Review Questions
Venus rotates backward and Uranus and Pluto spin about an axis tipped nearly on its side. Based on what you learned about the motion of small bodies in the solar system and the surfaces of the planets, what might be the cause of these strange rotations?
What is the difference between a differentiated body and an undifferentiated body, and how might that influence a body’s ability to retain heat for the age of the solar system?
What does a planet need in order to retain an atmosphere? How does an atmosphere affect the surface of a planet and the ability of life to exist?
Which type of planets have the most moons? Where did these moons likely originate?
What is the difference between a meteor and a meteorite?
Explain our ideas about why the terrestrial planets are rocky and have less gas than the giant planets.
Do all planetary systems look the same as our own?
What is comparative planetology and why is it useful to astronomers?
What changed in our understanding of the Moon and Moon-Earth system as a result of humans landing on the Moon’s surface?
If Earth was to be hit by an extraterrestrial object, where in the solar system could it come from and how would we know its source region?
List some reasons that the study of the planets has progressed more in the past few decades than any other branch of astronomy.
Imagine you are a travel agent in the next century. An eccentric billionaire asks you to arrange a “Guinness Book of Solar System Records” kind of tour. Where would you direct him to find the following (use this chapter and Appendix F and Appendix G):
- the least-dense planet
- the densest planet
- the largest moon in the solar system
- excluding the jovian planets, the planet where you would weigh the most on its surface (Hint: Weight is directly proportional to surface gravity.)
- the smallest planet
- the planet that takes the longest time to rotate
- the planet that takes the shortest time to rotate
- the planet with a diameter closest to Earth’s
- the moon with the thickest atmosphere
- the densest moon
- the most massive moon
What characteristics do the worlds in our solar system have in common that lead astronomers to believe that they all formed from the same “mother cloud” (solar nebula)?
How do terrestrial and giant planets differ? List as many ways as you can think of.
Why are there so many craters on the Moon and so few on Earth?
How do asteroids and comets differ?
How and why is Earth’s Moon different from the larger moons of the giant planets?
Where would you look for some “original” planetesimals left over from the formation of our solar system?
Describe how we use radioactive elements and their decay products to find the age of a rock sample. Is this necessarily the age of the entire world from which the sample comes? Explain.
What was the solar nebula like? Why did the Sun form at its center?