Name: Date:
THE MOON PRE-LAB Using your lecture textbook and/or any other acceptable source of information, answer each question in complete sentences. Be sure to define any relevant terms.
1. Explain the following terms relating to lunar surface features. a. Maria (singular “Mare”):
b. Highlands:
c. Rille:
d. Wrinkle Ridge:
e. Rays:
2. Explain the following terms relating to processes that shape the lunar surface. a. Tectonic:
b. Volcanic:
c. Impact:
d. Dating by Superposition:
8–1 Name: Partners:
Date:
THE MOON LAB EXERCISE
LUNAR REGIONS
In completing this lab, you will view images found on the Astronomy lab website. Your instructor will direct you to the location.
The Earth, the Moon and the Sun are the most familiar astronomical objects in the sky. Of these, the Moon has been historically the most studied and most photographed by astronomers. Even a small telescope reveals an incredible profusion of lunar features. The most prominent are the lunar maria, which show as dark smooth areas surrounded by mountains. Almost all of the maria are on the earthside of the Moon and have lower elevation than the lighter highlands. The worksheet is a sketch of the Moon, the meandering lines outline maria and highlands.
1. Examine the images of the near and far sides of the moon on the website. Describe the similari- ties and differences.
2. Look carefully at the image of the near side of the Moon and the map of the moon on your table. Place M’s on the worksheet at the center of the major maria. How many maria did you find?
3. Estimate the fraction or percentage of the Earth side of the Moon that is maria.
4. Describe the general shape of the maria. Are there any major exceptions? If so, which ones?
5. Wrinkle ridges are sinuous, low, irregular ridges which are associated with the maria. Examine the image of Mare Serenitatis. Find a prominent wrinkle ridge in the maria, sketch it on your worksheet, and label it w.r.
6. Suggest how wrinkle ridges may have formed.
8–1 7. Based on the appearance of the maria, explain how they might have been formed.
8. Examine the image labeled ‘LeMonnier.’ How does the appearance of the crater LeMonnier in Mare Serenitatis confirm your answer to question 7?
CRATERS Craters are the circular depressions which are scattered over the lunar surface. They range in size from a hundred or so kilometers, such as Copernicus, Tycho and Kepler, to those so small they were seen only at ground level by the astronauts.
9. Locate Copernicus on the worksheet and note it by a small c.
Just northeast of Copernicus are the Appenine Mountains which form a southern border to Mare Imbrium. The image labeled ‘moonmap’ represents a region 10 in every direction centered on 20N latitude and 0 longitude.
In this region there are many impact craters. Generally they can be divided into three main profiles. Examine the images labeled ‘crater-a,’ ‘crater-b,’ and ‘crater-c.’ The figure below shows the cross sections of the three main crater types.
a) flat-floored b) flat floor c) bowl- shaped central mountain peak
8–3 10. Name an example of each of these crater types found in this region represented in the ‘moonmap’ image.
a.
b.
c.
11. Which type of crater is Copernicus?
12. a. Which of the three types of craters in question 10 tend to be the smallest? Which are the largest?
b. Do each of the three types occur in both the highlands and the maria?
13. Look carefully at the image labeled ‘Copernicus.’ It was taken by the Apollo 15 command module. The large crater to the far right near the horizon is Copernicus. Using the map, find the location of this image on the Moon and note it on the worksheet with a square.
14. The prominent large crater just to the left of the photo center is and you are look- ing toward the compass direction of .
15. Account for the appearance of the long, jumbled, gradual slope outside the crater rim by explaining how the crater might have been formed.
16. State how the activity that formed the crater might also explain the higher-than-normal number of small craterlets in the foreground of the photograph.
8–4 17. Between the crater identified in question 14 and Copernicus there is a winding line of small cra- terlets. Find these craterlets on your moon map. List two ways in which these are different from the craters studied previously. (Hint: Look at their arrangement and shape.)
18. Which of the Moon’s major surface-modifying processes produced this sinuous line of craterlets?
19. Rays are light streaks radiating from craters. Name a crater with extensive rays.
20. Give three reasons why you would not expect to find a crater with such an extensive ray system on the Earth.
RILLES AND FAULTS Rilles are narrow channels, some straight, some sinuous, often running hundreds of kilometers. Faults are cracks or dislocations of the lunar crust. Many straight rilles are faults, but faults also include The Alpine Valley (also known as Valles Alpes) near 50N, 0, and The Straight Wall (also known as Rupes Recta) near 20S, 10W.
21. Locate and name one prominent straight rille that is obviously a crustal fracture.
Sketch this rille on the worksheet.
22. Suggest how rilles and faults may have been formed.
Look at photograph B which was also taken by the Apollo 15 command module. It features two sinuous rilles as well as a long, oval depression and numerous craters.
8–5 23. With the exception of the lower right of the photograph, the terrain seems to be (highlands/maria).
24. The craters in a string near the center of the photo are like those of question 17. Thus, they are (impact/tectonic/volcanic) in origin.
25. Can you suggest how the two sinuous rilles were formed?
Lunar features can be classified by the means which formed them.
1) Impact features are caused by a very large size range of meteoroids crashing into the lunar surface. The larger objects penetrate the surface then explode. 2) Vulcanism causes flows of liquid magma from beneath the crust out onto and across the surface. Sometimes it is also responsible for uplifted features such as domes. 3). Tectonic activity results from moonquakes or other crustal shifts.
Some features show two processes, such as the maria. The general shapes of the maria were determined by gigantic meteoritic impacts which formed impact basins. The maria were then filled by vulcanism.
26. Characterize the following features as impact, tectonic, volcanic or some combination.
a) Copernicus b) The Alpine Valley c) The crater of question 14 d) The craterlets of question 17 e) The rille of question 21 f) The sinuous rilles of photograph B
RELATIVE DATING Determining the relative dates of two features is simplest when they are superimposed. The most recently formed feature modified the shape, structure or color of the older. One example is a more recent crustal fault cutting through a mountain range such as The Alpine Valley. Another example is an older crater filled with ejecta or maria lava. Rays are excellent indicators of age as they cover large regions of the Moon. If a crater is superimposed on top of the rays, it is younger than the crater from which the rays emanate. If the rays blanket the crater, the crater is the older feature. Further explanation is given at the beginning of the Mars Laboratory. By comparing the absolute ages of lunar rocks (as determined by radioactive analysis) with the relative dating of features from which these rocks came, a fairly thorough history of the Moon can be written.
8–6 27. By looking at the map, determine which of each pair is older. a) Copernicus / Mare Imbrium b) Archimedes / Mare Imbrium c) Cassini / Mare Imbrium d) Cassini / Cassini A
28. Arrange in order of age the following features seen in photograph B: the long, oval depression to the left; the small, round craters in the depression; the left sinuous rille; the maria whose edge can be seen in the photo.
8–7
WORKSHEET
8–8