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Oral History Transcript — Dr. Eugene Shoemaker

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Interview with Dr. Eugene Shoemaker
By Ron Doel
At US Geological Survey, Flagstaff, Arizona
June 17, 1987

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Eugene Shoemaker; June 17, 1987

ABSTRACT: Early career in the United States Geological Survey (USGS); Atomic Energy Commission-sponsored surveys of uranium deposits in the western United States; USGS Grand Junction, Colorado field office; nuclear explosion crater studies; the MICE project; early lunar studies sponsored by NASA. Specific topics include Shoemaker’s investigations of the geology of the Colorado plateau; doctoral studies at Princeton University in the mid-1950s; his identification of coesite at the Meteor Crater, Arizona; and the Ries formation in Bavaria, Germany; the development of lunar stratigraphic principles.

Transcript

Session I | Session II | Session III | Session IV

Doel:

At the end of our last interview, we were talking about the beginnings of your contacts with astronomers who were concerned with doing planetary observations. It was in the late 1950s, was it not, that you first became acquainted directly with work being done by Gerard Kuiper of the Yerkes McDonald Observatory?

Shoemaker:

Yes, it was. Actually, at about the time that I began the work on the MICE Project, I had been tracking the state of the art development of the ballistic missiles and ballistic missile program, because I figured that's how the United States was going to get into space. So I subscribed to a journal called MISSILES AND ROCKETS just to kind of keep my finger on it, and I could see that, from my perspective, things were starting to get hot. It looked to me like we were going to have a space program, although the ultimate way in which this came about was of course quite a surprise. And so when I was on a trip to Washington at one stage, I made it a point to go in and see the director of the Geological Survey.

Doel:

Was that Thomas Nolan?

Shoemaker:

That was Thomas B. Nolan, yes. I just decided I'd go and see if there was going to be a chance to do something about what I saw coming down the pike. Of course, I was one of those crazy few people who thought in these terms. It certainly wasn't an idea current among any of my colleagues on the Geological Survey, that I was aware of. So about 1956, I've forgotten the exact date, I was in Washington, so I went in to see Nolan and I told him what was on my mind, that I thought that there would be a program of space exploration that would evolve, a capability of sending objects into space. Of course, I didn't guess how fast it would come. That caught me by surprise. I could see it was coming, and at that time I was engaged in field work in the Hopi Buttes in Arizona, and I was also pursuing studies of nuclear craters, and had a look at the Meteor Crater and was planning to undertake a detailed study of that as well, at about that time. So I told Nolan what I hoped to do was, when I had completed a fairly major program I had scheduled in the Hopi Buttes, I was hoping that it might be possible to start a very modest program of geological study of the moon. I had actually had in mind about a four man project to work at the telescope, with telescopic observations and using available telescopic photographs, and try to start some systematic geological mapping. And I think it's a great credit to Tom Nolan that he took this proposal quite seriously. There would have been rather few men in the Geological Survey who would have. Well, bear in mind this was pre-Sputnik. Nobody had put a satellite even into space yet. And so this was a rather strange idea to come from a rather brash young man, although I had met Nolan in the field. He knew who I was. I had met him in the field in Nevada earlier.

Doel:

He'd just been appointed director.

Shoemaker:

He had rather shortly before become director, that's true. I had spent a summer with James Gilluly in central Nevada, and Gilluly and Nolan were old buddies and actually old classmates at Yale University, so we'd gone over to see Nolan's field area in the Eureka district, while I was there in the summer, after I was married to Carolyn, so it was in the early fifties. I had met Nolan but I didn't really know him very well. Well, actually Nolan took the whole thing quite seriously and he sent me to see Bill Ruby, who was sort of the chief scientific advisor to the director at that time, and Bill Ruby took it quite seriously too. I wasn't pressing of course to start something right away. I really had in mind something that would happen in maybe four or five years, at that point in time. I was just trying to lay the groundwork for it. But I was concerned, I thought maybe there are some other visionaries, who knows? Maybe in the Department of Defense there were some guys secretly working away on the moon that I didn't know about. And so Ruby in fact undertook to make some inquiries for me, to see if any classified work was going on that might represent something comparable that was already happening. He checked into that and found out there wasn't at that time. Interestingly enough, not long afterward, some efforts were started by the US Army Corps of Engineers, but this was still before that, and another interesting thing was, there were two topographic engineers in the topographic division who'd also been thinking about the moon, not about the geology, but they'd start thinking about, well, I wonder if we could map the topography of the moon? And had actually sat down and taken a serious look at it. I regret to this day that I didn't really get together with them and get something started then.

Doel:

Who were they?

Shoemaker:

You know, the names have gone by. It would take some real digging to find out. It's been so long, I've forgotten the names. But I did find out about that, too. So I went right to the top of the Geological Survey, and the thing was taken quite seriously. I think it was a good thing that I did that, because I kind of set the idea in motion with Nolan, and Nolan was a very strong supporter later on then when we finally did really get a project started, and there was a little bit of tradition, interestingly enough, I think that helped that, because G.K. Gilbert had done this famous study of the moon when he was the chief geologist back in the 1890s, so he'd set a little precedent for me. So that was probably a help. But as I look back on it, I think it's really quite remarkable that Nolan was as receptive as he was to this idea, and he played an important role later in negotiating with Homer Newell and NASA an agreement with regard to the Survey's participation in the whole moon program. So that was kind of the beginning. I finally, I came out of the closet in 1956 and decided to cast away my secret cloak, the cloak covering my secret ambitions and come out in the open and really start to push it, because it looked like things were going to happen at that stage.

Doel:

You mentioned a moment ago not only examining the lunar photographs which had already been made, but doing additional telescopic observations. Did you have certain observatories in mind? Had you already been corresponding?

Shoemaker:

Well, I knew that Kuiper was working on the moon. As I told you, I had some papers of Kuiper's at that time. It's an interesting fact that some of the very best photographs, the best photographs that were available that had been taken of the moon at that time had been taken with the 100 inch telescope on Mt. Wilson, and they were taken in the early years, the first five years or so after the Hooker Telescope was put into operation, and so when they had an especially fine night of seeing, and the moon was in an appropriate phase, they'd take some plates of the moon with the 100 inch telescope from Mt. Wilson, I think mainly just to brag on the optics and the site more than anything else, but F.G. Pease had taken these photographs in early stages, and they were available. They had a nice selection of the best photographs. You could purchase them at the Caltech Book Store, so I had a set of these photographs. I didn't of course have an extensive knowledge of other sets of photographic data available at that time. And Kuiper, a few years later, really started a systematic effort to collect the best photographs available world-wide, to compile an atlas for the US Air Force. So I had these photographs, but I knew that in order to be able to do the kind of geological study I was thinking about, it would be crucial to go to the telescope and go eyeball to eyeball with the moon, the reason simply being that astronomical seeing usually degrades the photograph so much that really most of them are not terribly useful, and you need the finest details you can get to try to work out tricky problems like the stratigraphic sequence of the deposits. So I knew that direct visual telescopic observation would be essential, really 19th century science. The reason was simply that nights of very good seeing, with the human eye, you could resolve features actually about a quarter the size of the best things that could be resolved in the available photographs, and that's a very important gain.

Doel:

Were you making sketches at the telescope?

Shoemaker:

No, not really. I wasn't sketching. What we were trying to do was to determine sequence, and one of the key features in determining sequence has to do with the craters, and the crux of it was to be able to know what the age relationships of craters were. Well, for the largest craters, you can see a swarm of very tiny craters surrounding them, which I called secondary craters, I'm probably not the first one to call them that but that was the term that I used, and they're clearly related to the main crater, the primary, and in fact are produced by ejecta thrown out of the primary crater. And if one can resolve the secondary craters, you know that when you see secondary superimposed on some other element of the lunar terrain that the primary crater with which they are associated must be younger than those other trails, those other geological units. So one of the really key things we were looking at was to resolve secondary craters, and you could only resolve secondary craters around a few of the large craters in existing telescopic photographs, but with the telescope you could see them. So we were looking for very very fine details that were crucial features to enable us to unravel the lunar stratigraphy, by that technique, and there's more looking for — sometimes we would have details, and we'd look for specific — we'd study the photographs, the best photographs we could get, as carefully as we could, and frame a series of hypotheses about what the stratigraphic and structural relationships were. Then you'd go to the telescope to check them.

Doel:

Was Copernicus your first choice?

Shoemaker:

Well, Copernicus was an obvious choice because, first of all, it's relatively near the sub-earth face of the moon. The center, it's relatively near the sub-earth center of the moon. And it's a relatively young crater, with a very nicely portrayed ray system, which crosses over a wide variety of different terrains, some of which have fairly large contract in the photometric properties, with the rays of Copernicus, so you really could work the relationships out very well, and it's a big enough crater, it's 90 kilometers in diameter, you could see lots of the critical features of Copernicus, so it just was an especially convenient part of the moon to study. And it was beautifully photographed in one of these very best photographs with the 100 inch telescope. I had a superb photograph in which Copernicus was the right distance from the terminator for one to see these details.

Doel:

That was another Pease photograph.

Shoemaker:

That was a Pease photograph, right. So that's why I started with Copernicus. It was in the best position and we had an exceptionally superb photograph for it. One could look at other parts of the moon, but that was the reason. So I was in fact looking for opportunities to get to the telescope, and one needed to get to large telescopes, and Kuiper had described features that he had seen visually at the McDonald telescope that no one else had ever seen, and it seemed a good place to go, and that's why I sought Kuiper out, to learn more about that myself and also establish some contacts there. At that time, the leading person, certainly in the United States and I think one could say probably in the world, who had an interest, a similar interest in the moon — after all, the moon had become passe for astronomy generally. Kuiper was one of the few distinguished astronomers who had maintained a strong interest in the solar system. So he was the logical person to get to know.

