Scientist Profile:  Paul D. Spudis

Previously posted at “Earth and Sky” web site


Interview conducted by David S. F. Portree, January 17, 2003


Paul D. Spudis is a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Baltimore MD.  Though he specializes in lunar geology, he has also studied the geology of Mars, Mercury and many other worlds.  He was deputy leader of the Science Team for the Clementine lunar mission in 1994 and has participated in NASA and National Academy of Sciences committees that helped shape future space exploration.  Dr. Spudis received his B.S. (1976) and Ph.D. (1982) degrees from Arizona State University in Tempe and his Sc.M. (1977) from Brown University in Rhode Island.


When and how did you first become interested in planetary science?  How did you focus on the Moon?


Ever since I was a kid in the sixties, I’ve been attracted to space.  I avidly followed the Mercury, Gemini, and Apollo programs.  I always knew that I wanted to get into space somehow.


I came to planetary science quite late.  My initial thought, watching the space program as an enthusiastic fan, was that it was the engineers who were doing spaceflight.  I figured that if I wanted to go into space, I would have to learn engineering.  So I initially started out in electrical engineering as an undergraduate.


Then in 1971, I watched the Apollo 15 mission.  Dave Scott and Jim Irwin landed near Hadley Rille, on the Moon.  Dave and Jim were both Air Force pilots, not scientists.  However, they were so good and so enthusiastic, and what they did I thought was so exciting, that I was hooked.


So I read a few books.  There were a couple that were quite influential.  One was Tim Mutch’s book Geology of the Moon: A Stratigraphic View.  I read it from cover to cover.  I mean, I just devoured it.  I knew after that that this was my calling.


I changed my major to geology in 1972.  I’ve since learned to love geology on the Earth and I’ve done field work on the Earth, but I approached Earth geology from the Moon.  I graduated from Arizona State University with a B.S. in geology in 1976.


That last semester at ASU, I saw a flyer on the departmental bulletin board announcing that NASA was considering having an intern come out to work at the Jet Propulsion Laboratory on the Viking mission, which was set to land on Mars that summer.  So, I applied.  At the same time, we had a visit at ASU from Ron Greeley.  Because I was a big Apollo 15 fan, I knew Ron’s name.  He had published a paper on the origin of Hadley Rille before the mission.  That was the lava tube/lava channel hypothesis.


I arranged to meet with him and we ended up spending a couple of hours, talking about lava tubes and Hadley Rille.  That afternoon ended with him offering me a job at NASA Ames Research Center working on geologic mapping of Mars.  After I accepted that, I found out that my application for the JPL internship had been accepted.  So I ended up spending half the summer of 1976 at Ames, then I went down to JPL in time for the first Mars landing in July.


That was my crash immersion into planetary science.  After that summer, I went to Brown University and started studying planetary science as a graduate student.  At Brown, I zeroed in on the moon.


After a year, I got my Master’s.  At the same time, Ron Greeley asked me to come work as his research assistant again.  So, I decided to go earn some money.  As it turned out, when Ron had come to ASU, he was interviewing for a job there.  So, I found myself back at ASU in 1978, as an employee.  I figured, as long as I was there, working in planetary science, I might as well go ahead and get a Ph.D.  I was Ron’s first Ph.D. student.


How did you get your first job?


Two years into my Ph.D. career at ASU, the U.S. Geological Survey offered me a job.  I had been in contact with Don Wilhelms, who was the moon guy at the USGS.  He became a great inspiration to me.  Don came up to me at a scientific meeting and asked, “How would you like to come to Flagstaff to work?”


Think about it for a minute.  Here I am a student with a gross income of $5400 per year, and I’m being offered a full-time job at the Survey.  It took me about a microsecond to agree.  Plus, I had always dreamed of living in Flagstaff.


So, I took that job in May of 1980.  I finished my research and wrote my dissertation as a Survey employee, and then joined the Survey full-time in 1984.  I was basically there from 1980 to 1990.


