Interview with Prof. Clive Neal

Clive Neal
Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame
Ph.D, University of Leeds, United Kingdom, 1986
B.S., Geology, University of Leicester, United Kingdom, 1982
Postdoctoral Research Associate, University of Tennessee, Knoxville - 1986-1990
Assistant Professor. University of Notre Dame. 1990-1996
Associate Professor. University of Notre Dame. 1996-2007
Professor. University of Notre Dame - 2007-Present

Summary of Activities/Interests

Professor Neal's petrologic research uses a technique of crystal stratigraphy to explore lunar (mare) basalt and impact melt evolution. Crystal stratigraphy involves using quantitative petrography (in the form of crystal size distributions or CSDs) to evaluate the size distributions of different phases. This can identify different crystal populations that can give information on the samples' petrogenetic history. The CSDs guide the analytical phase of the investigation to different populations. Individual crystals are then analyzed by electron microprobe for major and minor elements, and by Laser Ablation ICP-MS for trace elements. Zoned crystals contain a wealth of information regarding sample history that the crystal stratigraphy approach can unlock.

Lunar Science Professor Neal's lunar research consists of two major thrusts: 1) Lunar Petrology; and 2) Lunar Geophysics.

1) Lunar Petrology: Research in this area is examination of melt rocks, both natural basalts and impact melts. Current projects include investigation of the petrogenesis of Apollo 12 and Apollo 17 mare basalts as well as the Apollo 14 and Apollo 16 impact melts, both using the crystal stratigraphy approach. Melt inclusions are also being analyzed to explore the petrogenesis of the Apollo 12 basalts.

2) Lunar Geophysics Professor Neal is the Principal Investigator on a proposal to NASA to send two landers to the lunar surface, each carrying a sophisticated geophysical instrument package. The science rationale for this mission is that we know very little about the interior of the moon, despite five seismometers being deployed on the lunar surface by Apollo; the small footprint of the Apollo network meant our knowledge of the deep interior would be limited. Each lander on the "Lunette" mission will contain a broad band and short period seismometer, two heat flow probes, an electromagnetic sounding experiment, and a laser retroreflector. The proposed mission is an international collaboration involving the USA, France, Germany, Japan, Switzerland, Austria, and Italy. The nominal mission will last four years.

Interview of Professor Clive Neal, University of Notre Dame

1.To begin with, can you tell us your interesting story of journeying from Leeds to Notre Dame all because of the Moon?

During my undergraduate degree at the University of Leicester, UK, I became really interested in mantle petrology. That led me to apply for a PhD studentship to work with Prof. Peter Nixon at the University of Leeds, UK, to work on kimberlite-like intrusives in the Solomon Islands, SW Pacific. In. fact, undertaking the fieldwork in the Solomon Islands was the first time I had actually flown anywhere and it was from London to Sydney, Australia! That study led me to apply for a multitude of post-doctoral fellowships in the United States, but at the end of 1985 the only offer I had was a temporary lectureship for one semester, at the University of East Anglia, UK. While there, I received an offer from Prof. Larry Taylor at the University of Tennessee, Knoxville, for a 2-year post-doctoral research fellowship, which was amazing because I had never applied to the University of Tennessee! I had come in second for a post-doc with Prof. Mike Drake at the University of Arizona and Larry needed a post-doc quickly and Mike gave Larry my CV. This post-doc was primarily focusing on mantle petrology with about 20% focused on Apollo samples. This was my introduction to the Moon. I arrived in Knoxville on July 2nd , 1986, and immediately fell in love with lunar petrology and all things to do with the Moon. While my intention was to return to the UK after my post-doc to go into academia, the Prime Minister at the time, Margaret Thatcher, had experimented with UK universities and reorganized geology into centers of excellence for research and teaching. I wanted to do research but the positions were very few and this was before the age of the internet so I was relying on seeing position advertisements in nature, Eos, etc. Basically, my route back to the UK was switched off. Larry extended my post-doc for another 2 years and I eventually got a job at the University of Notre Dame, where I have just completed my 32nd year. 

2. Of course, I asked this because many scientists and engineers have been a part of such "brain drain" movement. Do you think this is why the USA is so successful in science and technology?

Being accessible to new ideas from multiple sources makes for robust science and exploration in science/technology programs. The United States has offered me more opportunity in space science and exploration than the UK ever could, so I would say “yes” to your question. I would also say that the United States has been very welcoming to me and now as a U.S. citizen, and I have made it my home. 

3. Science is global and this is why outstanding scientists tend to congregate at places allowing ideas to flourish and cooperation to take place. You have mentioned many times that for lunar science to sustain it must be international in nature. Can you elaborate a little on this point?