Doel:

What were your impressions of Kuiper?

Shoemaker:

Well, somewhat to my amusement, certainly, he was very much a European, having been born and raised and academically trained in the Netherlands, so he had a little different view of the world than American academics do. In his background, he was more the European professor. But he was very congenial, very cordial, and of course there were so few people interested in the moon, I think he was delighted to find other people who shared his interests, so he was really quite hospitable, and I did visit him at Yerkes Observatory, very early on, in the late 1950s.

Doel:

You presented a colloquium there, I believe.

Shoemaker:

I don't know whether I gave a seminar there or not. I don't recall. I was — I did get involved later on in Southern California with what was called the Lunar and Planetary Colloquium. But really this is before I had done much serious work. I don't think so. First time I saw Kuiper, I don't think I went to give a talk or anything. I just went to get acquainted with him at that stage. I hadn't done enough work yet myself to have something to talk about.

Doel:

This was in the early 1950s?

Shoemaker:

No, this would have been mid-fifties. I think the first time I made contact with Kuiper must have been somewhere around 1956 or '57. I don't recall the date. 1957. Well, all of that was rather preliminary actually. I was just exploring the ground, and wasn't thinking that there was a particular rush at that point in time, because I really anticipated that nothing much would happen before about, oh, 1960 or thereabouts, was kind of my target date, and I had just — I got back to the field. We were working in the late fall, as a matter of fact, in the Hopi Buttes in 1957. I had a field camp set up there, and two other men were working with me, Carl Roach and Frank Byers, and I had Carolyn and the family with me in the field. My youngest daughter was just a tiny baby at that time. I got back from a MICE Project meeting at Oak Ridge, I'd flown directly back to go to the field, and drove back out into the Hopi Buttes, and Carl and Frank had a radio out with them in the field, and I got into camp fairly late, and I think it was Carl said, "Guess what? The Russians have launched a satellite!" And my immediate reaction is, "Oh no! I'm not ready yet! It's too soon." All this work I was planning to do in the Hopi Buttes. But I knew, as soon as I heard that, that the fat was in the fire. And I had begun exploring things seriously about a year earlier. So I never did finish the work on the Hopi Buttes. The following year, the Geological Survey office in Grand Junction was closed, since the whole uranium exploration had been shut down. Most of the people were transferred to the Denver center.

Doel:

Had that happened because the amount of uranium which became available was sufficient to meet United States needs?

Shoemaker:

Yes. The immediate needs of the United States were suddenly going to be fully taken care of with new discoveries. So the three of us went to Menlo Park, California, from Grand Junction, all of us dyed in the wool Californians, or at least we were not interested in going to Denver. That turned out to be a fortunate choice in any event. The rest went to Denver. And California was a good spot to be located at the dawn of the space age. Of course, there wasn't anything I had to do immediately, but at about that time, as soon as Sputnik broke the ice, a lot of people suddenly started to get into high gear, and after I got back to Menlo Park, I got a call one day from Monty Klepper who was the assistant director — because people then knew I was interested in this, and the Survey had been getting some inquiries about doing lunar research, and in fact one of these came from a very interesting man by the name of John O'Keefe who was at that time still working for the Army Map Service as a geodicist, his training, in fact, he was from the University of Chicago, had been a PhD student at the time that Kuiper was there, and O'Keefe was interested in getting some research going on the moon, but he was still at the Corps of Engineers at the time, and he arranged — quite independently, I only found out about it after the fact — for a contract to be let from the Corps of Engineers to the military geology branch of the Geological Survey, to undertake a preliminary study of the moon.

Doel:

This was also intended to be a topographic study?

Shoemaker:

No, it was intended to be a geological study, and so — in fact military geology took that on. Then I found out about it later. So I got immediately in touch with these people, and the person who did the study or supervised it in the military geology branch was a man by the name of Arnold Mason. The Geological Survey had a program of support to the Defense Department intelligence services, something that grew out of work during World War II, providing geological input for terrain assessments for sort of basic systematic studies of the world on a country by country basis, of military traffic-ability and the various components, geological things that had to do with understanding military operations. And so that's how there was a connection between the Geological Survey and the military. That's why the connection came through military geology at that time.

Doel:

How large was that branch in relation to the Survey as a whole?

Shoemaker:

Oh gosh. I think at that time there might have been about 20 geologists. Maybe it was a little bit bigger. It might have been 30 in the branch, about 30 people. Well, so I got a study started there, and it was funded out of DOD, not out of NASA. That really got started before NASA was in business. NASA didn't get organized until 1958. And they were just kind of putting their program together at that time. Later on O'Keefe did transfer then from the Army Corps of Engineers to NASA, to the Goddard Center. So there was an effort started there, and I did some scouting around and talking to people on the West Coast, for military geology, as a part of the effort, and I started going to the Lunar and Planetary Colloquium, which was organized by a group of people mainly with aircraft companies but also at JPL and Rand, around the Los Angeles area. People were getting excited about space exploration, and of course the nearest place you could get to beyond the earth was the moon, and people were thinking about the moon, and so there was this rather informal group that sprang up that was in part supported by funds from North American and other airframe manufacturers in Southern California, to start to probe and explore the kind of science one might be interested in in going out into space. So I participated in that, and meantime, I started thinking seriously about how to get a Geological Survey program going, and Monty Klepper called and I've forgotten what happened, how it got stimulated, but he had some inquiries from the outside at that time, and I thought, well, maybe we ought to see who in the Geological Survey might be interested in getting into lunar work.

Doel:

This is still the late 1950s.

Shoemaker:

This is 1958. Yes. And so, we had a meeting. We tried to call a meeting and circulated a memo around, that anybody who would be interested in engaging in scientific studies connected with lunar exploration in particular was invited to come.

Doel:

Throughout the entire US Geological Survey?

Shoemaker:

Well, as the meeting was held in Washington, it was really only people in Washington, besides myself, that were keen to do this. There were about a dozen people that showed up. None of them really had been thinking about the problem as seriously and in the same way that I had. But we did determine that there was an interest, and so I went back out to Menlo Park and tried to set down my ideas on a program. And I wrote this up and circulated it, the main elements in the program being to first begin a geological mapping study, then there were a number of other ideas had been put in the pot at that time, mainly how to study the moon.

Doel:

The stratigraphic program.

Shoemaker:

Well, the stratigraphic program was my idea. You know, I can't really recall at this stage all of the other suggestions, and none of them were very strong. One of them was a continuation study of craters, how the craters formed, and this was kind of evolving out of my own work as well. So Bill Fischer, who had sort of started the photogeology group within the Geological Survey, was one of those who had an interest, and so he had some specific ideas on how one would proceed working with lunar photographs, and probably had the most useful input at that time, outside of the things I put into this myself. So we circulated this memo, and then ultimately ended up drafting a kind of a program that might be taken over to this new agency that had just been formed, which was NASA. So by late 1958, we had a concrete proposal that was placed on the desk of the new chief geologist who had come in by the name of Charles Anderson. Anderson was an economic geologist, and this was just at the time in which the geologic division in fact was in very considerable turmoil, because of the cutback in the AEC funded effort.

Doel:

Which had closed the Grand Junction station?

Shoemaker:

Which had closed the Grand Junction office and Andy was desperately trying to get people located, without their having to be fired.

Doel:

How many people were involved in the closure?

Shoemaker:

Well, as I say, a total of about 300 people were working on AEC sponsored work. That's just a guess. Two to three hundred, I would say. So it was a big wrench in the total effort of the Geological Survey, and a considerable effort was put into starting up a new program for the systematic study of the state of Kentucky, systematic geological mapping. Some of those people were transferred into water resources investigations in the water resources division. As it turned out, I think, few if any had to actually be fired because of the termination of the AEC work. But somehow in all this turmoil, the proposal which I had written up, which I was hoping would be taken to NASA, just sort of gathered dust on Anderson's desk. It didn't seem like a very promising thing to him, I guess.

Doel:

Did you know him well?

Shoemaker:

I didn't know him well at all, no. I knew him but that was about it. And so nothing much happened. The proposal just sat there. So at this point, I was starting to look around, because I didn't know whether the Geological Survey was going to go to the moon but I was determined that Gene SHOEMAKER was. So … So I had made a lot of contacts, particularly in Southern California with people at JPL and Rand. Nothing was happening on this proposal. I really didn't know how to energize it, how to get it going.

Doel:

Did you talk with Nolan about it?

Shoemaker:

I didn't go back and talk to Nolan about it. I was trying to work up through the chain of command, so my contacts were more or less with Klepper, and so nothing really seemed to be happening, but meantime through JPL, I learned — they were getting their effort cranked up to start to move at that time. They were getting the Ranger program under way. JPL had been transferred to the sponsorship of NASA from the Army at that stage. So they were just getting into gear to start a lunar and planetary exploration program, and they were looking to build up a scientific group themselves, and in fact they invited me to come join them, but meantime, the Aeronautical Chart and Information Center at St. Louis had gotten their hand in the game, and had begun developing a project to do the topographic, or more exactly, the cartography of the moon, and to produce maps, somewhat similar to aeronautical charts, of the lunar surface, and they had let a contract to Gerard Kuiper to personally produce a photographic atlas for the Air Force, ACIC was an arm of the Air Force, and so Kuiper was under way with this effort, and out of that the ACIC then began to develop experimentally a program to actually produce charts, maps of the lunar surface, shaded relief maps similar to the kinds of charts that are used in aviation. So they had sent a sample chart they had been experimenting with which included the region around Copernicus, and I saw this prototype chart in the office of Fred Eimar, who is one of the key people at JPL, who along with Elmer Hibbs was trying to start up a space science division at JPL. As a matter of fact, Eimar was a classmate of mine at Caltech. I'd known him for a number of years. JPL was in large part staffed by Caltech grads, so there was a kind of a natural association there.

