Rosaly Lopes, Geologist and Planetary Volcanologist

Volcanoes offer a unique lens through which to consider a foundational question in planetary science: in what ways is Earth truly unique in our Solar System and in what ways is it just another planet? One of the most fantastic discoveries of the Voyager Mission was its detection of active volcanism on the surface of Io, one of Jupiter's inner satellites. It was the first confirmation of volcanic activity outside Earth, and it offered tantalizing clues on the function of geological systems and the formation of planets and satellites. Rosaly Lopes joined JPL one academic generation after the planetary encounter phase of the Voyager Mission, and her research has been foundational to the study of volcanism on Earth, Io, and beyond.

Born and raised Rio de Janeiro, Lopes always gravitated toward science, and she pursued her first interest in Astronomy at University College London. Toward the end of her studies, she took a planetary science class and promptly switched focus for graduate school on a comparative approach to volcanology on Earth and Mars. In 1989 Lopes joined the Jet Propulsion Lab at a time when women in senior scientific positions remained in the distinct minority, and in the discussions below she reflects on the changing, more balanced demographics at JPL and the many benefits this has conferred to the Lab. Her first major mission assignment was on the Near Infra-red Mapping Spectrometer (NIMS) team for the Galileo Mission, which led to the discovery of over seventy new volcanoes on Io. Lopes followed this work by focusing on synthetic aperture radar capabilities for the Cassini Mission. She worked extensively on the study of cryovolcanism on Titan, a major satellite of Saturn.

As an energetic communicator of science, Lopes has appeared in science documentataries, she is the author of numerous books and articles geared toward popular audiences, and she has lectured around the world with specific interest in encouraging underrepresented groups to consider pursuing careers in science. Her numerous awards include the Carl Sagan Medal given by the American Astronautical Society and the NASA Exceptional Service Medal.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, June 9th, 2023. I am delighted to be here with Dr. Rosaly Lopes. Rosaly, it is wonderful to be with you. Thank you so much for joining me.

ROSALY LOPES: Thank you.

ZIERLER: To start, would you please tell me your title and affiliation at JPL?

LOPES: I'm the Deputy Director for the Planetary Science Directorate.

ZIERLER: Organizationally, tell me about the Planetary Science Directorate. Where does it sit, who do you report to, and who reports to you?

LOPES: Where we sit is, JPL has a director, a deputy director, and then a number of what we call "directors for." Planetary Science is one of those directorates. There is Earth Science; there is Astrophysics. Then there is what is called Engineering and Science Directorate, and that is where actually most of the technical staff are. That has the majority of the Lab's population. In my directorate, I'm the deputy to Matt Wallace. The people who report to us are senior people, and they are senior programmatic managers, managers of, for example, Formulation of future flight projects, implementation. We are responsible for all the Planetary Science projects. We meet every week, let's say, with the project manager for Europa Clipper, and the project manager for Psyche, etc, particularly for the missions in development. We meet with the Formulation leads, an office that is essentially responsible for preparing proposals for competitive missions like NASA's New Frontiers and Discovery programs. We meet with the manager in charge of missions that are in operations. We are essentially responsible for the missions, the planetary missions, in formulation, implementation, and operations.

ZIERLER: On any given day, how much time do you have that you can devote to science, and how much are you working in administrative and managerial affairs?

LOPES: I don't have a lot of time for science these days. Mostly, since I took this position in March, the science I am doing, and I am still doing some, is as a co-I or collaborator. Somebody else leads the project, and I collaborate, I advise, I do small parts of the project. I've got way too much responsibility and way too much on my plate. It was a choice. In my previous position, which was as Directorate Scientist, that was a half-time position, so I had more time to do science. On the other hand, the JPL director asked me to take over this position, and I thought it would be good for me, and hopefully good for the Lab and for my directorate. I really love JPL and I try to do my part, what's going to be most useful.

ZIERLER: As a woman scientist at JPL, you've been there so many years, what has changed over the years, particularly in the light of the historic decision with Laurie Leshin, of course, being named the first woman director of JPL? What does that mean for you? What does that mean for JPL?

LOPES: The change I have seen is that we have many more women in science. Let's say that, in my generation, the number is much greater than that for my colleagues in previous generations. It was inevitable that eventually that we would have a female JPL director. What I see is that for any job, you need a candidate pool you can choose from, and of course if you have 50 candidates and only one of them is a woman, unless she is absolutely exceptional, the odds are that you're not going to choose a woman. But now, we probably have maybe a third to half of the candidates being women for high-level positions. I was helping to interview for a position recently, and most of the candidates were women. We down-selected and interviewed two women. If you have the candidates there, it's going to happen. Nevertheless, I think it's really good for the morale of the Lab to have a female director. I think Laurie Leshin is exceptional. She is an exceptional communicator, and she's very likable. She gives you this feeling that you want to work harder because you want to help her. That quality of leadership is amazing, is inspiring. I think she was absolutely the right choice. I'm very happy that she was chosen. I think it was going to happen eventually just because you have more candidates in the pool.

ZIERLER: There are so many exciting missions that are going on now at JPL. What are you most closely involved with? What are you most looking forward to, in terms of future discovery?

