Most students of the moon favor the latter possibility. The debate centers on what the mechanism might have been. Several mechanisms have been proposed: the filling of a low-density, fragmented lunar crust with lava; a flow of lava into an impact crater; the upwelling of denser material from the lunar depths into giant impact basins; even the deposition of sediment in the maria by flowing water that later dried up. The last hypothesis carries the intriguing implication that water not only existed on the moon at one time but also played an important role in lunar history. In any case, the analysis of samples from the moon takes on added significance as a result of the mascon phenomenon. An exciting result from the preliminary measurements of Apollo 11 samples is that their density of 3.2 to 3.4 grams per cubic centimeter, which would be high for terrestrial rocks, may be related to the existence of the mascons.
Sites for Exploration
The present plan of the National Aeronautics and Space Administration is to make nine more manned explorations of the moon over the next three or four years. The sites for the first few will probably be determined on the basis of constraints similar to those that were in effect for the Apollo 11 mission, namely that a landing place must be on the side of the moon facing the earth, so that constant radio communication can be maintained between the earth and the landing party; that the site be in a region free of obstacles, and that it be accessible from a free-return orbit, meaning an orbit that will enable the astronauts to return to the earth with a minimum of power if the main engine in the command module should fail. These constraints restrict the next few landings to mare sites near the lunar equator.
Later it should be possible to venture farther afield and to land at or near other sites of particular scientific interest. A number of places are under discussion as possibilities for these landings, Instead of describing them all, we shall focus on four candidate sites and a long-traverse area that we believe offer significant clues for deciphering lunar history. No particular significance should be attached to the order in which we discuss the sites.
The first site is the small, extremely fresh crater Censorinus, A landing here could be expected to achieve three objectives: to establish the age of what is clearly a very young feature on the lunar surface, to investigate and characterize an unquestioned impact feature and to obtain samples of material from a region in the highlands, An alternative site, which would offer similar possibilities, is the crater Mosting C.
The second site represents the much more ambitious goal of exploring one of the major craters. Such a crater is Copernicus, which is about 70 kilometers in diameter and has prominent central peaks within it. The ejecta from this relatively young crater cover more than a tenth of the front face of the moon. The relief within the crater is more than 15,000 feet [4,572 meters], making it comparable to the most mountainous areas on the earth. An alternative site, with quite similar characteristics, is the crater Tycho. These large craters are of interest not only because they represent major events in the history of the moon but also because, by analogy with much smaller terrestrial craters, they should expose material from a range of depths up to 10 kilometers, and perhaps even more. It has been suggested that the central peaks in these craters may consist of material now at the surface that has come from depths of 10 to 15 kilometers or more. Thus, even though the material in a crater may be jumbled, broken and deformed by shock processes, it should provide a diverse sample of the outer few kilometers of the moon and a basis for interpreting its history.
Third, we point to the extremely interesting Marius Hills region. It is one of several areas where constructional features such as domes and built-up cones are more numerous than craters of a comparable size. The region is also associated with one of the longest lunar ridge systems, which crosses a large expanse of Oceanus Procellarum on the western half of the moon. The tectonic setting of the region is similar to that of terrestrial volcanic fields such as Iceland and the Azores. The setting and structure of the Marius Hills region suggest that it is an area of volcanic activity where igneous material has been added to the surface through vents.
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5 Comments
Add CommentThe Apollo missions were truly 50 years ahead of their time. 50 years societally & technologically. We ought still to look back at what our ancestors achieved, with the resources at hand, and the will in mind, in awe.
Reply | Report Abuse | Link to thisI disagree hotblack, the Apollo missions were 7-10 behind the times. If Wernher von Braun was given the opportunity earlier, we would have gotten to the moon by 1959-62. The German scientist was way beyond his time. In one word "Brilliant". Why doesn't Nasa have any of these guys around?
Reply | Report Abuse | Link to thisPerhaps technology. But Werner Von Braun as a Nazi was societally 1000s of years behind. Better to not have achieved the moon landing and other technological goals than be a Nazi
Reply | Report Abuse | Link to thisdoron, surely you must be aware that Von Braun was a reluctant Nazi. He earned the enmity of his superiors on several occasions because of his outspoken vision of rocket-enabled space travel and exploration, rather than rocket-enabled world domination. Von Braun was not enthusiastic about the Nazis or the war. This characteristic almost cost him his life. Viewing the past through the lense of the present affords many opportunities to wax morally superior to one's ancestors. The moon landings were a culmination of Von Braun's inspired vision of human progress, and had nothing to do with the Nazi Party. Perhaps you had better get your own house in order, doron - before you ask the entire human race to discard any dreams of reaching beyond, for fear of disturbing a tree or a slumbering faun.
Reply | Report Abuse | Link to thishotblack - Do you know how much I despise those who state that "so-and-so was ahead of their time" simply because the ball got dropped later on? Apollo was firmly of its time. The moon mission could have been completed earlier than 1969 had it not been for delays. Saying that Apollo was 50 years ahead of its time is the same as saying its OK that we're currently doing nothing of consequence in space. I vehemently disagree with this state of affairs. I will add, hotblack, that using your logic, Apollo wasn't just 50 years ahead of its time. If the Chinese make it to the moon by 2020, Apollo will be officially 61 years ahead of its time. If you ignore the Chinese and just count NASA, well... you might have to wait a pretty long time to find out. They'll probably not go their again. We entered our long decline a while back.
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