Doel:

Who else did you know at JPL then?

Shoemaker:

The people who stick in my mind from that time are Eimer and Hibbs. Al Hibbs was a Caltech PhD in physics. So these were two that I knew, and I had gotten re-acquainted with them in connection with the Lunar and Planetary Exploration Colloquium. So Eimar showed me this map, and when I saw this topographic map, my eyes bugged out and I said, "Why don't you let me take this sheet back to Menlo Park and I'll get a copy made of it, and I will plot an experimental geological map on it?" Because I knew I had a very good photograph that covered the same area. And so Eimar gave me this sheet he'd just gotten from the ACIC and I went back up to Menlo Park and had it copied in the photographic labs of the topographic division, sent the original back to him, and I promptly sat down the next week and I generated the first prototype quadrangle map, geologic quadrangle map based essentially entirely on the details that could be analyzed in this superb Pease photograph from Mt. Wilson, and I said, "Now, this is the kind of thing I think we should push forward with, as a systematic program to map, to establish the stratigraphy, to unravel the stratigraphy and determine a geological time scale for the moon, " because after all what we're trying to do is understand lunar history. And so in fact, Eimar sent my manuscript map to the ACIC, and they printed it. They printed it in colors. Because this was just beautiful, it played into their long range plans.

I went back and got well acquainted with Bob Carter who was trying to get this program launched. So whether the Survey was going to go, whether or not, I was really going to get a lunar mapping program started. Well, it turned out by one of those curious flukes, I finally did succeed in getting the Geological Survey moving on the thing, but it came about in the following way. Charles Anderson was trying to figure out how to support all these people who had been supported by the AEC program, and among them were a group of chemists in a branch of the survey that essentially did a service work, chemical analysis for the other branches in the geologic division. These fellows were suddenly out of work. They had been working on analyzing rocks and ores for the AEC-supported program, and Anderson wondered whether there might be some support at NASA, and so he asked one of the men who had been doing mineralogical studies and isotope geochemistry on Colorado Plateau ore deposits to go over and make contact with NASA and see if there'd be any interest in possibly supporting some studies on say the geochemistry of meteorites at NASA. Well, it turned out this fellow was a very close friend of mine. His name was Loren R. Stieff. And Loren knew I was interested in the moon, and so he called me up and told me what was afoot, and I said, "Loren, we've got this other proposal on Andy's desk, for work that I had hoped would be taken over and presented to NASA, " and I sent him a copy of it. "Why don't you take that too while you go over there?" So it wasn't something that happened out of the formal administrative chain, but just purely by the coincidence of a friend of mine being asked to do this, I actually got the proposition before the house of the newly formed space sciences administrative — I've forgotten what it was called now — that was headed up by Homer Newell at NASA Headquarters. So Loren did this and basically we took over the proposal to do geochemistry and extraterrestrial materials plus studies of lunar mapping craters.

Meantime, John O'Keefe who had initiated the study with — that came out of the US Army Corps of Engineers — had now gone to NASA, and O'Keefe had a special interest in very peculiar glassy objects called tektites. O'Keafe thought that these might be pieces of the moon, and he was helping out at NASA Headquarters. He was the assistant chief of the newly founded theoretical division of Goddard Space Flight Center. But Headquarters was scratching for people to help organize and run the program, and so O'Keafe was spending some time downtown helping Newell's group get started, and so he fortunately learned about this proposal as well, and played a very key role in finally getting something going. A peculiar thing that happened was that the proposal landed on the desk of a woman astronomer by the name of Nancy Roman, and again, another one of these strange curious coincidences of history, Nancy knew a lot about the Geological Survey because her father had worked for the Survey. Her father was a mathematician and he had worked with a group in geophysics with the Bureau of Mines. That group at one point in time had been transferred from the Bureau of Mines to the Geological Survey. Well, old man Roman had done some rather innovative things on the analysis of magnetic anomalies in his younger days. By the time his group was transferred to the Geological Survey, he had essentially stalled out. He really didn't produce much professionally after that time. And as a consequence, he didn't get promoted and he felt like he hadn't been treated very well by the Geological Survey, and Nancy Roman had inherited some rather bitter prejudices about the Geological Survey as a consequence of this history. So our proposal landed on Nancy Roman's desk, and it wasn't going anywhere. Well, another curious thing happened, and that was, one of the fellows who had worked for me on the Distribution of Elements project earlier in the decade in Grand Junction, his name was Bill Newman, by that time was back in Washington, and Bill was the secretary of the Geological Society of Washington at that point in time, and by then I had really done some work on the moon and had some very specific ideas about Meteor Crater, and about crater mechanics and in particular how to apply it to the moon and to the Crater Copernicus, and so Bill invited me to come back and give a talk on the moon.

Doel:

Is this 1959?

Shoemaker:

This is in 1959, yes. And so I did that, and I went back, I was back in Washington. This coincided with a business trip, and I gave a talk at the John Wesley Powell Auditorium of the Cosmos Club, which is where the Geological Society of Washington had their meetings, and there were three talks on the bill that night. One of the talks was by Bob Jastrow, if I recall correctly. I've forgotten, maybe it was just Jastrow and myself. I'd have to go back and check. So we had dinner at the Cosmos Club, and I proceeded to get well waxed at dinner, and afterwards got up and gave one of the best talks, most important talks I ever gave in my life.

Doel:

That's wonderful.

Shoemaker:

I talked about the ballistics of the Copernicus ejecta deposits, and John O'Keafe was in the audience, and that's how I came to know O'Keafe. I'm trying to remember whether John, I think John was also at dinner with us. And so I established my relationship with O'Keafe at that point in time, so O'Keafe went to bat for us. He had originally stimulated, you see, this study with the military geology branch, and now he was trying to get NASA to do something with it, so he was backing it for us.

Doel:

He was influential?

Shoemaker:

Fortunately at that point he was very influential. In fact, he had done some very nice things, because he was the first person to sit down and analyze the tracking data on the earliest satellites, and discovered the pear-shaped earth, exactly, so O'Keefe's credentials were very good, and he had a lot of influence with NASA at this point in time. But we were bucking a pretty serious problem with Nancy Roman. Well, I was corresponding at this stage with O'Keafe and another very very curious thing happened. O'Keafe was of course pushing this whole idea of tektites, and he thought tektites were oblation droplets, droplets of melt that actually stripped off big things that had gone into nearly circular grazing orbits through the earth's atmosphere, and were melting off drops, and that's what they were.

Doel:

These were falling to —

Shoemaker:

— these were falling to earth. And I pretty soon was engaged in a very serious argument and discussion by mail with O'Keafe about all of this, and O'Keafe is one of these guys that, he gets deeply into these things by mail. He sent me some pieces actually of ballistic missile nose cones which I was going to take a look at.

Doel:

He sent you the physical nose cones?

Shoemaker:

Well, not the whole nose cone but a slice, a little slice for me to take a look at, and meantime, I was trying to convince O'Keefe of what shock material was like, shock melted material. I thought probably tektites were more likely to be shock melt rather than something formed by oblation, and so I sent him some little samples by return mail, just in a letter, of pieces of material from Meteor Crater, Arizona. This…so I had in this a little chip of very strongly shocked but not melted cornea sandstone from Meteor Crater, and then I had a little chip of the glass that I'd sent to O'Keefe. Well, of course, he was an astronomer, he didn't know what to do with these things, but he just hired a young geologist by the name of Paul Lowman at Goddard, so he showed these things to Lowman. Well, meantime, the Survey was trying to get this project going, and they had decided to ask Ed Chao, a mineralogist who Lawrence Stieff had located, to start to think about what could be done on a project for NASA, and Lowman and O'Keefe got in touch with Chao and stimulated his interest in this stuff from Meteor Crater.

Well, it was about this time that I had just been planning to unpack my stuff, which had remained packed up for about a year after moving to Menlo Park, and was in fact planning to get my Meteor Crater samples unpacked and have a look at them, and in fact at about this time, an article, very important article appeared in the JOURNAL OF GEOPHYSICAL RESEARCH by two men at the Geophysical Laboratory in Washington. One of them was Joe Boyd, who'd been a very prominent member of the Geophysical Lab, on the phase diagram for high pressure polymorph of silicon, and in this paper [R.R. Boyd and J.L. England, J.G.R. 65 (1960): 749], Boyd and England, the two authors had really determined the stability field for a high pressure phase that had been discovered by Loren Coes at the GE labs in Schenectady of SIO 2 which has sometimes been formerly referred to as co-site after Coes, who discovered all this, so it wasn't a proper name, really, it wasn't a mineral, it had never been found in nature. When I saw this paper by Boyd and England, this was in the spring of 1960 by now, our proposal was still languishing in NASA Headquarters, and in the early spring this paper appeared and I thought, well, I'd better get on the stick and see if I can discover — I thought, there's a good chance this high pressure phase might occur in these shock rocks at Meteor Crater. I had undoubtedly read and forgotten that R. Nininger had exactly the same idea, after coesite was discovered, after the high pressure formula was discovered. He had actually suggested in a book he'd written on Meteor Crater [Arizona’s Meteorite Crater: Past, Present, Future. Sedona, AZ: American Meteorite Museum, 1956.] that it might be looked for there.

