Ch. 06: Homework

The level of each of the surface-shaping processes that occur on a planet throughout its history will determine how its surface appears. The terrestrial planets were formed in basically the same environment, so we can assume that the average frequency of impacts for all of the terrestrial planets has been about the same.In a hypothetical scenario where impacts are the only process that ever shape planetary surfaces, how would the surfaces of the terrestrial planets compare? (Tip: Note that "craters per area" refers to the number of craters in the same-sized region on each planet—for example, craters per square meter.)

A. All of the planets would have roughly the same number of craters per area.

You are looking down on Earth from the North Pole. Recall from Chapter 2 that Earth rotates counterclockwise when viewed from this vantage point. Click the box that says "Include Effects of Earth's Rotation." What happened to the tidal bulges?

A. The tidal bulges rotated a little counterclockwise.

Before you start the simulation, examine the setup. You are looking down on Earth from the North Pole.Are the sizes of the Earth and Moon approximately to scale in this image?

A. no

Before you start the simulation, examine the setup. You are looking down on Earth from the North Pole.Is the distance between the Moon and the Earth to scale in this image?

A. no

You are looking down on Earth from the North Pole. Recall from Chapter 2 that Earth rotates counterclockwise when viewed from this vantage point. Which astronomical body dominates the tides on Earth?

A. the Moon

Comparing objects in our Solar System can give us important clues toward understanding their properties that we wouldn't obtain through just studying each object independently. Comparing Earth's Moon to those of the other planets may also help us understand more about it. Examine this table and choose the statements below it that match your observations.

B and C B.The Earth's moon is unique in that it is much larger than the moons of the other inner planets. C.Only half of the inner planets have moons.

-article- What is different about the geological features of sites in this study compared with those of sites where RSLs were previously found?

B. Many previous RSL sites were inside impact craters where extensive underground layers holding water could have been penetrated by impactors and those penetrations would be responsible for the suspected water.

You are looking down on Earth from the North Pole. Recall from Chapter 2 that Earth rotates counterclockwise when viewed from this vantage point. Click the boxes that say "Include Effects of Earth's Rotation" and "Play Animation." Why are there two high tides? That is, what causes the tide on the side of the Earth away from the Moon?

B. The difference in force between the two sides of the planet causes both to bulge out.

You are looking down on Earth from the North Pole. Recall from Chapter 2 that Earth rotates counterclockwise when viewed from this vantage point. Click the boxes that say "Include Effects of Earth's Rotation" and "Include Sun's Gravity." What happened to the tides when you added the Sun to the simulation?

B. The strength of the tidal bulges became stronger.

How would you explain the difference in cratering between these two pictures?

B. The surface on the right has experienced more recent volcanism or erosion than the surface to the left.

Before you start the simulation, examine the setup. You are looking down on Earth from the North Pole. In this position, is the east coast of North America experiencing high or low tide?

B. high tide

Before you start the simulation, examine the setup. You are looking down on Earth from the North Pole.Are the tides shown to scale?

B. no

If all the inner planets formed from the same processes, why would Earth and Mars be the only ones with moons? One possibility is that it was difficult for the inner rocky planets to acquire moons, and Earth and Mars obtained theirs only through some lucky event. We can compare the three moons to each other and to other objects in the inner Solar System to get an idea of what might have happened. Shown below are images of the moons, with information about their sizes and densities. Also shown are the sizes and densities of some other relatively small objects in the inner Solar System. Based on the images of the moons and the properties of the objects listed, which of the following statements is correct?

C. Phobos and Deimos have properties that suggest that they are the same type of object as c-type asteroids.

-article- Explain why the presence of RSL in Valles Marineris makes the canyon more interesting than previously thought.

C. The low latitudes, high elevations, and frequency of RSL at these canyon ridges and isolated peaks, make them more likely to be from recent water flows.

You are looking down on Earth from the North Pole. Recall from Chapter 2 that Earth rotates counterclockwise when viewed from this vantage point. Click the boxes that say "Include Effects of Earth's Rotation" and "Include Sun's Gravity." Now, run the simulation. Stop the simulation when the Moon is at first quarter. Remove the check mark from the "Include Sun's Gravity" box. What changed about the tides when you removed the Sun?

C. The strength of the tidal bulges became stronger.

You are looking down on Earth from the North Pole. Recall from Chapter 2 that Earth rotates counterclockwise when viewed from this vantage point.Click the box that says "Include Effects of Earth's Rotation." Click the box that says "Include Sun's Gravity." Now, run the simulation. Stop the simulation when the Moon is full. What changed about the tides when you added the Sun back in?