It was difficult to study the moon in the “desert years” of the 1980s, because it was out of favor in that decade.


About 1990, the desert years came to an end for a while.  You became involved in some high-level efforts to plan our future in space.  How did that happen?


In the mid-1980s, there were a series of conferences and workshops dealing with a lunar base, which was largely started by Mike Duke and Wendell Mendell at NASA’s Johnson Space Center.  I went to wave the moon flag.  We thought seriously about the steps we needed to go back to the moon, and about what we might do when we got there.


That effort got energized in July 1989, when President Bush – the first Bush - stood on the steps of the National Air and Space Museum on the 20th anniversary of Apollo 11 and said that we were going back to the moon and on to Mars.  That was called the Space Exploration Initiative.


NASA’s response was the “90-Day Study.”  Objectively speaking, that was not a fumble, but it was perceived as a fumble.  The White House was concerned.  Here was a Presidential initiative that had been announced, and their agency had dropped the ball.  How were they going to recover from it?


At that time, space policy was in the Vice President’s office.  They came up with the idea of getting some high-visibility space celebrity to chair a Presidential commission.  They asked former astronaut Tom Stafford, and he agreed.  This was called the SEI Synthesis Group.


This is another of those fortuitous coincidences.  I was looking to leave Flagstaff.  I had talked to Dave Black, the director of the Lunar and Planetary Institute in Houston.   A few days later he called.  He was involved in the Synthesis Group.  He asked me if I wanted to be involved.


The idea was, we were going to get the best ideas for exploring space from the aerospace and academic communities, and the public.  We were called the “Synthesis Group” because we were going to synthesize those ideas and come up with a “magic architecture” for exploring space.  There was a group of about 30 people – mostly engineers.    I was one of the few scientists.  We received briefings from all the Federal agencies and all the space groups.


Stafford didn’t get the Space Exploration Initiative started, but it wasn’t his fault.  I learned a lot.  I not only learned a lot about the engineering you need to go back to the moon –more than that, there were a lot of policy lessons.


What kind of policy lessons?


For one thing, I finally learned the true significance of Apollo.  I was totally misled about it.  I had thought that it was about exploring space, that Apollo was a great visionary leap.


A lot of people in the space business felt betrayed after Apollo.  They had prepared for a world that didn’t exist.  To show you my naiveté, when I was 13, I went to see the movie 2001: A Space Odyssey, and I thought that was our future.  When the year 2001 came and we weren’t on the moon, a lot of people said, “What happened?”


What happened was, Apollo was not about space.  Apollo was not about the moon.  My little “eureka moment” came when I watched a retrospective on Apollo on TV.  They interviewed Frank Borman.  They asked him,  “Did you feel like an explorer when you went to the moon on Apollo 8?”  He said, “No, I felt like a warrior.”


At that moment the true meaning of Apollo sank in for me.  Apollo was a battle in a war.  It was a stick to beat the Russians with.  It was a national security issue.  People ask, “Why did we stop going back to the moon?”  Well, it’s obvious. When you win a battle, you don’t keep fighting it.


There is value to exploration.  The problem is, you need a political context to make it understandable.   When we went to the moon on Apollo, it was perfectly clear to everyone in Washington why they should vote for it.  We couldn’t let the Russians beat us to the moon.


Nowadays, you get blank stares if you say, “You’re going to let somebody beat us to Mars?”  That shows that there is no political rationale for it.  Fundamentally, that’s why SEI failed.


I was very depressed after the Synthesis Group failed.  I thought, “We’ve done all this work, and it has all been for nothing.”  But on reflection, I think that too was a harsh judgment.  We formed networks.  The people who worked together kept in contact.  I would argue that Synthesis led directly to Clementine.


I had a feeling there might be a connection.  You were the Deputy Leader of the Science Team for the Clementine mission, which orbited the moon in 1994.  That was the first American lunar mission since 1972.