Well, I had forgotten this. When I saw the paper by Boyd and England I thought, well, that's the thing to do. There's a young lady by the name of Beth Madson who worked on the same floor in the same wing of the building that I was in at Menlo Park who did a lot of work with X-ray diffraction, and I thought, well, I'll just get Beth to help me, and I was kind of waiting for Beth to return from leave, from vacation, and we would get to work on these samples. I hadn't proposed Beth yet but I was just at that stage. Well, it turns out Ed Chao was contacted by O'Keafe and Lowman, stimulated by these samples I sent in this letter. So just at the time I was going to look for coesite, I thought Ed actually looked at the little chips that I'd sent O'Keafe, but he told me later what he did is, he went over to the US National Museum and got some specimens and independently looked at it, and he beat me to the punch. The coesite was so abundant in certain stages of shock metamorphism that it was easy to pick out by X-ray diffraction. And the next thing I knew, I heard from Washington that Chao had found the coesite. This is a major discovery.

Doel:

That must have been a shock.

Shoemaker:

It was an incredible shock to me.

Doel:

Had you known Chao before?

Shoemaker:

I didn't know him from Adam. I'd never heard of him. All of a sudden, here's this guy who's beaten me to the punch on something I was poised to do. Well, at that point Beth had returned from her vacation, and we got all the samples out, and in a period of one day I'd defined the complete distribution of coesite at Meteor Crater. We published a joint paper, Chao and I and Beth Madson, in the SCIENCE REPORT [“First Natural Occurrence of Coesite (Arizona)” Science 132, 342, (July 22, 1960), 220-222]. But he must have been stimulated by my letter to O'Keafe.

Doel:

That's interesting.

Shoemaker:

Well, of course, O'Keafe saw this whole thing unfolding, and this was a pretty spectacular discovery, and it provided the ammunition that O'Keafe needed, and he rammed the proposal through over Roman's objections, and we got funded. But it was literally touch and go, for me. If it had simply stalled out at that point, I had standing offers to go to work, an offer from Will Kellogg at Rand and another one from Al Hibbs at JPL, and from Fred Eimar who was Hibbs' deputy. I would have left. I would have gone to work at JPL. That would have been the obvious thing to do. And Fred Eimar had been very helpful also, because he was pushing it from the other end, saying this is an important thing to do. So really it's thanks to John O'Keafe and Fred Eimar that there was enough push there to persuade NASA Headquarters to go ahead and fund what was really a rather modest effort, initially, to — but then the funds were transferred to the Geological Survey. And then at about that time when NASA decided that they would do it, Tom Nolan did get together with Homer Newell, and kind of established an agreement on the Survey commitment to follow through and carry out this thing.

Doel:

Do you recall discussions with Tom Nolan about that agreement, what the direction of that work was going to be?

Shoemaker:

Well, he had our proposal. I don't recall the time now. I don't recall whether I went back in to discuss it with Nolan or not. I do know that at least I have a vague recollection, I had dinner at one point with Nolan at the Cosmos Club or lunch some time in there. I think it was probably for lunch, and we just kind of talked about the long range program. It's terrible, my memory is really fading on a lot of these things.

Doel:

It's good to talk about them. Do you recall roughly what the budget involved when you began the program at USGS?

Shoemaker:

No, I don't have that fixed in my head. I think I've got that in some of the documents.

Doel:

It would be interesting to see.

Shoemaker:

We could look it up.

Doel:

There are a few other things I want to talk to you about that you've raised, before we go further forward chronologically. What were your impressions of NASA? Did you have any general impressions of the organization, what you saw as its strengths and weaknesses?

Shoemaker:

Well, after all, NASA was still getting itself organized at this stage. I guess, looking in from the outside and not really being in a position to see everything that was happening, it's not easy for me to make a very strong judgment about these things, but I was rather impressed that NASA was able to pull itself together and get organized as well as it did and as rapidly as it did. I thought that was really a very impressive show.

Doel:

Urey was also one of the early scientists involved with the project, the organization, from an early time. Did you have meetings with him, conversations, in the late 1950s?

Shoemaker:

No, I really didn't. Harold kind of circulated in a different orbit. But I was aware that he was on various committees of NASA, and he had a — he'd made some pretty strong contacts with people at the Goddard Space Flight Center, which was newly set up. The Goddard Space Flight Center was basically organized of people who were transferred from the Naval Research Laboratory. And this was the group that had really been involved in trying to establish an initial space program — that is, the satellite program. But they also brought on Bob Jastrow, and Jastrow was the one I think that really got Urey involved, and of course Urey had been thinking about planets and the moon for about a decade by then, so he had a lot of definite ideas and he was a very eloquent guy, very persuasive speaker, so he was very influential, and helped persuade, I think he really did help persuade NASA Headquarters that it was important to go to the moon, that is, to go to the moon with an unmanned exploration program, so Urey also was kind of a hero for the people at JPL who were also trying to get a flight program organized to go to the moon, and as between Urey and — and Jastrow was helping out at NASA Headquarters too.

A very small group of people really at NASA Headquarters that were exploring, pushing these ideas at the Washington end, and then a group of vigorous young guys, mostly aeronautical engineers, who were pushing to try to generate a flight program to go to the moon. JPL had been brought into the NASA family primarily with the charter that they would be the key arm of NASA involved with lunar and planetary explorations, so that was their baby, they asked for that and that's what they got. So there was an organizational group poised to go right forward, in Pasadena. But Urey was very influential, I think, in persuading NASA Headquarters to back this and to go forward with it, and of course he had a lot of contact then with the people at JPL. So he was after all one of the giants of American science at this time, so he carried a lot of weight, and he had a lot of ideas. He was just full of ideas. He's one of the most fertile and versatile scientists of his generation, and happily he had an interest in the moon. So it was a natural thing for Urey to be brought on board as a co-investigator on the first lunar project, Ranger, although Urey wasn't really that much enamored of taking television images of the moon, when he said, "What we want to learn about is the chemistry of the moon," and there was on the original Ranger a chemistry experiment. It was a gamma ray spectrometer, hung on a boom from that first primitive spacecraft, to measure the radioactive elements on the moon's crust. In fact, it was a very ambitious thing, and Urey and his colleagues at University of California San Diego were behind that and pushing it.

Doel:

Had they designed that instrument?

Shoemaker:

Yes. It was basically their proposal. So Urey was a co-investigator on the moon. Of course, what happened was that the block 2 Rangers didn't make it. There was also another very ambitious experiment which was the seismometer that Frank Press was Principal Investigator behind, so that this was going to be a balsa wood ball, so it had a rough landing on the moon and then a capability of righting itself and sending up a little antenna, and inside this instrument package was a seismometer very ruggedly built which would be un-caged, so you were going to measure the seismicity of the moon. You were going to measure some lunar chemistry. And the other thing would be to take pictures. Well, it turned out that block 3 Ranger, which ultimately did get to the moon, had only the television cameras. After the early failures, a decision was made to simplify the whole program, to try to do one thing, do it well, and so it just boiled down to taking TV images. But Urey nevertheless ended up a co-investigator on the final block 3 Ranger. Kuiper was designated PI (Principal Investigator) for that, and I had been invited at a very early stage by the people at JPL also to be a Co-I, so we were the original three investigators for this imaging experiment. Well, it was a very peculiar position for me, because here were two eminent scientists, Kuiper and Urey, who in the course of their time together at Chicago had a relationship that started out quite amicably, but then had gotten to be quite unfriendly, and I'd never really known the full details of where this enmity came from, but by the time I got involved in it as a co-investigator with this trio, Kuiper and Urey were scarcely on speaking terms, and we would have these interesting meetings at which all three of us were present, Kuiper on one side and Urey on the other and I'd sit in the middle, and I was speaking to both of these guys, but Kuiper and Urey wouldn't speak to each other. It was really rather funny.

Doel:

Remarkable.

Shoemaker:

Of course I thought they were both pretty good. And Gerard I'm sure wondered what in the world Harold Urey was doing on this experiment, because he really considered it was his experiment. But in any event —

Doel:

Did Kuiper talk to you about his troubles with Urey?

Shoemaker:

No, he never did. This is something that they pretty much kept to themselves, and I didn't try to pry into it, and I think at one time I probably had a better understanding of how this all started, but frankly I put it into the back recesses of my head and I don't really recall what it was that started all this off. It was probably some trivial thing that happened at Chicago, that got it all started. In any event, both of them had long since left Chicago. Kuiper had gone to the U of A and Urey to La Jolla. Later on, Whittaker, who was a protegee of Kuiper's, was added as a co-investigator to the team, after the initial successes of Ranger 7, and also Raymond Heacock who was the engineer who played a large role in the development of the television cameras and managing that effort at JPL was added to our TV team. It was really quite a surprise, actually, to the engineers, to everyone at JPL I think, what one could do with the television lenses. These people had worked awfully hard to try to make a spacecraft that would fly, and to actually try to get some data, and in fact the whole future of the lab had finally come down to writing or making an engineering success of Ranger, and there were six failures before one finally worked, and the lab was on the line, and finally a successful flight flew in 1964, and the television cameras turned on, and we got data back from the moon. But it was really fun to see what a revelation it was to all of these hard-working engineers when we actually had some data and could start to interpret it. They had no conception of what the science was that would come out of it. And it was really fun to see their eyes pop, when they had something to work with.

