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Chapter 11: Problem 21

What is the Martian crustal dichotomy? What is the evidence that the southern highlands are older than the northern lowlands?

Short Answer

Expert verified
The 'Martian crustal dichotomy' refers to the clear difference between the Northern Lowlands and Southern Highlands on Mars. The Southern Highlands, having a more rugged and cratered terrain, is reputedly older than the Northern Lowlands. The evidence lies in the number of craters (more craters mean older surface) and the interpretation of volcanic activity or tectonic movement that caused the smoother landscape of the Northern Lowlands, indicating it is relatively newer.

Step by step solution

01

Understanding Martian Crustal Dichotomy

The Martian crustal dichotomy is the difference in land surfaces between the Northern and Southern hemispheres of Mars. In the Northern hemisphere, the surface of Mars is mostly smooth and has a lot of plains, known as the Northern Lowlands. In contrast, the Southern hemisphere has a heavily cratered and rugged terrain, known as the Southern Highlands.
02

Assessing Age Based on Surface Features

Craters are a sign of age in planetary geology. Since the Southern Highlands has more craters, it implies they have been there for a longer time and hence, are older. This is because over time, meteor impacts have caused these craters, and they take millions of years to accumulate.
03

Understanding Role of Geological Processes

The Northern Lowlands, in comparison, are smoother. This has been interpreted to be caused by volcanic activity or tectonic activity which 'resurfaced' the region, hiding old craters. These geological processes are relatively more recent thus, suggesting that the northern lowlands are younger.

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Most popular questions from this chapter

You are to put a spacecraft into a synchronous circular orbit around the Martian equator, so that its orbital period is equal to the planet's rotation period. Such a spacecraft would always be over the same part of the Martian surface. (a) Find the radius of the orbit and the altitude of the spacecraft above the Martian surface. (b) Suppose Mars had a third moon that was in a synchronous orbit. Would tidal forces make this moon tend to move toward Mars, away from Mars, or neither? Explain.

On Mars, the difference in elevation between the highest point (the summit of Olympus Mons) and the lowest point (the bottom of the Hellas Planitia basin) is \(30 \mathrm{~km}\). On Earth, the corresponding elevation difference (from the peak of Mount Everest to the bottom of the deepest ocean) is only \(20 \mathrm{~km}\). Discuss why the maximum elevation difference is so much greater on Mars.

If you could examine rock samples from the surface of Venus, would you expect them to be the same as rock samples from Earth? Would you expect to find igneous, sedimentary, and metamorphic rocks like those found on Earth (see Section 9-3)? Explain your answers.

Although the Viking Lander 1 and Viking Lander 2 landing sites are \(6500 \mathrm{~km}\) apart and have different geologic histories, the chemical compositions of the dust at both sites are nearly identical. (a) What does this suggest about the ability of the Martian winds to transport dust particles? (b) Would you expect that larger particles such as pebbles would also have identical chemical compositions at the two Viking Lander sites? Why or why not?

Use the Starry Night Enthusiast \({ }^{\mathrm{TM}}\) program to observe the appearance of Mars. Select Favourites \(>\) Guides \(>\) Atlas from the menu. Select View \(>\) Celestial Grid from the menu to turn this option off. Open the Find pane and click the menu button for Mars and choose Centre from the menu. Close the Find pane and then use the Zoom controls in the toolbar to set a field of view of approximately \(58^{\prime \prime} \times 40^{\prime \prime}\). (a) Set the Time Flow Rate to 1 hour and then run Time Forward. Describe what you see. (b) Stop time flow. Change the Time Flow Rate to 1 lunar month. Run Time Forward again. Describe what you see. Using a diagram like Figure 4-6, explain the changes in the apparent size of the planet. (c) Stop time flow and zoom out to a field of view of approximately \(\mathbf{2}^{\prime} \times \mathbf{1}^{\prime}\). Change the time and date in the toolbar to \(12: 00: 00\) A.M. on August 28, 2003, to see Mars during a very favourable opposition. You will see Mars and its two moons, Phobos and Deimos. In the toolbar, set the Time Flow Rate to 1 minute. Record the date and time in the display, and note the position of Phobos (the inner moon). Click the Run Time Forward and single time step button (the rightmost time control button) to advance time until Phobos returns to approximately the same position relative to Mars. Record the date and time in the display. From your observations, what is the orbital period of Phobos? How does your result compare with the orbital period given in Appendix 3? (d) Repeat part (c) for Deimos (the outer moon).
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