I was in the Synthesis Group with Stu Nozette, of the Lawrence Livermore National Laboratory.  They were looking at possibly flying a Brilliant Pebble around the moon.  A Brilliant Pebble, or BP, is a little spacecraft.  It has eyes, sensors.  It has a brain, a computer.  And it has mobility, a rocket engine to let it go on an intercept path.   It can zero in on a warhead, collide with it and render it useless.  Brilliant Pebbles was one of the Strategic Defense Initiatives [SDI] architectures.


The question was, “If you sent one of these BPs to the moon, could you learn anything about it?”  And the answer was, “Yes.”


The Clementine science team adapted the basic BP sensors to scientific use.  We mapped the moon in multiple colors in visible light and near-infrared.  We turned the lidar, which was a method of determining range to target, into an altimeter for measuring lunar highs and lows.


The legacy of Clementine, that changes everything, is the water.  We did not have instruments on Clementine to look for lunar water.  But we improvised an experiment, the Clementine Bistatic Experiment.


We used the spacecraft’s transmitter as sort of a radio flashlight.  We shined this flashlight into the dark polar regions to see if we could see a glint from any ice.  We then looked for the radio reflections using the 70-meter Deep Space Network antenna on Earth.  In the dark regions of the moon’s south pole, we found an enhancement of the same-sense polarization.  That’s a fancy way of saying it’s like a bicycle reflector glint.  We interpreted it as a sign of water ice.


That interpretation was called into question by some of the Arecibo radio telescope folks.  This controversy went on for two or three years.  We agreed, the debate would be resolved by the Lunar Prospector spacecraft, launched in 1998.  Lunar Prospector looked for concentrations of hydrogen on the surface.  The question was resolved and, yes, by golly, there is water ice in the dark areas at the lunar poles.


You said that this changes everything.  Why?


Because we now have a reason to go back to the moon.  We now have a usable, concentrated resource in space.  We can go to the moon and manufacture propellant for rockets.


Think about it.  What does it cost to lift something off the surface of the Earth?  If you use the Shuttle, it costs tens of thousands of dollars per pound to get something to low-Earth orbit.  But the interesting places are anywhere from low-Earth orbit to beyond the moon.   Going to those places requires propellant.  If you have to lug propellant up from Earth, it makes your mission extremely expensive.  But if you can refuel in space, you can go anywhere in cislunar space – by that, I mean Earth’s neighborhood.


Just like during Apollo, the political rationale might be national security.  Cislunar space contains national security assets.  We could, for example, use routine access to build bigger intelligence-gathering satellites.


There is no way we can lug up from Earth’s gravity well everything we need to go to the planets and live there.  We have to learn how to use off-Earth resources.  The moon has given us a golden opportunity to learn how to do that.


Let’s go back to how the moon goes in and out of scientific favor.  We explored the moon during Apollo, but stopped.  In the 1990s, we explored using Clementine and Lunar Prospector.    Now we’re not exploring the moon.  Why not?


The lunar science issue is secondary here.  Scientists will follow where the grant money is.  Science is a social construct, like all fields of human activity.  The search for life is the high scientific priority right now, and that means we’re sending spacecraft to Mars, because Mars is the one planet we can study which might have life as we know it.  The moon is perceived to be a solved problem, and therefore unworthy of the engagement of top-flight scientific minds.


That might actually be changing.  The moon is suddenly being considered an important object again.  A special group, chartered by the National Academy of Sciences, looked at the whole space science exploration program.  When their report came out, lo and behold, a lunar sample return mission was listed as a high priority item.  A lot of people were surprised.


The reason the moon is now back in favor has to do with the origin of life.  It turns out that there is a serious problem with the very early lunar cratering history.  The question is,  “Did all the craters on the moon form in one cataclysmic impact episode, about 3.9 billion years ago?”  If there was a cataclysm, there was no way it could happen on the moon and not on Earth at the same time.  The interesting thing is, this is around the time when we think life first emerged.  So, people perceive that there’s a fundamental connection between this issue and life’s origin.