Doel:

How much time did the Ranger project take, proportionately say to other work you were doing?

Shoemaker:

Well, of course, it's a question of where to draw the line. Our first lunar geologic maps were done of the four seats, four quadrangles. In fact ACIC's program of mapping was scheduled around the unmanned lunar exploration program, where Ranger was going to go and where the Surveyor spacecraft were going to land, and so we were gearing our geological mapping to the same thing and we were trying to map the geology, again, of that portion of the moon that you could get to most readily with both Ranger and Surveyor, and so we were gearing our background geologic studies to this same end, whether you want to call that part of Ranger or not, I guess that's a matter of definition. In terms of work being done directly on Ranger, there were interminable meetings at JPL, and I spent quite a bit of time going to these, but until we actually had some data to work with, there wasn't a whole lot that I really contributed to the flight project. Once we had Ranger data, we were geared up to try to use it, and we were making some effort to be in a position to do that, so we did the first analysis, using a technique which we later called photoclinometry here, to actually reduce some of the data in the form of a reconstruction of topography of the surface, and I had started a lot of studies to try to understand the processes going on on the lunar surface. I had begun a program jointly with Ames Research Center at Moffatt Field to study small scale cratering experimentally, using light gas guns at Ames. I'd gotten involved and then they transferred Don Gault who's an aeronautical engineer at Ames into this to work on it, and so we had a joint project.

Doel:

You had initiated it.

Shoemaker:

I had initiated the effort to begin with, and assigned Henry Moore from our group to work with Don Gault at Ames on a joint program to study small scale cratering, high speed impact cratering. So with a specific goal of interpreting what I was sure would be a layer of fragmental debris produced by repeated meteoroid bombardment of the lunar surface, to try to understand the physics of that, how this layer evolved, and to be able to understand it. So all of that of course was part of the background scientific studies that I drew upon in analyzing the Ranger images. So I had work under way, research work, myself and people working with me, aimed very specifically at trying to understand what I called the fine structure of the lunar surface, before we actually ever saw it. Once we had the images at hand, we had a base on which to build and interpolate what was happening, and had a very different interpretation of that, by the way, than Kuiper did.

Doel:

I'm curious to hear that.

Shoemaker:

Well, it's all spelled out in the reports. Of course we saw, as I knew we would, this whole distribution of ever smaller craters, going right down to the smallest things that could be resolved, the last images taken before Ranger 7 crashed into the surface, and then we saw still smaller craters of course when we landed the Surveyor. But I was able to interpret the distribution, the form of the frequency distribution of craters as a function of size, on the basis of the continuing bombardment of the surface, and finally getting down to a scale at which there's not room enough left for all the craters that have been formed. You have craters upon craters and you have sort of a continual reprocessing of the surface. Harold Urey invented a nice word, he called it "gardening" of the lunar surface. We were in a position I think to explain both the size distribution of small craters, as you got to very small craters, and to explain the smoothing of the surface, the fact that when you got to small craters, besides the very sharp craters that you could see, bigger craters that you could see in your telescope, you finally got down to a range where clearly the craters were worn down. They were worn down by the prolonged and repetitive bombardment, and so we were in a position to re-interpret this process. I applied a standard geological name to the debris layer that we saw, inferred the debris layer and thickness from the data, and I called it the lunar regolith. This is a word now that’s become accepted.

Doel:

This was the first usage?

Shoemaker:

That's right — in general use. I don't think that one person out of a hundred could tell you where that word came from, but that's where it came from. It has passed into the general coin of the realm in scientific usage. You'd have to be a real lunar nut to know the history of it. So all of this was really part of Ranger studies, if you will, but it was background scientific research. Kuiper thought that these smooth craters were collapsed features on lava flows. And there might be some features of the sort, but they're predominantly craters that have just simply been worn down by the prolonged bombardment. So —

Doel:

Were you also in touch with Audouin Dollfus at that time about the nature of the lunar surface?

Shoemaker:

Oh yes. I was in contact with Audouin Dollfus. I knew him, had met him at many meetings. His approach to observing, planetary observing is quite different from mine. I come at things from an attempt to understand the three dimensional relationships of things on a planetary surface, in terms of the stratigraphy and structure and the history of what's there. This is a whole approach that's at the heart of geology but is very foreign actually to the way astronomers think about things, and Dollfus comes at a problem from trying to make a measurement of something, with the telescope, and the thing that he's been most widely identified with of course is his polarimetry. Making measurements of the polarization of reflected light. And so the kind of thing I did and the kind of thing that Dollfus does, they scarcely overlap, except to the extent that he was able to make certain definite interesting statements about the particle size and the state of the material that was beyond the limit of resolution even of the television cameras. One could infer from his polarimetric measurements that indeed the vast bulk of material on the lunar surface was very finely pulverized, for example, which I could also demonstrate theoretically from our experimental work jointly with Ames. We could predict the size distributions of fine particles and one would expect in fact that the lunar regolith was made up of this very fine particulate material. So there was a point at which the kinds of things that we did did meet and overlap. And we did consider at one time, as I mentioned, to use Dollfus's technique to try to characterize geological units on the lunar surface. But as it turns out, there's a direct and very strong correlation between the polarization of light reflected from the lunar surface and the albedo of the surface, and you can really get that information by a simpler and more direct method. So beyond the fact of demonstrating that the surface is pulverized, it turned out not to be a very useful technique for us in geologic mapping. We could get the albedo by very direct observations. We ultimately did produce a map of the albedo at telescopic resolution from a sub-earth side of the moon, which we employed. Albedo was in fact one of the important properties which we used in discriminating geologic units of the lunar surface.

Doel:

Before we get into the origins of the astro-geology here at the USGS, let me just go back to one or two points that you raised and also to the PhD work that you were doing in 1960. You mentioned a moment ago about the Lunar and Planetary Colloquia in California. Do you recall in particular any of the colloquia that you attended that made a strong impression on you? Was there a particular —?

Shoemaker:

— they were all published, by the way. I should say North American undertook to publish the colloquia.

Doel:

Does anything stand out in your mind? In particular?

Shoemaker:

Oh, we had a large range of things. One of the fellows who was at North American at that time, a geologist that I had known, he had actually been at Columbia and had worked in one of the uranium areas in the volcanic rocks in the very western side of the Colorado Plateau was Jack Green, and meantimes Green had found a job with North American. North American was hoping to be involved in the lunar exploration program. That's why they hired him. And Green was a fellow who was pushing the volcanic origin of the lunar craters, and so there was a fair amount of volcanic versus impact debate, thanks to Jack. We had a very friendly relationship but disagreed completely about the science. And Jack went around the country giving lots of talks, trying to uphold the volcanic origin of the lunar craters for a long time, but he's now disappeared from the lunar scene essentially entirely. He's out of that business. The last I heard, he's teaching at Long Beach State College, in Long Beach. He hasn't been involved in lunar work for a long time.

Doel:

How many people attended the colloquia?

Shoemaker:

Oh, I guess a couple of hundred. It varied from time to time. It was really pretty much of an informal thing. Anyone could come who wanted to. It was a good way to get together and seeing who was doing what, at the various stages.

Doel:

Do you recall meeting with any particular individuals?

Shoemaker:

One of the fellows that came, I got acquainted with first at the colloquia, was Carl Sagan. I've forgotten —

Doel:

He had just gotten his dissertation.

Shoemaker:

He had just finished up at the University of Chicago, and Carl of course was promoting his ideas about where life might be elsewhere in the solar system at that time.

Doel:

Was he also talking about the Venus atmosphere? Did you have any conversations with him about that?

Shoemaker:

Yes, he was talking about Venus, among other places, at that time. I did have conversations, but I can't bring up their substance at this point. But Carl and I did get acquainted at that time.

Doel:

In 1960 you were awarded the degree, PhD from Princeton for impact mechanics of Meteor Crater. How did that come about?

Shoemaker:

That's just because it was a long delayed thing. Actually I turned in — my deadline had run out in 1959, and I turned the thesis in to Princeton in the late summer in 1959. And then I went back, shortly after the semester began in the fall, and gave the oral defense of the thesis, but my degree was awarded the following spring, so that's just what the timing was there. And I think we've talked about that, I'm not sure, on the tape. We haven't? So. My original thesis topic had never really surfaced on the top of my pile. I had gone back to Princeton in the fall of 1953, having stayed out two years to start the Distribution of Elements Project, and went back, and spent another academic year at Princeton. Actually it was only about seven and a half months or so, when Carolyn and I were there. By that time I was married and had a small daughter, and once again, I ended up not having a place to stay with the arrangements at Princeton. There was some graduate student housing for veterans at the time but I wasn't a veteran, and we ended up living in a little chicken form just on the outskirts of Heightstown. It wasn't very satisfactory. I had this old '46 Ford which was on its last legs, which I drove into Princeton every day, leaving Carolyn on the chicken farm.

Doel:

It's a good ten miles away.

Shoemaker:

Yes. It wasn't a very good year for her. We were glad to pick up sticks and head back. We were so damned glad to get back to Colorado it hurt. But anyway I did finish up the course work and took my orals, and left Princeton, not having finished writing the thesis as I had intended. And time dragged on, and so many other irons in the fire that I was just having a very hard time getting back to finishing writing it up. Meantimes the quadrangle maps, some of them that I had prepared, had been published, and I was writing papers on the salt structures of the Paradox Basin, straddling the Colorado-Utah border. So I was writing about it, but I wasn't writing my thesis, and after some hints had been dropped by various members of the faculty, I realized the thing to do was simply to take a paper that was going to be written, something off the top of my file rather than the bottom, and send it in, and that's how the work at Meteor Crater then became my thesis, really as a convenience, if you will, to satisfy the degree. It was not something that was really supervised by Princeton, but I did use the materials. Some of the materials had been deposited at Princeton University by Daniel Maroe Barrier, in my study of Meteor Crater. And Princeton was quite happy to accept that thesis, and so that was — I got it in, just in the nick of time to meet my five year deadline.

