About science; About the Moon
This is about science produced by the California Institute of Technology and originally broadcast by station KPCC in Pasadena California. The programs are made available to the station by national educational radio. This program is about the mone with host Dr. Peter less a man and his gas to Dr. Albert here. Here now is Dr. listen. A little. Rock to poets and physicists have in common. If your answer is a touch of lunacy you're right. At birth levels of meaning at least there are lunatics in the sense that they are both obsessed by the moon. For centuries that fear regent of the night has a roused man's fancies. What worlds of fantasy in a man to have been placed there by a man's imagination and what variety of views surely could the moon an orbit maiden with white fire laden with the wonderful touch of the McCarver and perhaps a more scientific intuition. Burton describe
Earth's only natural satellite as they RUIN IT world. A glow burnt out and a corpse upon the road of night. We're not scientists have taken over where the Perth left off. And the moon big in the live game for centuries is now big business and big signs and we're all involved with it. Lubbers librettists scientist songwriters poets and politicians all affected by her strange power. The scientists have found out that all that's green isn't cheese and not content with Mantas and they sent their own fancy machines up to the moon for a firsthand look. And what did they find. Rocks lots of them. The man of course has visited the moon yet but the sophisticated spacecraft sent aloft as explorers have done some impressive work. Our first craft to crash upon the surface of the moon was Ranger. It proved a spectacular success. Then came surveyor making a perfect soft
landing in returning thousands of detail excellent pictures of the rocky surface. Then there is the Lunar Orbiter. A small craft floating in orbit around the moon and making detailed maps of the surface. These photos from orbiter some taken from an altitude of only 25 miles above the surface reveal startling details of craters Highlands Mariya and some other very strange features. Here to discuss these questions with us now is Dr. Albert Speer senior staff scientist at Cal Tech Jet Propulsion Laboratory. Dr. Herd has been closely associated with all the efforts that sent robot explorers to the moon and is currently working in JPL for Advanced Studies Group. He is a county physics graduate obtaining his Ph.D. from the California Institute of Technology in 1950. Now that we have some background on what are the important questions that have to be answered. Well you know Peter I hate to reinforce the.
Similarly what you started out west but I believe that indeed the physicists in the poets do have something in common. The polarity of opinions which were expressed by your two quotations between me. The lively maiden in the dead burned out body are the poles of scientific opinion and I think still far despite what we've learned that is on the one hand the moon is an active body. There are volcanoes or earthquake something's going on down inside changes are occurring although perhaps too slowly for us to see. And the other is that no this is all done. The moon was active perhaps once when it had its early days a few leftover hunks of the solar system crashing into its surface but since then nothing. All that's left is the dusty debris of ancient explosions in spite of these wonderful pictures that you have out that I was so privileged to see we still don't know what's going on underneath there. No we really don't we do know that at least it's not like the Earth for example on
the earth we're familiar with a variety of types of earthquakes. And these leave their marks on the earth are easy to see. The San Andreas Fault is one of the most famous and not because it's so unusual because it's expose There are very few trees along its length and I would agree as we live on. Oh yes it's quite close to the centers of science which are concerned with its existence. And its slip sideways. You can clearly go out and see on the San Andreas Fault places where the the toes of of ranges of hills have been clipped away as the ground is slipped sideways. On the Moon there's a whole mass of these beautiful circular targets. Covering the surface almost totally. And yet not one of them is split in two. There's no no evidence whatsoever of a strike slip fault the sidewise falling as one example pretty clearly even up and down fall to vertical fall but none of the other type. So if there is internal activity in the moon that sort of thing that would show itself in stretching
or pulling of the crust of the surface. That activity is certainly different in the earth as the signs are not the same as those on the earth. So we don't see anything like the type of Earth Well we don't see the moon quakes not like a critic. That's one thing it's pretty clear that doesn't prove they don't exist but they're different so we have some explaining to do of course we have to admit we don't really understand why the earth quakes on the earth so the fact that we don't understand why they're not on the moon isn't too bad an example of ignorance. Well for that matter we haven't resolved what the poet cause the movie's pocked face we know it's quite true that's. Another result of the controversy on the one side are those who would say all of the marks we see on the moon the craters the little craters all of the marks in fact are the result of impacts one or the other one way or the other that are the result of impacts of meteorites big and small. And there are others who will say no not at all in fact a very few impact features almost all of them are the