I would say that for lunar science AND EXPLORATION to be sustainable, the world must go forward together. Remember – science enables exploration and exploration enables science. From what we have learned about the Moon and now with aspirations to have human permanence (as stated in the current U.S. Space Policy), no one country can afford to do this on their own. For example, lunar resources have been called out by NASA as key for a sustained/continuous human presence on the Moon, and as being foundational to stimulating a vibrant cislunar economy. However, we do not know if the resources we know are there in sufficient quantity and can be extracted, refined, and used economically – basically the term “resource” has been used when “reserve” is what is meant. And while a number of missions are scheduled to examine the poles for volatile deposits, no coordinated lunar resource prospecting campaign has been devised and implemented to show if these resources are reserves. This has to be international in nature because the Moon is, in fact, large. For example, Brown et al. (2022 – Icarus 377, Article 114874) used 10 orbital datasets to define the top ten best permanently shadowed polar regions for containing water ice, and this covers an area of >6,000 km2! That is a lot of real estate to cover and no one country/agency can do this effectively.Therefore, this campaign is perfect for international collaboration, cooperation, and diplomacy in an era that so desperately needs this! 

4. What are the most important lunar science projects to be carried out within the next decade to prepare for human settlement on the Moon?

Two projects stand out, at least for the U.S. view point – returning samples from the South Pole – Aitken Basin to try and get an age of the basin, and establishing a long-lived, globally distributed geophysical network to understand the internal structure (as the Moon preserves the initial differentiation of terrestrial planetary bodies via a magma ocean). In addition, the global datasets that we now have of the Moon have indicated important areas for sample investigations, either in situ or via sample return. Sample return produces the “gift that keeps on giving” as seen by the Apollo 15 and 17 volcanic glasses, collected on the Moon in 1971 and 1972, respectively, but it wasn’t until 2008 that it was shown these were derived from a relatively volatile-rich source. This discovery changed our view of the Moon! So more samples from targeted areas (e.g., the silica-rich Gruithuisen Domes) will enable many decades of scientific investigation, if the samples are in the kilogram quantities and are properly curated. 

Perhaps the most important scientific project is how the human body tolerates one sixth gravity and the radiation environment. We have no data regarding how humans will react to living in partial gravity. We have a lot of data regarding how microgravity adversely affects the skeletal structure and the muscle system, so sending humans to Mars will be challenging. Is one sixth gravity enough to reverse bone density loss and muscular atrophy? This could be enabling for developing a Mars transportation system but we need humans on the Moon for months and years in order to understand this in sufficient detail to make definitive conclusions. 

5. What is your vision of lunar science and exploration in the longer term, say, 20 years from now? How big a part would international cooperation play in this endeavor?

As noted above, the most immediate need is a coordinated international lunar resource evaluation campaign. If we start with polar water ice and show the resources are, in fact, reserves and space agencies commit to human permanence on the Moon, a market for life support consumables and liquid oxygen-liquid hydrogen rocket fuel will become available. This could bring the Moon into our economic sphere of influence and generate new jobs and new technologies that would show human space exploration has a direct benefit to society here on Earth. THIS is the way to make human space exploration sustainable – by showing it benefits society here on Earth. 

The coordinated international lunar resource evaluation campaign also benefits multiple stakeholders as shown in the figure to the left. The basic data (green text) will inform science, exploration and commercial activities and represent the majority of the data that should be returned from any lunar prospecting mission to explore polar volatiles or any other lunar resource. Such a campaign is enabling for many new scientific investigations, developing human exploration architectures, and business plans for commercial companies. 

6. You have good contacts with the Chinese lunar researchers, sometimes, better than among themselves, I think. Do you have any scientific advice or suggestions to them and to the lunar and deep space exploration program as a whole? Do you see room for building up international cooperation? 

My advice to the Chinese lunar scientists is to keep communication and data sharing open. The Lunar List Serve (known as the Lunar-L) that I run has almost 1100 subscribers worldwide, many of whom are from China. This email list serve allows information regarding lunar science and exploration to be shared easily and quickly. By regularly communicating and sharing data trust can be built up and collaborations can be established. So, I would say that as humans strive to become a multi-planetary species, cooperation and collaboration are the key to success. In taking our first steps out of this planet in the 1960s and 1970s, it was done in a spirit of competition and once that competition was won, the program lasted less than four years. The International Space Station has been conducted in a spirit of cooperation and has been going for over 20 years. I hope this new focus on the Moon will allow cooperation and diplomacy to prevail and that we can go out into the Solar System as a species rather than as individual countries. 

7. The guiding principles of ISSI-BJ are to be a neutral platform in promoting excellent space science research via international cooperation. Sometimes it is easy to do so but sometimes (like now because of the COVID-19 pandemic and some other factors) it is not. Any wise words on how we can do better, perhaps, with your help?

I applaud and fully support ISSI-BJ for following cooperation, given my comments above. But I truly believe that in-person meetings are better than Zoom meetings for developing relationships, trust, and serendipitous collaborations through informal discussion over coffee breaks and dinners. I hope that in the future there will be an opportunity to have an in-person “Space Exploration Summit” where an international array of space exploration enthusiasts (from government, industry, and academia) can meet and discuss potential collaborations. Facilitating cooperation is essential as we move forward together to better understand our Solar System and become a multi-planet species. 
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