Doel:

Do you recall in particular any conversations you had with Harry Hess?

Shoemaker:

Well, I had lots of conversations with Harry Hess. Harry by that time was chairman of the department at Princeton, and he was the one I went to see, when I realized that as the deadline was getting nearer, that it would be a good idea to change my thesis topic. So on a trip back to Washington, I made a side trip up to Princeton to see him, and I proposed the idea of switching my thesis from the salt structure I'd been working on to take this other work which was a bird in hand, and simply write it up for a thesis, which he accepted with alacrity.

Doel:

Did you talk to him at all about continental drift and plate tectonics in the late fifties?

Shoemaker:

Oh yes. I had ideas. I was trying to understand what made the uplift of the Colorado Plateau, and in fact, I was playing with the idea that there had been lateral transfer of material by convection beneath the Plateau. Harry at that time had just come up with a different idea, and he thought that what produced uplift and subsidence in the crust of the earth might be the hydration and dehydration of the upper mantle. In fact, Harry was an expert on the mineralogy of these rocks, and he said, "Well, uplift might be produced by the formation of serpentine, out of the olivene rich upper mantle," which is a reaction that proceeds if water is available at the right temperature. Actually the temperature has to be low enough. If you increase the temperature, the water is driven off, and you convert the minerals back to Olivene. So Harry imagined that if water was generally percolating up through the mantle, if the temperature went down, you would hydrate the mantle, and the phase change from olivene to serpentine was a very large change in specific volume. Actually a change going from about 2.7 — going from olivene at about 3.3 grams per cubic centimeter, to serpentine at about 2.7 grams per cubic centimeter, which is a change of about 20 percent. So that could give you large volume differences, and as temperature goes down you get expansion and serpentization proceeds, and then as the temperature went up again, you reconvert this material back to olivene, drives the water out, and it subsides. So that was his explanation actually for midoceanic ridges at that stage, and he suggested this was what was happening that accounted for the uplift of the Colorado Plateau. And I toyed with that idea too for quite some time after he suggested it, and wondered whether there were ways of testing that from the thermal history of the Colorado Plateau. As we know now, it wasn't the right idea. But he was a very fertile fellow. It was only somewhat later that he put forward his idea of spreading at the midocean ridges. He hadn't evolved that idea at that time. So we had a lot of arguments, because I was interested in uplift of the Plateau in particular. I was much captivated by the notion that he put forward.

Doel:

Did you also talk with him about the nature of research programs that you hoped to see done with planetary objects?

Shoemaker:

Well, Harry was interested. He had done some work on meteorites, so he had an interest in the whole area of the space program. I had of course confided in Harry my interest in the moon. He knew about this. At the time that I talked to him about submitting a thesis on Meteor Crater, I told him I was hoping to be Johnny-at-the-rat-hole ready to be there to be one of the first people to look at lunar photographs, and he figured I probably would, having thought about it long ahead of time, probably would be in a very good position to do just exactly that. It was — as a matter of fact, it was due to Harry that I got involved in the first effort to select astronauts, scientist candidates for astronauts, because Harry inherited the chairmanship of the Space Science Board at NASA from Harold Urey when Harold relinquished that job. He passed the baton to Harry Hess. And this is about the time that NASA was, among other things, started to consider the recruitment of scientists to the astronaut corps. This was something I'd gone back to Washington and spent the better part of a year working directly at NASA Headquarters in hopes of helping, partly in hopes of helping stimulate NASA to do this.

Doel:

That was in 1962?

Shoemaker:

I went back in 1962. Right. To do that. And it didn't happen while I was there, I regret to say, but it did happen shortly after I left. And so Harry knew of my interest in the whole area, and asked me to be on a committee that would undertake to try to plan how to review the — how to advertise the thing in the first place, and then to review the applications, which NASA did ask the National Academy to do, when the time came. So I was on the committee, at the invitation of Hess, to do that, and then, it turned out when the time finally came to review the applications, Hess was on a sabbatical in England at the time, so he asked me to take over with the chairmanship of that committee. It's kind of an ironic turn of events, because way back in 1948 I had imagined that there would be some point in time in which the National Academy of Sciences would be asked to review the qualifications of scientists who wanted to go to the moon, and my goal then had been to be standing at the head of the line as an applicant. I never pictured that I would end up chairing the committee to review the applicants.

Doel:

We're talking about the work that you were doing when you were in Washington for the year.

Shoemaker:

Well, perhaps it's best to ratchet back a little bit. We did get the astro-geology program. Funds were transferred to the Geological Survey in the summer, in August of 1960, and we did formally start the Survey program at that time, and it grew slowly at first. Two of the people that I had met in Washington earlier, in trying to see who would be interested in coming into such a program, did get transferred to our effort. One was Dick Eggleton, and he had been in Washington. Another was Charles Marshall. They'd both been transferred out to Menlo Park to work with me. And I hired on some other people at an early stage. One was a fellow by the name of Henry Moore whom I'd known in Grand Junction. In fact, Henry had worked with me in the field on some of the diatremes in the Navajo country, and he was just about that time finishing up his PhD at Stanford, and so I asked him to come and join us, and in particular to work on the impact cratering work, the experimental work with Don Gault, and that turned out to be an excellent choice, and he also participated in some of the early lunar mapping. So there were — we initially then got started with two people that shifted to Menlo Park, and a fourth person in lunar mapping who started out initially with us was Bob Hackman who had gotten involved as a photogeologist that was asked to come in with the military geology branch study, and worked on that first attempt to do a map, geological map of the moon. And then I invited Bob to work with me to kind of bring our first prototype map of the Copernicus quadrangle into shape, and so he added some of his own ideas to that map, and we put that thing together jointly, so Hackman however really had his base in Washington and stayed there. Unfortunately he was kind of alone at that stage. He didn't have close colleagues to work with. I tried my best to get Bob to come to Menlo Park so he could join in with the rest of our group, but he adamantly refused to move, which I think in the end was kind of unfortunate, because it would have been a much more fruitful effort if he had been willing to join us. So we had a small group then working on lunar mapping.

Doel:

Did you have special qualifications in mind for these people when you made the invitations?

Shoemaker:

The qualification was, they needed to be interested. That makes a difference. Actually, it turns out that none of the people who originally joined me in this effort were particularly strong scientifically. But they were people who were at least willing to get involved. I have to say that most of my colleagues on the Geological Survey thought the whole thing was a joke.

Doel:

Even then?

Shoemaker:

Oh yes. Geologists at Menlo Park really took huge amusement at the whole business. They really had no faith at all that NASA was going to send a spacecraft to the moon or any place else. They were really pretty remote from it. It's amazing how parochial different scientific disciplines can be. And this was so foreign to them that it was just beyond their ken, that's all there is to it. So, somewhat to my disappointment, there weren't really very many people who had much interest. And fundamentally I had to go out and recruit and build from scratch to get people into it. I did meet a young fellow who had just finished up his PhD at UCLA by the name of Don Wilhelms, on one of my trips down to the Los Angeles area. He came to see me and I ultimately hired Don Wilhelms, and he came and was one of the mainstays of our lunar mapping. Don was the one who in later years then really carried it forward. Then I had met another fellow. He wrote to me and I went and talked to him on one of my trips back East. It was Jack McCauley. And so basically I recruited the key people who really carried on lunar and later planetary geological mapping forward, they're people that I went out and recruited outside of the Survey.

There was another young guy on one of my trips that I learned about who was just finishing up a PhD at Yale, and because he was a Brit and didn't have citizenship, he had to go back out — in fact, he came in on a student visa, and he had to go back out of the country in order to be able to come back in, so he had gone to Canada, to meet these requirements, but I hired him when he was getting to a point where he could come back into the United States. His name was Michael Carr. And I got him to join us in Menlo Park. I hired Michael originally to try to work on — we were hoping to develop some techniques to better understand the equation state of rocks. I didn't hire Mike to work on lunar mapping. But every geologist who came into the branch at Menlo Park was pressed into service, because we were trying to expand and carry out this program, so everyone got assigned to map a lunar quadrangle and that was part of their job, and so that's how people like Moore and Carr got into lunar mapping to start with. And of course Mike in later years became one of the real mainstays in the planetary geology effort. But some of the key people early on were Wilhelms and McCauley, Carr, and I did persuade one of my long time acquaintances who'd been in the uranium program in the earlier days, a contemporary of mine who'd actually worked up in Wyoming, by the name of Harold Masursky, and Harold and I had somewhat parallel careers. We knew each other. I thought Harold was a very facile person verbally, and I knew he was very imaginative scientifically, very bright, and I invited him to join us. That seemed like a good opportunity to Hal, and he did, and so he became involved then also early on in the mapping effort. So it was a matter of going around and deliberately seeking people out and recruiting them.

Doel:

Was that in the early sixties that you moved the branch down to Flagstaff?

