the planet.
If the freezing point of ices of all types were at a much lower temperature, what change would that imply for the formation of our solar system?The gas giants would have to form at a larger distance.
Which of the following statements about the recently-discovered object Eris is not true?It is thought to be the first example of a new class of object.
The following statements are all true. Which one counts as an “exception to the rule” in being unusual for our solar system?The diameter of Earth’s Moon is about 1/4 that of Earth.
Which of the following observations indicates that conditions on Mars may have been suitable for life in the past?There are dried-up riverbeds on Mars.
Astronomers now classify Pluto as really just a large member ofthe Kuiper belt.
Which moons are sometimes called the Galilean moons?the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto
Which of the following statements best explains why the planets orbit in nearly a single plane and in the same direction around the Sun?The planets formed from a disk of rotating gas.
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?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.
What do we mean by the period of heavy bombardment in the context of the history of our solar system?the first few hundred million years after the planets formed, which is when most impact craters were formed
Which planet listed below has the most extreme seasons?Uranus
Which of the following are relatively unchanged fragments from the early period of planet building in the solar system?All of the above
Which of the following discoveries would cause us to re-evaluate the nebular theory for forming planets?A star’s 5 terrestrial planets orbit in the opposite direction of its 3 jovian planets.
Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass?You’ll have 0.25 kilogram of the radioactive substance remaining.
A rock sample from the moon includes a mineral that contains small amounts of the radioactive isotope Potassium-40 and its daughter element Argon-40 (half-life of 1.3 billion years). This mineral would not form with any Argon-40. Consider a crystal with 7 atoms of Argon-40 for every 1 atom of Potassium-40. How many half-lives has this sample existed?3
Suppose you find a rock that contains some potassium-40 (half-life of 1.3 billion years). You measure the amount and determine that there are 5 grams of potassium-40 in the rock. By measuring the amount of its decay product (argon-40) present in the rock, you realize that there must have been 40 grams of potassium-40 when the rock solidified. How old is the rock?3.9 billion