results of volcanic activity either volcanic craters which would be rather small. Or something else called collapsed calderas which there are many on the earth and a very large crater like formations all over the thin trees in which we've been viewing the moon have we're going to notice a new marking on the face. No there was at one time something called the crater Linae. Which was observed by an astronomer before the days of photography and Ron in quite an quite great detail. And then nobody could see it thereafter so that was an example of a feature which apparently disappeared. It still hangs there as a controversy item. But we haven't seen anything form now that isn't too unusual if too is to realize that looking at the moon from here on the surface of the earth we have to look up through the turbulent atmosphere and everything in the sky that we see from here regardless of the telescope is smeared out the stars twinkle of course of the moon twinkles a little bit too and that's too bad so that the smallest
detail we can see from ours is several hundred yards across anything less is lost. Well since it's only been over fifty years now we've been photographing the moon. That means we've had a record of changes over the last 50 years of details which would have to be as big a several hundred yards across. Now if you go to the statistics of meteorites and ask how often is it likely that a meteorite would hit the moon to make that big a crater. It's in the order of thousands of years. Certainly not 50 years. So the fact we haven't seen any in the photographs is no indication that that is an impact because there could be an awful lot of small ones made all the time that are just lost in the fuzz. About radioactivity. There is no good indication of this. It's important for two reasons. First of course we believe the internal heat of the earth is radioactivity generated and that's what causes the. Eventually is the cause of the shaping of the crust of the earth and the continents the mountains and all that.
So the presence of radioactivity in the moon is an important part of understanding its internal behavior. There's another feature of it though the radioactive natural radioactivity of a few important elements helps to identify a rock. Uranium story of potassium and potassium 40 of these natural radioactive elements would be present in large extent in say a granite type rock not so much in a basketball type rock. So by sensing gamma radiation from these particular things you could make from a great distance hundreds of miles away rough chemical survey of the moon the Russians did this unfortunately with Luna 10 they had an orbiter called Luna 10 unfortunate their instrumentation was very poorly designed and the results were quite ambiguous. But they did indicate if you believe their data reduction that the moon was not granted it was said that no more radioactivity than bass although maybe less. On the other hand do we suspect that the moon is some earth like rock.
Well we do know. But up until a few months ago the green cheese would have still been a perfectly good assumption. Because all we had up until a few months ago were photographs and you just can't tell the difference between a hunk of cream cheese and Iraq with nothing but a photograph. But a few months ago we did put down the surveyor on the surface a small chemical analysis unit. In. Which analyze a surface by a very simple technique of bombarding it with artificial radiation and watching what bounce back. Now we have an analysis net and it looks very much like earthly best solved. Which is a common volcanic rock it exists in large plains in Oregon and Washington. Typical of the lava that comes out of the volcanoes in Hawaii. It's not the most common rock granite is a more common crust a rock but basalt is common common enough so we're familiar with it. You talk about the green cheese. I guess many old ideas have tumbled
in the last year. Yes I think so you see. This polarized opinion between the live moon the dead moon are expressed also in terms of what the surface is like. If it is a live moon and has been recently active then the surface would be covered with lava. Perhaps ash cinders but at least volcanic resolved the outpourings of volcanoes in one form or another. If however there has been no activity then the surface would be covered with the debris of broken up meteorites and as one scientist suggested some years ago these might be in the large dark areas. Seas of dust kilometers deep. He suggested at one time that a space ship could actually sink into the sink. Well these are the two ideas the two extreme ideas and I think that we. Have to some extent done away with the fluffy dust notion. It's not fluffy dust we can land on it. We can see the footprints of the surveyors that landed.
