Sean Solomon has served as the director of Columbia University’s Lamont-Doherty Earth Observatory since 2012. Much of his recent research has focused on the geology and geophysics of the solar system’s inner planets. He was the principal investigator for NASA’s MESSENGER mission, which sent the first spacecraft to orbit Mercury and study the planet’s composition, geology, topography, gravity and magnetic fields, exosphere, magnetosphere, and heliospheric environment.
The beginning of Solomon’s research career coincided with the birth of a new field — planetary science. This month, in celebration of the 50th anniversary of the Apollo 11 lunar landing on July 20th, he will be participating in a panel discussion entitled “Small Steps and Giant Leaps: How Apollo 11 Shaped Our Understanding of Earth and Beyond.” The event is co-sponsored by the American Geophysical Union (AGU) and the National Archives. Other participants will be AGU leaders, including AGU president Robin Bell, and several early- and mid-career planetary scientists.
At what point were you in your career when Apollo 11 landed the first humans on the Moon?
I was a graduate student at MIT, and I was doing a thesis in seismology. However, I had written a paper about the interior structure of the Moon before the Apollo 11 mission. MIT faculty and students were holding discussions about the Moon in advance of the Apollo 11 landing, so we were primed to think about the impact of the mission’s findings.
How did the Moon landing affect you personally?
I was glued to the television set watching the landing and the Moon walks like everybody else. It was a singular event in history for humans to walk on another planetary body. It captivated everyone. The landing and Neil Armstrong’s first steps onto the lunar surface were watched, I would guess, by billions of people on this planet. So, it was a great event for the world's population to come together and marvel at a profound technological achievement.
In terms of my own work, the mission led to an explosion of new data about the Moon. I included lunar work in my research agenda for a number of years thereafter, using data from all of the Apollo missions, from the findings of sample analyses to the observations from the orbital and surface experiments that Apollo carried.
How did this mission affect the scientific community as a whole?
There was really no field of planetary science in 1969, just a handful of people who called themselves planetary astronomers and studied other worlds through telescopes or with theoretical work. NASA had sent spacecraft to Venus and Mars by the time of Apollo 11, so there were a few people who were working on planetary data, but the space age was less than 12 years old at the time of the first Moon landing. Almost everybody who worked on the scientific return from the Apollo program came from other fields — earth science, chemistry, or physics — and they became lunar scientists. NASA’s investments brought in huge numbers of scientific experts and funded new instruments and labs across the county to create a lunar community that hadn't been there before.
It's also important to remember that nearly coincident with the Apollo program was an explosion of robotic missions to explore other parts of the solar system. Within a few years of Apollo 11 we had launched spacecraft to fly by Mars, Venus, Mercury, Jupiter, and Saturn. It was an enormous expansion of our presence in space that was enabled by a healthy NASA built up to conduct the Apollo missions but an agency that also had the budget and the engineering expertise to figure out how to explore the rest of the solar system by spacecraft. The field of planetary science came into its own in those few years after Apollo.
Can you tell me a little bit about Lamont's involvement with Apollo 11?
Lamont was very heavily involved in the Apollo program and was much more active in planetary research than it is now. There were Lamont scientists who were in line to receive some of the first samples brought back from the Moon. At least equally importantly, Lamont was a leader in the geophysical exploration of the Moon. Over the course of the Apollo missions there were several geophysical experiments, but the one that spanned nearly all of the missions was the passive seismic experiment. And several early Lamont seismologists had teamed together to put that experiment on Apollo, including Maurice Ewing, Frank Press, Gary Latham — the principal investigator — and other team members from Lamont as well.
In later Apollo missions, astronauts measured the heat flowing out from the lunar interior. The Apollo Heat Flow Experiment was led by Marcus Langseth, a Lamont scientist for whom our current research ship is named. Also, during the Apollo 17 mission, there was a gravimeter that was mounted on the astronauts’ rover to measure the variation in lunar gravity over the course of the rover traverse. That experiment was led by Manik Talwani, who by then was the Lamont director.