C. The strength of the tidal bulges became stronger.

This image shows the relative sizes of the terrestrial planets and their order from the Sun (closest toward the left, farthest toward the right). Assume that, based on crater counts, the geological age of the planetary surfaces from oldest to youngest is Mercury, Mars, Venus, Earth. Based on the information above, which of the following properties of a planet is most important in determining its level of recent geological activity?

C. size

Earth is composed of differentiated layers with distinctive attributes. Starting with the center and moving outward, indicate the proper sequence of the layers.

Center: 1) Solid core 2) Liquid core 3) Mantle 4) Crust 5) Atmosphere Exterior:

Identify these Solar System objects from their surface image by placing them in order from closest to the Sun to farthest away (assume the Moon is in such a location that it appears as a full Moon).

Closest to the Sun - Farthest (left to right) dark grey, lighter grey/blue, green, light tan, dark tan/brow

It is unlikely that the Moon formed elsewhere and was captured by Earth's gravity, since it may be impossible for the Earth to capture an object as large as the Moon. It is also of note that the Moon contains an unusually low quantity of volatiles, which are materials like water that are easily vaporized at high enough temperatures. Based on this, and given the moon's density, which of the following formation scenarios of the Moon most closely matches our observations?

D. The Moon accreted from the debris of the impact of a large object with the surface of the Earth.

Observations show that, in general, larger planets and moons have had geological activity more recently than smaller bodies have. All of the planets show past signs of volcanism, tectonics, and/or erosion, but only the larger ones are still geologically active today. Why is this? One reason has to do with the planet's interior. Most of the heat inside of Earth is left over from the accretion process during Earth's formation. What would you expect to have happened as the Earth (or any other planet) cooled after its formation? (Tip: You may watch this animation for a reminder of how each of the geological processes works. Click on each process at the end of the initial animation for more detailed information.)

D. The hard crust thickened, closing off volcanic vents, and the mantle began to solidify, slowing the motion that causes volcanism and tectonics.

Why did the authors of the simulation make the scaling choices they did?

D. The scaling choices were made so that the tidal distortion effect from the Moon on Earth could actually be seen and appreciated.

The similarity of Mars' tiny moons to asteroids suggests that they wandered away from the nearby asteroid belt and were captured by Mars' gravity. It is difficult to explain, however, how a relatively small planet like the Earth would be capable of capturing an object as large as the Moon. If it wasn't captured, then it must have either formed simultaneously with the Earth or separated from the Earth due to some event that happened later. We can get an idea of which scenarios are reasonable by looking at the composition of the two, which we can gather from their densities. Examine the figure below, which shows the approximate density of the Earth's layers in g/cm3. If the density of the Moon is 3.34 g/cm3, which layer of the Earth is it most similar to?

D. crust

Some surfaces have experienced more recent geological activity (like volcanism or erosion) that wiped out previously existing craters. They are referred to as "geologically younger" than surfaces that have not experienced activity. We can therefore use crater counts to determine the "age" of a surface, approximating how long ago the last geological event occurred in that area. Using this technique (and assuming these pictures are representative of the crater density on the entire planet), rank the planets in order of their geological age, from oldest to youngest.

Oldest to Youngest: (left to right) Grey with craters, yellow, red, grey lines

-article- Pt. 1 - Look up the term "hydrated salts." Why does the presence of hydrated salts indicate the presence of water? Pt. 2 - Are there any large deposits of hydrated salts on Earth?

Pt. 1: A and E A.Hydrated salts are unlikely to form from shallow ground ice in equatorial canyons, therefore they suggest recent surface water flows. E.Hydrated salts occur when salts form in water (aqueous) solutions, therefore they could indicate the recent flow of surface water. Pt. 2: Yes

Label the interior areas of the terrestrial planets shown.

Venus: C) Crust Earth: B) solid inner core (yellow center), D) liquid outer core (orange) Moon: A) Core Mars: E) Mantle

Why are these planets so different? To answer this, we must start with an understanding of the processes that cause planetary surfaces to change: volcanism, tectonics, erosion, and impacts. Watch the AstroTour Animation on Processes that Shape the Planets, and use what you learn to match each item to the corresponding process.

Volcanism/tectonics: Rising mantle material Erosion: Wind, ice Impacts: Meteorites

Properly identify the features of an impact crater using this image of a Moon crater.

far left: D) Ray top right: A) Secondary crater upper-center: C) Crater wall bottom: B) Central peak

Label the various processes associated with tectonism. BEA

orange peak, upward arrows: B) Spreading center Nazca plate downward arrow: E) Subduction top right corner: A) compression bottom left corner: D) Spreading bottom right corner: C) Fault

Match the geological process with the image of a landscape created by that process.

top left: B) Impact crater top right: C) Tectonism bottom left: D) Volcanism bottom right: A) Erosion