You may know one of them landed three times because it's a little over and your engines didn't shut off in time it kept bouncing across the moon like some huge beach ball. And we have seen with a little shovel we stuck into the surface we can measure the consistency so it's not fluffy dust but it is highly granular. So far there's no evidence of a flow of lava like you're familiar with from a volcano there's no solid lava in that sense at all. It could however be broken up lava. That is it could have once been many years ago a solid lava bed which meteorites have subsequently smashed up. That we can't tell yet. But it it's pretty clear however that the rock bass salt is the result of internal heating. So it's pretty clear that the moon has been in the past live. That's all has come out over the surface. And what we see now is. Chemically like Dassault. Physically it's granular so. So I guess there are many places on the earth that must be quite like the surface of the
moon. Well in a sense that's true of course the surface of the moon is a vacuum. There is no atmosphere. So in that way there is no place it's exactly like the surface of the earth because we do have water vapor and even the deserts the middle of the Sahara has more water than the moon. So in the in that sense the moon is not like the earth in the sense that it displays a chemical distribution similar to rock we're familiar with on Earth yes it is like the earth and of course as as you pointed out the photographs look quite like many of the earth. They do. They show this rather flat terrain out Lorraine if you like stretching off to the horizon set about a few rocks here and there. The rocks by the way caused great consternation when they were first observed to the dust people we sort of divide the groups into the dust man in the lab and then the dust men were concerned but
they they came up with a explanation. They rose to the occasion with something called instant rock. And this although it may sound like it's a frivolous notion it really isn't. Turns out that granular material can be compacted into rock like clumps by shock waves. So in an explosion even sand can be compacted into a rock of something like sandstone. So it's possible that even if. Even though there were rocks there they might have been the result of shock rather than the result of volcanoes. So the situation was still ambiguous even after the photographs of rocks were returned. However I get the dust out of the picture. Well certainly the notion that it's a fluffy dust layer deep fluffy dust layers out. I think that may have been pretty well out even before the surveyor landed you see. It's possible to do experiments with dust in a vacuum here on Earth and it turns out that the concept of dusting
us the feeling that something is dusty such as when you stick your hand into a flour sack and feel a dusting of the flour. That's really a property of air in the air between the particles of flour or dust lubricates the particles and allows them to slip. And so it feels dusty because the air is all gone. That same group of particles will tend to clump together and form a spongy but somewhat rigid mass. This has been demonstrated in a vacuum with all kinds of rock powders. So the fact that the granular material could support weight appeared to be clumping in places was no big surprise when we finally landed. So what you're saying is that death is a pretty odd concept in a vacuum with the belief that the kind of dust that we intuitively think of it as dust and just is hard to imagine exists in a vacuum and particles do tend to stick together. Well these discoveries that the that the program has made
work what are some of the things which we can deduce from them. Well for one thing we can certainly assert that as we've been talking about that the crust will support weight Now this was an important matter not only that will support weight but how much because after all the major effort of the lunar program is to land a man and we had to have some reason to believe that the landing craft which would carry him to the surface would support itself when it got there and then after the man got out that he would be able to walk around without sinking need deep. And that's clear that it's perfectly safe both for the craft in the manse and one thing this is true practically everywhere on everywhere we've landed we've landed five surveyors have landed out of the series of seven remarkable engineering achievement by the way we anticipated we'd be lucky if we got two of them to work that well although I don't want to put down he engineers are working out of that magnificent job. And everywhere we've landed it's the same the same type of crustal
material the same granular material in about the same bearing strength. Also one of the other objectives. Which we had throughout the program from the ranger program on was to make sure the areas were smooth enough. And as I mentioned a moment ago the view from the earth is so fuzzy that it's impossible to tell whether or not the surface in detail may be covered with craggy rocks sticking up huge Kra vassals crisscrossing the surface there's no way of knowing that from here. We actually had to go there and look close up. The Rangers looked in three different areas and saw some of the surface. They couldn't tell what it was like because they crashed they just took pictures on the way and when the surveyors landed of course they saw the same general smooth surface as the Rangers but they then could see it in more details what it was made of and land on it. So the fact that there area smooth enough for landing is also very thoroughly established. And then the. The general picture of the surface is one which was
somewhat surprising even at the beginning. The Rangers which photographed the surface in detail. Did not show in fine detail a mass of small craters all overlap each other. How do you think of the pictures of the moon you've seen the central portion where most of the craters are called the Highlands. These craters ripped all piled on top of the other Everyone is breaking into the rim of its neighbor and just one on top of the other. When you look now and closer and closer into finer and finer detail till you're down looking at craters it may be a hundred feet across fifty feet across ten feet across not like that at all they're all quite separate. Very few of them overlap each other. In fact they're rather scattered about without much connection at all. Now this is a as I say was a surprising discovery and it implies that somehow craters are being filled in. That there is an erosion process on the moon because these craters must be formed at a fast rate. We know that there is.