Shoemaker:

Well, at the early stages of the effort, we knew, I knew right from the beginning that we would need to go to the telescope to do direct visual observations, to get the high resolution details. Mind you, this was before we had any spacecraft data on the moon. So that in addition to using the available good telescopic photographs, a key part of the effort was training all of these men to observe the moon at the telescope. We needed to get time on telescopes that had sufficient aperture suitable for the purpose, and we made arrangements to work with the 36 inch refractor at Lick Observatory.

Doel:

This is while you were still at Menlo Park.

Shoemaker:

Still at Menlo Park, and so that was near at hand, and we were going to get some time at Lick. We made arrangements with Lowell Observatory to come to Flagstaff and spend some time on the Clark refractor here at Lowell. But as we expanded the effort, it soon became apparent that we were simply not going to get enough time as guest observers on these existing telescopes to do the job. If we were really going to carry the work forward at an adequate rate, we needed to have a telescope dedicated to the work, one with adequate optics and established at a site where the astronomical seeing was adequate to do the work. And so at a very early stage, we started deliberately thinking about building our own telescope. Well, at about this time, I was on a field trip. We were here in Flagstaff on a trip, observing the moon at night at Lowell Observatory. Another person I'd hired on was a young fellow named Danny Milton who joined us very early, and Danny worked on lunar mapping and also on field studies, on impact craters, and we were spending time during the day out at Meteor Crater, Arizona, 40 miles out of town, and at night we were on the telescope. Danny and I were sharing a motel room, and as we were getting dressed one morning he said, "Why don't you move the branch to Flagstaff? Here we are, we're doing these two kinds of things, here's the place. "And the more I thought about it, it seemed like a very very potent suggestion. We knew Flagstaff was a good site. But we actually did go through the procedure of considering various sites. Kuiper urged us to come down to Tucson and set up shop beside his enterprise. We also thought seriously about Hawaii, and Gerard at that time was exploring, pushing very vigorously the idea of developing observatory sites on Mauna Kea.

Doel:

And infra-red telescopes.

Shoemaker:

Well, he was thinking of a whole wide range of things, and the infra-red advantages at Mauna Kea were one of the things uppermost in his mind. That was one of the things he was especially interested in. But he also knew that Mauna Kea would probably be a superior site for astronomical seeing as well. So we seriously thought about Hawaii as an alternate site and also the Tucson area, maybe setting up on the Catalina Mountains, but in the end, Flagstaff was a place I'd always kind of had my eye on, and it was just a superior place to live, and this looked like a golden opportunity to make that come to pass. So when we finally did make the decision, it really wasn't a contest. Flagstaff was the place. I had in mind that this would be an excellent site because of the diversity of geology, to train astronauts, to test our ideas about geological exploration of the moon, both the unmanned parts, what we might do with Surveyor. I was at that time a designated Principal Investigator for the television camera on Surveyor, and I thought we'd develop our ideas about how one might systematically go about exploring the moon with both Apollo, but looking beyond Apollo, much more advanced techniques of carrying out a thorough manned exploration of the moon, and it seemed to me that northern Arizona would be a perfect base to utilize the surrounding topography and geology as a test bed for those ideas. But of course, not least among these things is, it's a nice place, and that's very important in building a program, to have a places that not everyone necessarily wants to come and live, but a lot of people are strongly attracted, and it proved out. I think probably that was the single most important reason for having come to Flagstaff. It enabled us to attract and hold some very talented people like Larry Soderblom for example, and the Kiefers, who came in later years. So that was very much on my mind as well, besides this being the place where personally Carolyn and I wanted to live.

Doel:

It's a beautiful view out the window now as we're talking.

Shoemaker:

So all of those were factors, but the key point that really brought about that decision to come was building the telescope. So when I went back, I was invited to go back to NASA Headquarters in 1962 to help them develop the management basically for the scientific program for Apollo, and I accepted that offer, first because I was really interested in trying to help science planning for Apollo get off the ground, but I also saw that it would help in getting all of these things going. I thought it would help in getting the telescope built, which it did. It consolidated our plans for doing that, and to provide some long range support for the effort here.

Doel:

What were your initial plans for the telescope?

Shoemaker:

Well, we anticipated that we would use this in completing the mapping of about 45 or 50 quadrangles on the sub-earth side of the moon, the side we could study from a telescopic base. And so we anticipated that this would be completed in a time period of four or five years. And so we deliberately set out to design the building that we're in right here, that would house this effort. It was scaled for the level of manpower that I thought we would have available, and would be a project that would be completed over the time period leading up to the first manned landing. So those were our goals. I was co-investigator on Ranger at the time we came out, and I was Principal Investigator for Surveyor. I'd been designated that before going back to NASA Headquarters, and I had recruited some people to come to work specifically on the Surveyor project. The original spacecraft had two television cameras on it, and we were planning to study the lunar surface stereoscopically, and we were working on developing techniques, photometric techniques to do that.

Doel:

This was all work that you were doing while at NASA Headquarters?

Shoemaker:

Well, we weren't prosecuting it very vigorously then, but as soon as I got back in the summer of 1963, that's when we essentially moved the branch headquarters from Menlo Park to Flagstaff. We were getting the telescope nearing completion and ready to use, and so we were trying to get set up here. Our building wasn't built yet, but plans had been made for it, and it was in process. So it was under construction certainly after we got here. We occupied a wing of the Museum of Northern Arizona, which was built to house us for the interim time period, and we leased it from the museum until our new building could be built here. So we had an expanding program on the Surveyor television experiment, ongoing work in anticipation of the images we were going to get back from Ranger, as well as the systematic lunar geologic mapping, and we were continuing of course field studies of Meteor Crater. Not everyone came from Menlo Park. There were some people who were dyed in the wool Californians, people who preferred the urban environment of the San Francisco Peninsula, and elected to stay in Menlo Park, and so we didn't try to move everyone here. We left a contingent there to continue part of the work in Menlo Park, and part here.

Doel:

Let me go back just a moment to touch on a few other important things that you were involved in in the very early 1960s. Just prior to the Kennedy Administration, there had been discussion of plans to detonate an atomic device on the surface of the moon. This was approximately 1959 [actually April 1958]. Were you aware of any of those discussions? Were you asked to make comments on them?

Shoemaker:

No. I'm not really sure what you're referring to.

Doel:

It was a plan that had been put forth within the Presidential Science Advisors [Gerard Kuiper and Thorton Page includes a discussion of this proposal in their draft “A Survey of Fruitful Rocket Experiments on the Moon,” dated 8 April 1958], where a device might be exploded on the surface of the moon to create an artificial crater. It was discussed in '59.

Shoemaker:

Oh my goodness. Well, if I knew about it, I've forgotten about it. I think Nininger had actually suggested this in a publication, as a way to sample the moon.

Doel:

To send a piece back.

Shoemaker:

To capture a piece without landing. It wasn't something that was thought through in any detail. It was a wild idea of Nininger's. But I didn't know that there had been a serious scientific discussion of it, or if I did I've forgotten it. It's kind of a harebrained idea.

Doel:

Did you have much contact with the staff astronomers at Lick and Lowell during the time that you were making observations?

Shoemaker:

Well, we certainly had a lot of contact here at Lowell, and of course the ACIC had a team of people by this time, established at Lowell. They'd made a contract with Lowell Observatory to have a group of observers. These were the people who were basically airbrush artists who were then filling in details on the lunar maps that they were producing, basically for exactly the same reason that we went to the telescope, to get the details you couldn't gather out of the photographs. They did a fine job. They had an excellent group here, under Bill Canel who was in charge of this group, and two of the people that had quite a bit of experience in observing … later joined our group that are here now. They are two of our old hands who have really been responsible for many of the best maps of not just the moon but of the planetary surfaces of other satellites. This is Pat Bridges and Jay Lynch, who came from that originally ACIC group. So we had close contacts with the ACIC people that were housed at Lowell Observatory. A building was actually built for them there, for their office and for their cartographic work. And of course, I knew the director at Lowell, John Hall, and I knew other people who were working at Lowell at that time. E.C. Slipher was still alive at Lowell Observatory in those days. Bill Sinton had been a prominent member of the staff here and had done some interesting observations. He was a pioneer in infra-red observations as applied to planets. In fact, h e had stirred up a considerable storm of interest in erroneously reporting an absorption band of chlorophyl from Mars.

Doel:

His vegetation studies.

Shoemaker:

But Bill then went on, he left Lowell Observatory and went to Hawaii, and has continued his work there. So we were, yes, in a broad way, we were in contact with people at Lowell and also at the Naval Observatory. I knew most of the people at the Naval Observatory as well.

Doel:

Which had also set up a telescope here in Flagstaff.

Shoemaker:

Well, the Naval Observatory established the Flagstaff station, and this is the observing facility for the Naval Observatory. Hardly any observing work is done at the old observatory.

Doel:

Right. I know that our time is getting a little short. Let me turn to one other development that you were involved in in 1960. You were going to present a paper in Copenhagen at the International Geologic Conference concerning Meteor Crater, and you had also intended to study the Reese Formation in Bavaria in Germany.

Shoemaker:

Well, I had been thinking about going to see the Reese Crater for several years, at that time. During the period that I was working on Meteor Crater in connection with the MICE Project, I took the opportunity when I was traveling back East to actually go and visit all the sites of the so-called crypto-volcanic structures. In fact, I'd begun this work in connection with things I was doing at Hopi Buttes. Originally, I had been somewhat persuaded of the arguments of Walter Bucker, who was the first person to systematically describe these structures, that they might be of volcanic origin. But after I really sat down and worked hard on the mechanism of violently eruptive volcanoes in connection with the MICE Project, I finally realized that volcanism will not produce structures like the so-called crypto-volcanic structures, and I really soon became convinced that these really were impact structures. And in connection with this, of course the Reese was a prominent feature that had been a subject of vigorous debate in the geological literature.

