Apollo 16 Mission
Landing Site Overview
"The LM landed in a subdued old crater, approximately 75 meters in diameter. In general, the landing area is saturated with these old craters so that the few young sharp-rimmed craters provide a notable contrast to the pervasiveness of the old craters. In the immediate vicinity of the LM, a few 1- to 2-meter craters have glass-coated bottoms. This glass is cracked and wrinkled so that it looks like dried mud. A low percentage of the surface is covered by subrounded to subangular blocks. To the north, the Turtle Mountain ridge shields the traverse route of the third period of the extravehicular activity. To the south, except between the many 5- to 10-meter ridges, we could see the EVA 2 traverse route as far as station 4. The surface sloped to the south an estimated 100 meters, where a gentle rise marked the beginning of Stone Mountain."
John Young, Thomas Mattingly, and Charles Duke
Landing Site Selection
The Apollo 16 landing site was selected to obtain samples of two highland geologic units, the Descartes Formation and the Cayley Formation, which are widespread on the lunar nearside. Prior to the mission, it was thought that both were of volcanic origin, but the returned samples demonstrated that this is incorrect.
Three of the first four Apollo Moon landings were in mare regions and the fourth was in ejecta from the Imbrium impact. When selecting the Apollo 16 landing site, the highest priority was given to landing at a site in the lunar highlands, which occupy more than five times the surface area occupied by mare units.
Two locations were given primary consideration, the Descartes region west of Mare Nectaris and Alphonsus crater. In Descartes, the objectives were to sample the Descartes Formation and the Cayley Formation. Based on the interpretations of telescopic and orbital imagery, it was thought that both units were volcanic in origin, although formed of magmas that were more viscous than mare lavas. Samples obtained by Apollo 16 proved that these units are actually breccias produced by impacts rather than volcanic features. From the density of impact craters, the Cayley Formation was thought to be comparable in age to the Imbrium impact. These premission geologic studies suggested that these two formations covered about 11% of the lunar nearside, making them important for the overall understanding of the Moon's history. Also, the large distance between the Descartes site and previous landing sites was helpful for the network of geophysical instruments created by the Apollo 12 through 16 missions.
There were three sampling objectives for the Alphonsus crater site: the crater fill itself, possible pre-Imbrium material from the crater wall, and possible young volcanics at some so-called dark halo craters on the floor of Alphonsus. However, some geologists felt that the Alphonsus site had been contaminated by ejecta from the Imbrium Basin impact. Also, at the time the Apollo 16 landing site was selected in June 1971, the Apollo 14 samples had been incompletely analyzed and the Apollo 15 samples had not yet been obtained. It was considered possible that the objective of obtaining samples of old highland material (older than the Imbrium impact) might be met with some of the Apollo 14 or 15 samples.
Accordingly, it was decided that Descartes would be the landing site for Apollo 16. The Alphonsus site was considered at the time to be the primary candidate for the Apollo 17 landing site, although this was later rejected. The Descartes site was certified as safe for landing on the basis of Apollo 14 orbital photography. The specific landing site was selected between two fresh, young impact craters, North Ray Crater (1000 meters in diameter) and South Ray Crater (680 meters in diameter). These craters provided natural drill holes through the regolith at the site, exposing samples of the underlying bedrock in ejecta fragments for sampling by the Apollo 16 crew.
Orbital Views of the Landing Site
Stereoscopic Views of the Landing Site
The Apollo 16 landing site (green cross) is on the relatively smooth Cayley Plains, between the two bright ray craters in the center of the stereo pair. The Cayley Plains extend to the west of the rugged Descartes Mountains in the center right and bottom of the scene. These views (portions of Mapping Camera frames AS16-974 and AS16-976) measure ~65 kilometers from top to bottom. North is to the top. This stereo pair has a vertical exaggeration of about 3. Topographic relief across this scene is about 900 meters.
Red/Green (Anaglyph) Images
To view anaglyph stereo pairs you need red-green (or red-blue) stereo glasses. These glasses have a red lens over the left eye and green (or blue) lens over the right eye.
Black and White Images
To view side-by-side stereo pairs, use pocket stereo viewers (obtainable from local educational suppliers, bookstores, etc.).
Side-by-side stereo pairs can also be viewed with the unaided eye by focusing on each image separately and allowing the eyes to cross. If you wear glasses, it may be necessary to remove them and view the pairs from 6 to 10 inches away. These techniques may require some practice (the Apollo 15, 16 and 17 stereo pairs are good for this purpose). Another means of assisting this process is to place an index card upright between the two images, forcing each eye to see the different images. Only approximately 10% of the general public cannot view images stereoscopically.
Surface Views of the Landing Site
|Looking North from the Apollo 16 Landing Site|
|Looking East from the Apollo 16 Landing Site|
|Looking South from the Apollo 16 Landing Site|
|Looking West from the Apollo 16 Landing Site|
For more information:
Clementine Views of the Apollo 16 Landing Site
Images obtained in 1994 by the Clementine spacecraft provide information about the composition of the rocks in the vicinity of the Apollo 16 landing site.