We know the distribution of sizes of meteorites so we know that there's enough meteorites to form little craters so that if nothing happened to them we would have seen a field of small craters all overlapping each other one crater right on top of another. The fact that that doesn't exist implies it somehow rather the surface of the moon is getting smoothed over a little bit faster than craters are getting made. That's a very surprising thing since this new window air was good. It is indeed and there's a number of ideas have been proposed to account for this. One of them is that simply the bombardment of very little particles of the microscopic size or millimeter sized particles keeps kicking up stuff and scattering it about and so material is continually redistributed and redistributed mixed up with a kind of space then blasting. Yes that would be the idea. And in fact it's even more like space like sandblasting that there is one idea that the moon in its present condition is losing more material
by impact than it gains. The explosion which takes place when an impact hits is strong enough to remove more than the weight of the incoming body. Rather interesting idea is the fact what happens to it goes out into space and perhaps some of it comes down here on the earth. Some of the meteorites we pick up here on the surface of the earth may well be samples that were blocked blasted off the moon a few million years before and swinging in orbit until they finally hit here. That's a fascinating subject. What about some of the some of the earth's famous meteorites that are thought to be part of the. Well there is one group that was suggested by Michael do can lease over Caltex several months ago as a likely candidates for a lunar origin there a particular kind of meteorite called the basaltic a cond rights that's the name for them is because they're like bass Alton because they're not conned right so they're a kind writes cond right as a most common type of meteorites a kind of meteorite that has little apparently little
bead like in inclusions in it and these do not. There are the many characteristics of these which are interesting and they they show from there and you crack them open look at their insides that they're. There the result of rocks that have been reworked many times Brescia that's been the result of something some precursor that was broken up then reformed re compressed into a new rock perhaps broken up again the pieces again re compressed and so many workings over between the time that the crystals were formed out of some melted body and the time that we now look at the solid rock. Many things have happened to it the last of which of course that it was knocked away from wherever it was formed and flew through space to the earth. Now they're a little bit different than most bass salt on the earth they're called a Salt Lake but there is a few important differences for one thing. They have slightly more iron in them than Dassault on earth. It's a small difference but it's significant.
Well it turns out that the chemical analysis of the surface of the moon indicates that although the moon is like earthly bass all it too has slightly more iron than a typical bass out of the earth. So the old theory of not too old about a year old theory of. Do can so over. Based purely on arguments of the what would a body have to be like in order to produce the kind of rock that we now find in these meteorites that's how they started their argument. And went through an argument like that on that basis they said Well Ramon is a good candidate and now we go up and measure the chemistry of the moon and it's quite exciting to discover that these two men picked out a very good candidate because the chemistry matches beautifully. There it is. And I guess though they know they're meteorites because they appear in a place where they didn't know to be. Well if they were seen falling Oh they're meteorites are generally divided into two classes falls and finds the falls are the ones that somebody actually sees coming out through the
sky and goes out and picks up these are the rare ones. The finds are the ones that you the geologist walking through the field notices an odd rock and picks it up as a Hudson meteorite. As you can imagine with these basaltic who a contract's are not likely to be fines because they look too much like Earth rocks and. It would be quite accidental for somebody to discover that most of the find meteorites are the irons which are an iron meteorite is quite an obvious thing it's a hunk of iron it's got all kinds of funny holes in it usually that's obvious so that among the fines the irons are communist but these are Falls. So they're genuine guaranteed meteorites. And then when you pick them up and look at them it's quite clear to their cover of the black crust formed when they entered the earth's atmosphere. So they've had their own re-entry and the place and they have indeed. How often does are these fines.
I really don't know the statistics of this speed. I know that the Among the fines. As I say these represent about 5 percent but I don't know how often it happens and some odd stories about people who find meteorites and then take them around to various universities looking for the highest bidder. Yes I couldn't imagine and I could also imagine that this frequently with the being described in the Bible and disposed of by Victorian rationalist think it's a bit of myth and not only Victorian rationalist thinkers. In the days of the birth of our country it was not considered quite right to believe in meteorites. And Thomas Jefferson as a matter of fact received a note from two professors at Harvard about a meteorite they had seen fall and his response was I would rather believe two Yankee professors would lie than the Stones would fall from heaven. That's when the fourth.
