Chapter 9
13. Summarize the four main hypotheses for the origin of the Moon.
1) The fission hypothesis, the Earth and Moon were formed together as one and separated early in their history. 2) Sister hypothesis, the Earth and Moon formed together but independently of each other 3) Capture hypothesis, Moon was formed elsewhere in the solar system and was later captured by Earth 4) Giant impact Hypothesis, A large maybe Mars-sized object grazed earth and ejected materials from the impactor and earth. These materials condense to form the Moon.
How large is an impact crater compared to the size of the impactor?
10 times larger
What kind of surface features may result from tectonics?
Mountains, valleys, volcanoes, and cliffs
Questions from Book
Questions from Book
Which internal energy source is the most important in continuing to heat the terrestrial planets today?
Radioactivity
2. Why does the Moon not have an atmosphere?
The Moon has a relatively small mass and therefore gravity is not strong enough to hold an atmosphere.
1. What is the composition of the Moon, and how does it compare to the composition of Earth? Of Mercury?
The Moon is mostly silicates, like the mantel of the Earth. The Earth has an iron core, and so does Mercury, but the moon does not. Earth has liquid water, the moon the does not.
What type of stresses broke Earth's lithosphere into plates?
The circulation of convection cells in the mantle, which dragged against the lithosphere.
Which of the following describes tectonics?
The disruption of a planet's surface by internal stresses.
Which of the following describes volcanism?
The eruption of molten rock from a planet's interior to its surface.
Which of the following describes impact cratering?
The excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface.
8. With no wind or water erosion of rocks, what is the mechanism for the creation of the lunar "soil?"
The lunar soil is caused by micro-meteorite/meteorite strikes on the surface. Even the smallest of meteorites reach the surface breaking up the rocks on the surface over billions of years
The core, mantle, and crust of a planet are defined by differences in their
composition.
The main process by which heat flows upward through the lithosphere is
conduction.
When we say that a liquid has a high viscosity, we mean that it
flows slowly like honey.
Steep-sided stratovolcanoes are made from lava that
has a high viscosity.
Shallow-sloped shield volcanoes are made from lava that
has a medium viscosity.
Volcanism is more likely on a planet that
has high internal temperatures.
A planet is most likely to have tectonic activity if it has
high internal temperature.
Heat escapes from a planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the
infrared.
The terrestrial planet cores contain mostly metal because
metals sank to the center during a time when the interiors were molten throughout.
The lithosphere of a planet is the layer that consists of
the rigid rocky material of the crust and uppermost portion of the mantle.
When we see a region of a planet that is not as heavily cratered as other regions, we conclude that
the surface in the region is younger than the surface in more heavily cratered regions.
The relatively few craters that we see within the lunar maria
were formed by impacts that occurred after those that formed most of the craters in the lunar highlands.
31. The Moon has too little iron, Mercury too much. How can both of these anomalies be the result of giant impacts? Explain how the same process can yield such apparently contradictory results.
A large impact with Mercury would remove much of its crust. If this happened after the planet had differentiated, Mercury would lose its non-metal crust. If the moon was formed by a giant impact with the earth, it would be made from the non-metallic crust of the Earth.
What is basalt?
A type of rock that makes relatively low-viscosity lava.
Which internal energy source produces heat by converting gravitational potential energy into thermal energy?
Accretion and differentiation
The three principal sources of internal heat of terrestrial planets are
Accretion, differentiation, and radioactivity.
33. The Moon was once closer to Earth than it is now. When it was at half its present distance, how long was its period of revolution? (See Orbits and Gravity for the formula to use.)
At half its present distance, Kepler's third law tells us that the Moon must have had a period shorter by a factor of two to the 3/2 power, or 2.83. Therefore the period was 27.3 days/2.83 = 9.6 days. (p^2=a^3)
What are the conditions necessary for a terrestrial planet to have a strong magnetic field?
Both a molten metallic core and reasonably fast rotation.
Ch 9 Testbank Questions
Ch 9 Testbank Questions
Rank the five terrestrial worlds in order of size from smallest to largest.
Moon, Mercury, Mars, Venus, Earth
Which two properties are most important in determining the surface temperature of a planet?
Distance from the Sun and atmosphere.
Which of the terrestrial worlds has the strongest magnetic field?
Earth
Which of the following worlds have the thinnest lithospheres?
Earth and Venus
What is the most important factor that determines the thickness, and therefore strength, of the lithosphere?
Internal temperature
Why does Earth have the strongest magnetic field among the terrestrial worlds?
It is the only one that has both a partially molten metallic core and reasonably rapid rotation.
Which of the following best describes convection?
It is the process in which warm material expands and rises while cool material contracts and falls.
25. How might a crater made by the impact of a comet with the Moon differ from a crater made by the impact of an asteroid?
It would be hard to distinguish between the two types of impacts. Craters tend to be circular due to the explosion of the impactor. The size depends on the speed and mass of the impactor. The speeds for both comets and asteroids would be similar. In a comet-made crater, you may be able to find evidence of water if the crater has a permanently-shaded region.
Which of the following has virtually no effect on the structure of a planet?
Its magnetic field.
Which of the following most likely explains why Venus does not have a strong magnetic field?
Its rotation is too slow.
Which of the following does not have a major effect in shaping planetary surfaces?
Magnetism
28. At the end of the section on the lunar surface, your authors say that lunar night and day each last about two Earth weeks. After looking over the information in the chapter on the Earth, Moon, and Sky, and this chapter about the motions of the Moon, can you explain why? (It helps to draw a diagram for yourself.)
The moon always faces the same side towards the earth, so after one complete revolution of earth, about 29 days, the moon has also rotated on its axis once. Thus 2 weeks of daylight and 2 weeks of darkness.
Under what circumstances can differentiation occur in a planet?
The planet must have a molten interior.
What is differentiation in planetary geology?
The process by which gravity separates materials according to density.
Which of the following describes erosion?
The wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather.
11. Explain the evidence for a period of heavy bombardment on the Moon about 4 billion years ago.
There are many more craters in the highlands compared to the seas or maria--about 10 times as many. Highland rock samples have been radioactively dated to be about 4.2 billion years old while the maria has been dated to about 3.8 billion years old. If bombardment was constant, the highlands would have to be 10 times older than the maria regions. They are not 10 x older so a lot of the craters must have been formed just before the maria was created about 4 billion years ago.
Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones?
They have relatively more surface area compared to their volumes.
What are the circumstances under which convection can occur in a substance?
When the substance is strongly heated from underneath.
23. Galileo thought the lunar maria might be seas of water. If you had no better telescope than the one he had, could you demonstrate that they are not composed of water?
You could look for reflections of the water. Seas should reflect the sunlight and the marias do not do this.