It had been intensely studied by the Germans for a period of about a century, and the more I read about the Reese, and I got translations of some of the German papers, some of the summary papers, and I plowed into it as best I could with my fragmentary German, the more I became convinced that the Reese must be a large impact crater. So in the spring of 1960, I already had planned in fact to present a paper on Meteor Crater at the International Geological Congress at Copenhagen, and in fact, the way my thesis came about is, I wrote the — you had to submit the paper about a year ahead of time, and that manuscript for the Congress, and so I sat down and wrote up Meteor Crater for the Congress. Well, it turned out that it came out too long a paper, the first time, so I took the long version and turned that in for my thesis, and then I proceeded to shorten it down to get within the page limit for the Congress. But all of this had been done in 1959, a year ahead. So I had already made plans to go to the Congress, and had gotten permission to go and present the paper, and I figured, when I got to Europe I was going to go look at the classical original Mars type volcanoes, the Mars of the Eiffel region of Germany.

I was going to look at the diatremes in Schwabian Alb and I was going to go and look at the Ries, which was also on the Alb, and the Steinheim basin which is a smaller crater, which is the type of the crypto-volcanic structure. So all of these were features I had been reading about and trying to build up some background knowledge, and were on my planned itinerary, to go and spend not just a week or two at the Congress, but to spend something on the order of a month and do some geological sight-seeing in Germany. That was part of the plan. Well, it was after all these plans had been laid that we discovered coesite at Meteor Crater, and the timing couldn't have been better. When we found the coesite at Meteor Crater, I knew immediately that I was going to go to the Reese, I knew exactly where I was going to go, and I was going to find it there. It was just sort of a set up thing. Because I had read the descriptions of the material that the Germans called suevit I anglicized it and called it suevit. And that looked to me like it was a shock melt. I was just sure of it in my bones. This is a very specific target. The one thing that I didn't anticipate was that during that spring, my father was in the terminal stages of cancer, and died actually before we left, so at a very late stage, we made plans to take my mother with us. It was only about a month after his death that we departed for Copenhagen. I had arranged through an American distributor to purchase a Volkswagen camper, which we received on arriving at Hamburg, Germany, and we were going to tour around. We went early, ahead of the Congress, to do this field trip. Sort of the main change was the decision at the last minute to take Mother with us.

So the three of us then proceeded. We left Hamburg and we headed for the Eifel region and first visited the Mars there and the lockers and then we drove on further south, and proceeded on through the Stuttgart and then headed east to the Ries, which is a giant crater in the Schwabian Alb about nearly 30 kilometers in diameter. We drove across. It was a rainy day when we left Stuttgart, drove across, got to which is an ancient world town out in the middle of the Reese. It was getting fairly late by the time we got there, so I drove across the Ries to Nordlingen on the far side where I had one of the German geological maps, with the location of some quarries, and we went to — just as the sun was going down, we got to one of these quarries, which turns out to have been one of the major quarries. This suevite was being quarried in it for the manufacture of concrete, and it turned out, it was an excellent mix that goes into concrete manufacture. It was being actively quarried at the time, and I got to the quarry, and got down and had my first close-up look at the suevite. I looked at some of the pieces of shocked granite, partially shocked melted in the suevite, and as soon as I saw it in the hand lens, I knew I had it. I took two specimens that night, and then we just drove off in the woods and camped, which is what we had been doing. If we could find a patch of woods somewhere, we just pulled off and camped with our camper. Next morning, I drove back to Nordlingen and mailed these two specimens direct to Ed Chao in Washington, sure in my bones that I had sent him samples of coesite. Within a few days, Ed had received these by air mail. He looked at it, picked out the most promising grains, put it under the X-ray and there was the coesite.

There was never any doubt in my mind it would be there, and it was. So we had this wonderful fingerprint for identifying shock processes. And then I spent, oh, about two weeks, and I went to lots of the major exposures, which were mostly quarries, to look, to examine the suevite. I went back and marvelled at this Cathedral or church in the center of Nordlingen which is built of suevite, and looked at all the beautiful very peculiarly formed bonds of melted material that were a part of the suevite, and admired this church. It was a church built out of material that I knew, just knew, had coesite in it. I took pictures of the church as well. But I went to lots of key locales. The German geologists interpreted the suevite as volcanic, and I went to the places where they thought the volcanic events were, and became convinced that these were simply sites where either the suevite had filled a fracture in the underlying brecchia, or had been faulted against brecchia. They were not volcanic events.

Doel:

Were you meeting with the German geologists?

Shoemaker:

Not a bit, no. I didn't know a single German geologist there. I was just a young American geologist on a vacation. It was a postman's holiday. So I didn't know a single soul, academic or otherwise, in Germany. We were just American tourists doing something very un-American. Very few people guessed we were Americans. Americans didn't go traveling around like we did in a VW camper, camping out. They thought we were Swedes or Englishmen or something. So there was — I had no contact with any German scientists while I was there. I was just rubbernecking, looking around, but rubbernecking with a purpose, and of course by the time then we arrived at Copenhagen, we already had a very important discovery. Well, Bill Pecora, who was later the director of the Geological Survey, was there at the meeting, and he perceived that we had a diplomatic problem. I hadn't talked to any Germans. Here I was poaching on their turf scientifically, so to speak. But I was scheduled to give my talk anyway and we did announce that it was coesite, at the Copenhagen meeting.

Doel:

You did announce that?

Shoemaker:

Yes. Of course that wasn't part of the original paper. Well, this discovery stirred up a storm of activity among the German geologists, and poor old Wagner who had spent the best part of his career studying the geology of the Reese and propounding the volcanic origin of the structure was never reconciled to the idea, but there were others who immediately perceived the significance of this and proceeded to study the Reese from the standpoint of an impact crater. That was a big breakthrough, because this was the first demonstration that indeed there are very large structures on the earth produced by impact, structures very much larger than Meteor Crater, and of course this provided a very important link in identifying craters on the moon as of impact origin. Kuiper had a rather different idea. He thought that almost all of the craters — he was convinced of the impact origin of the lunar craters too, but he did not appreciate the rate of impact that's gone on over later geologic time. He thought that probably almost all of these craters dated back to a very early point in lunar history, and therefore he considered that the mares were formed very close to the time of the accretion of the moon, and that the craters that were formed post-maria were also very early, and so I differed from Kuiper right from the outset on this. I was convinced that the crypto-volcanic structures of the central United States were impact structures, that the Reese was an impact structure.

I could make a rough estimate of the cratering rate in late geologic time, and was convinced that the record of craters on the moon or maria were actually representing a cumulative record distributed over geologic time, and were produced by bombardment, chiefly by earth-crossing asteroids, of which about nine had been discovered up to that time. So I was convinced that we were only seeing the tip of the iceberg, as far as earth-crossing asteroids were concerned, and that asteroids that were crossing the earth's orbit and colliding at about the present rate were probably responsible for the craters, the post-maria crater record. It was this kind of theme that I developed then for my first major paper on the moon, because I was attempting to estimate the history, establish the time scale for the geologic units [Geological Interpretation of Lunar Craters in the Moon: Its Astronomy and Physics (NY, Academic Press, 1961)]. The Reese figured very prominently in trying to set the stage for the time scale.

Doel:

Do you recall others who were involved in that debate, besides Kuiper?

Shoemaker:

Well, there weren't very many of us, you know. Up until we started getting spacecraft data back from the moon, there were some people in the Soviet Union. There was a geologist who had attempted to do a geologic map of the moon in the Soviet Union which was published, which just was nonsense. It wasn't — it was pseudo science.

Doel:

Do you remember his name?

Shoemaker:

I don't know. I don't remember it now, no. He didn't have any grasp of the stratigraphy. For that matter, the stratigraphy really was my invention, and I developed a whole program to try to pursue that. We were trying to really map the moon by time units, by stratigraphic units, which then could be sorted out by time of formation. So that outside of our group in the Geological Survey, and a smaller group that Kuiper had with him, a young man by the name of Bob Strom had joined in, a geologist, a young lady by the name of Ann Palm also worked for him for a while, and Whittaker and Di Arthur who are not geologists but were working on the moon with Kuiper in Tucson, outside of our two groups, there really weren't very many. There were some people in Germany who were interested. There was one, I can't think of his name now, one older German geologist who had paid some close attention to the moon. But there were very few people. In 1960 of course I was just getting things organized in the Survey, so I knew everybody who was working, who was really doing anything active.

Doel:

There are a number of things that I'd like to talk to you about in our next interview, including some scientific details of the stratigraphic program and your later work with the Survey and NASA, but we're just about out of time now. Let me ask you one last question concerning Princeton. During the two years that you were in residence there, did you have any contact with the astronomy department, with say Lyman Spitzer?

Shoemaker:

None at all. As a matter of fact, when I was a graduate student at Princeton, I had not yet really gotten into the business of impact craters. I hadn't thought about Meteor Crater at all. I had thought about the crypto-volcanic structures, and I thought that they were volcanic. It wasn't until later, when I really braced the problem of the mechanics of diatreme eruptions seriously, that I concluded they were of impact origin, and after I had started working on Meteor Crater, that I really realized the difference and was very sure that they were of impact origin. So at the time I was a graduate student at Princeton, I really had not gotten into these things, and I hadn't gotten to the point of thinking seriously about astronomical observations. It was too early.

Doel:

Well, we've covered an awful lot of ground today, and I want to thank you very much.

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