It is also important to understand the early cratering history of the moon because we use the lunar cratering chronology to calibrate our geological time scales for all the planets.  If we don’t understand lunar history, that means we don’t understand the history of Mars or the other planets.


In addition to that, Clementine and Lunar Prospector found the biggest impact basin in the Solar System on the far side of the moon.  It is called South Pole-Aitken Basin.  When you couple this with the idea that it’s the oldest impact basin on the moon, and therefore could possibly resolve the cratering history issue—Viola! It comes up a high-priority scientific target. 


And, I saved the best for last, if you do this mission, you can rehearse the techniques of Mars sample return.  Mars sample return is viewed as the culminating robotic exploration mission of NASA’s Mars program.


All these threads have converged to make the moon a high-priority scientific item again, much to the stunned amazement of most of my scientific colleagues.


What was the most exciting of surprising moments in your research?


Finding the ice.  The irony here is, I was the guy who, for most of my career, always said lunar ice as a stupid idea.  I had studied lunar samples.  They’re bone dry.  I always thought the idea that there might be ice at the lunar poles was ludicrous, because the moon has no internal water.  I said, “Well, I know it’s been hit by comets and water-bearing meteorites, but somehow it’s lost that water.”  I just never took it seriously.


Suddenly, I found myself defending this idea that I had attacked.  It was a very surprising discovery to me.  It was the thing I least expected from going back to the moon.


Of course, the final irony is that I think it’s so important.   Not scientifically, though it does have scientific ramifications – it’s a record of the volatile history of the inner part of the Solar System for several billion years.  But, its real significance is, it’s going to open up the space frontier.


Have you had any big disappointments in your research?


I used to tell people that I was sorry I never went to the moon.  One of the reasons I got into this was because I wanted to do what Dave Scott did on Apollo 15.  I wanted to do explore the moon and do geology.  Of course, that’s not going to happen.


But, you know, that’s silly.  I had my moon mission.  When I was working on Clementine, I felt like I was on the moon.  I remember the first data dump.  We had just taken the first images.  I recognized a crater in the first pictures.  It was Nansen, up near the north pole.  And when I recognized it, I felt like I was there.


It’s a very familiar landscape to me.  In my mind, the moon is as real as the world I live in.  Of course, I’d love to explore it.  But I’m doing that.  I do that every time I fire up my computer and look at some new data set, or look at some area I haven’t studied before.


It would have been great to go to the moon and walked on it.  I envy the Apollo astronauts that experience.  But you know, I don’t have many regrets.  I have been able to make a living doing what I love.  If you’re able to say that, you’d better not say that you have many regrets!  That’s very ungrateful.  And I’m very grateful.


What advice would you give to students who want to study the moon?


Don’t let anyone dissuade you.  Everyone told me I was nuts.  In a way they were right.  But to do what you love, you have to be willing to ignore people who tell you that.


Now, when students tell me they want to do what I do, I say, “Well, you’re not going to find a job—there’s no future—there’s no growth.”  If they say, “Okay” and wander off, they flunk the first test.  They’ve got to look me in the eye and say, “I’m going to do it anyway.”  A couple of students have done that, and they’re now in the lunar science business.


Find something you love and do it.  If you really love it, chances are you’ll be good at it, and you’ll be able to figure out a way to make a living doing it.




Postscript:  This interview was conducted in late 2002.  A little over a year later, President Bush announced our nation’s return to the Moon with his Vision for Space Exploration.  I had the honor to serve on a commission he assembled to advise on the implementation of the Vision.  We have determined that not only is lunar polar ice an enabling asset, but the near-constant sunlight of the poles offer both a power source and a benign thermal environment, making the lunar poles our first destination for a permanent outpost on the Moon.




Spudis Lunar Resources was created by renowned planetary geologist Paul D. Spudis (1952-2018) and is archived by the National Space Society with the kind permission of the Spudis family.

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