Well Mary what about some of the questions still to be unsaid. You know I was. Gazing through some Cretaceous about the moon I happened to observe that Shakespeare was one of these modest touches of intuition described as watery. Now how about that. Well I suppose he was representing in those days. The picture that was held around the time of Galileo and shortly thereafter. That large dark areas on the moons were oceans. In fact that's how that's what they're named the Marree which is Latin for see and have beautiful names tranquil Tatis and serenity goddess and so on. And so many people in those days believe the moons had Ocean but now we know there's a vacuum. And everybody is content to believe there is no water on the moon as I have reported to you it's drier than the Sahara and yet some of the orbiter pictures have shown things which are most surprising. These are again details that you could not see from Earth and some of these details look
compellingly like River Valleys. And this is a very difficult thing to understand. Now the reason the moon doesn't have an atmosphere is because of its low gravity it can't hold on to the molecules molecules get heated up in the sun and go bouncing around that bounce enough to take off forever. The earth has enough gravity so the molecules can't bounce away so easily. But it takes more time it takes a little while for the molecules if the moon had atmosphere for example that if somehow or other you could suddenly give the moon an atmosphere it would take a few hundred thousand years for it to leave. Now that's smaller than the life of the universe. The life of the solar system say around 5 billion years a few hundred thousand years a blink of an eyes so the moon could never hold an atmosphere for that length for the life of the solar system but suppose suppose a comet were to hit the moon. Well I know many people who believe that comets are the cores of comets are made primarily of ice. And if this were true then a comet hit the moon. The heat would
undoubtedly evaporate the results and might some of it might stay around in the form of a temporary atmosphere. And under such a temporary happiness fear there might indeed at one time have been water on the surface which would last for a short time but perhaps long enough to cut river chattels That's one theory at least. Really Old Dry River could run as well it's one idea it's not the only one the other one is that it's formed by flowing ash from a volcano this happens on Earth. Ash mixed with gas will slow the gas bubbling through the ash makes it behave almost like a liquid. And this too would perhaps act to erode away and cut a river valley if it were such a thing. So these features are so new. And there's only a few of them that have been observed in a few or better photographs and I think that it's quite understandable that a certain amount of controversy now exists about their origin.
But people are not quite as certain as they once were when they say that there's no water on the moon. Well it's true they're not know at least I think they're certain when they say there's no water on the surface now. But now there's other ideas if there was water once in the past or if well after all the moon had to be made out of something and water. Should be the commonest molecule in the. In the universe hydrogen and oxygen being among the commonest elements. So it's possible that the in the early days of the moon a lot of water was included in it and some of this may still be there because the moon's surface is a very good insulator. This was about science with host Dr. Peter lissome and his guest Dr. Albert hips join us again for our next program when two more prominent scientists will discuss the subject of general interest about science is produced by the California Institute of Technology and is originally broadcast by station KPCC in Pasadena California. The programs are
- About science
- About the Moon
- Producing Organization
- California Institute of Technology
- KPCC-FM (Radio station : Pasadena, Calif.)
- Contributing Organization
- University of Maryland (College Park, Maryland)
- AAPB ID
- Episode Description
- This program focuses on scientific study of the Moon. The guest for this program is Dr. Albert Hibbs, California Institute of Technology.
- Other Description
- Interview series on variety of science-related subjects, produced by the California Institute of Technology. Features three Cal Tech faculty members: Dr. Peter Lissaman, Dr. Albert R. Hibbs, and Dr. Robert Meghreblian.
- Broadcast Date
- Media type
Guest: Hibbs, Albert R.
Host: Hibbs, Albert R.
Producing Organization: California Institute of Technology
Producing Organization: KPCC-FM (Radio station : Pasadena, Calif.)
- AAPB Contributor Holdings
University of Maryland
Identifier: 66-40-79 (National Association of Educational Broadcasters)
Format: 1/4 inch audio tape
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- MLA: “About science; About the Moon.” 1968-03-10. University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Web. October 16, 2021. <http://americanarchive.org/catalog/cpb-aacip-500-6h4csg57>.
- APA: About science; About the Moon. Boston, MA: University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Retrieved from http://americanarchive.org/catalog/cpb-aacip-500-6h4csg57