Ewing was studying seismology in the ocean basins before he was contacted by NASA. How does that relate to studying seismology on the Moon?
Ewing pioneered the use of seismology to study the crust beneath the oceans. He took seismic experiments to a venue where there had never been such experiments before. And with them he showed that oceanic crust is different from continental crust. So when he had the opportunity to send a seismometer to the Moon, it was another chance to make seismic experiments in a new place, just as he had done in the oceans, and he was sure he'd learn something new.
Why is learning about the Moon so important to us?
Landing humans on the Moon and bringing them back safely was a formidable technological challenge. And the time within which that was accomplished was incredibly short. The first human spaceflight was in 1961. Kennedy's speech announcing that we would go to the Moon before the end of the decade was in 1961. Within only eight years we not only figured out how to send humans to the Moon and get them back, but we actually did it. That was the first time in human history that a person set foot on another planetary body. It’s something that will never happen again.
Apollo also provided our first detailed look at another planetary body. And it showed us how special the Earth-Moon system is. It was the Apollo 11 mission that demonstrated convincingly for the first time how ancient the Moon is — the samples brought back were more than 3 billion years old. We learned that the Moon recorded and illuminated a period of solar system history that we hadn't begun to appreciate through our study of Earth. There's no rock record on Earth for the first half billion years, but there is on the Moon. And because the Moon is our satellite, it's part of our history, too. We learned how violent and chaotic the earliest history of the solar system was. We wouldn't have gained that perspective without leaving Earth.
How do you think we were able to send humans to the moon so quickly?
As a nation, we put a big priority on meeting the goal that Kennedy set out. And throughout most of the 1960s we had Democratic presidents, Kennedy and Johnson, who were supportive of that program. In the 60s, the funding was there, and America's reputation was at stake. There were military implications to the control of space. We were in the middle of the Cold War. There were many reasons we put the resources behind the Apollo program. NASA was a pretty daring agency at that time. They were willing to take risks. They didn't want to risk more human lives than they needed to, but the astronauts were putting their lives on the line. The first astronauts were test pilots, who risked their lives every day over the course of their work; they knew what the risks were. NASA was a different agency back in the 60s than it has been since. Their engineers and managers set their sights high and did what they needed to do to meet schedules. And they had the resources to do it.
How have lunar missions changed from the time of Apollo 11 to present day?
When the Apollo program was underway we were sending two missions a year to different parts of the Moon. There was to have been an Apollo 18, an Apollo 19, and an Apollo 20, but these were expensive missions, and in 1972 the U.S. was spending a lot of money fighting the war in Vietnam. Those missions were cancelled, even though all of the hardware had been built and the astronauts that would fly those missions had been selected, and that decision ended the Apollo program. It was a challenge to devise experiments that could build on Apollo’s legacy and yet be done inexpensively with robotic spacecraft, which were being sent to many other targets — Mars, Venus, Mercury, Jupiter, Saturn, and, a few years later, Uranus and Neptune.
NASA did not return again to the Moon until the 1990s, with the Clementine orbiter — sponsored jointly with the Ballistic Missile Defense Organization — and the Lunar Prospector orbiter. Ten years ago, NASA launched the Lunar Reconnaissance Orbiter, which is still operating at the Moon, and other missions have followed. Space organizations in other countries have also launched lunar missions, including the Soviet Union prior to and even after the Apollo missions, and later Japan, India, China, and Israel. In the U.S. and abroad, there are commercial entities that have their sights set on lunar landing. And earlier this year NASA announced plans to send the first woman and the next man to the Moon by 2024. If that goal is to be met, partnership with the commercial sector will be needed.
What do you hope the takeaway of the reignited interest surrounding the Moon landing will be?
I hope for two takeaway messages. First, the Apollo 11 mission was not only a remarkable technological achievement in the history of our species, but it also marked a “giant leap” in our appreciation of Earth’s place in our planetary system. And second, the Moon today still holds answers to important questions about the early history of our planet, and there remain myriad scientific as well as political and commercial reasons to return.