LOPES: The only mission I'm a co-I on at the moment is JUICE, the European mission to Jupiter. But I also collaborate with one of the teams on Juno, and I'm very excited about Europa Clipper even though I'm not part of it. I think that that is going to be an amazing mission. Also, Psyche. I think Psyche is going to be so interesting, going to this largely metal asteroid. How did it form? How did it get that way? What are the features we are going to see on the surface? What I do, my expertise, is in planetary geology, and just imagining what the surface of Psyche is going to look like, it's really mind-blowing. Europa, we are going to find a lot of interesting things, but—we've been there. We observed it with Voyager, with Galileo, so it's more like we know what we're looking for. With Psyche, it's still an unexplored, mysterious object, so I find that really fascinating.

ZIERLER: For your own science, is it more appropriate to think of yourself as a volcanologist who does geology, or a geologist who does volcanology?

LOPES: Strangely enough, my first degree is in astronomy, so I'm kind of like neither. [laughs] My PhD was in the planetary geology and volcanology area. I have done some work on terrestrial volcanology. I would call myself a planetary volcanologist. I think that would be the closest.

ZIERLER: What aspects of your work are terrestrial and where are you really focused on other planetary bodies?

LOPES: It has evolved over the years. I used to do more terrestrial. I always did some planetary, but I did some more terrestrial, and then it kind of evolved to being mostly planetary. I have collaborated, co-authored, some papers on terrestrial volcanology, but I would say that my main emphasis is planetary. When I joined the Galileo mission and I was studying Io, it was very Io-focused and there was an element of comparison with lava lakes, especially, on Earth. So I did more terrestrial. Then I moved onto the Cassini mission, with the radar instrument and studied Titan. Titan doesn't have active volcanoes that we know of. It has some features that—I actually did a lot of that work, argued—are cryovolcanic. On Titan, I went more towards the overall geology, probably with somewhat less terrestrial, but we always worked with people who had the terrestrial geology expertise, and were on the team, so that we can use each other's expertise. I am very much a team player, and I love to work in teams, and I love to collaborate with people, very different perhaps from many university professors who perhaps want to just do the papers by themselves, or perhaps with one graduate student. I like team papers. I have led some papers with an enormous number of coauthors.

Broad Perspective on Planetary Volcanology

ZIERLER: With your dual expertise in geology and volcanology, to the extent that there is a generality of geology—you can look at an entire planet—whereas there might be a specificity with volcanoes—they only exist in certain places—are there things about volcanoes that you can learn generally about geology, and vice versa, are there things specifically about geology that you can only learn from the perspective of looking at volcanoes?

LOPES: Of course all of the geology related to volcanoes, you have to look at the volcanoes and focus on that. But volcanoes actually, or some aspect of eruptions, have occurred on really all the terrestrial planets. We have a lot of wht we call terrestrial planets that also include moons—Mars, Venus, Mercury, Earth's Moon, Io —you find volcanoes everywhere. Volcanoes are the main way that a planet will lose heat. Something that has happened during my career that is really fascinating is the discovery of cryovolcanoes, in ice worlds, you actually have oceans of liquid water under the ice crust, and the liquid water, sometimes mixed with other things, maybe ammonia or methane or whatever, can erupt, or has erupted in the past. That's cryovolcanism, which is essentially the same process as magmatic volcanism. You even end up with similar landforms. But between all these various moons, like Europa, Enceladus, many of the others, these have had volcanism or cryovolcanism in the past even if they don't have it anymore. There are a lot of examples in the solar system. The Earth is like our comparison basis. For example, using various thermal signatures on volcanoes on Io, I proposed that these volcanoes are lava lakes. Why? Because I compared them with the thermal signatures of lava lakes on Earth, and I brought in a terrestrial volcanologist to help in that work. Cryovolcanoes are a lot more different. The process of bringing material from the interior to the surface is volcanism, but cryovolcanism is certainly different. It's challenging, how exactly we get that material to the surface, when the density contrast is such that the liquid water is actually denser than the ice crust. People think a lot about that, because we see it happens, and it has happened. Would lava lakes form on cryovolcanoes? Well, not that we know of.

ZIERLER: As you mentioned, it seems like it's a two-way street for you—that what we know about geology and volcanology on Earth is valuable for other planetary bodies; and vice versa, we can learn about Earth from studying other planets.

LOPES: Yes, exactly. In fact, there are various aspects of research in volcanology that were actually helped by planetary data. For example, for most planets, this is true. You have data with the camera, morphological data. In the early days you didn't have any kind of compositional data, so people would try to relate the shapes of volcanoes and lava flows or lengths of lava flows to parameters such as effusion rate and composition. That's not something that terrestrial volcanologists would do. If you wanted to figure out the composition of a volcano's lava, you just went there and took a sample. Now, with planets, you couldn't do that. What we can do is still very limited. Bringing back samples is very expensive. It's difficult. So we had to create several other ways, looking at morphology and then developing instruments for planetary missions like spectrometers that would tell you about the composition. Yes, it's a two-way street. It's not just in volcanology; in planetary geology in general, there are a lot of questions that we start asking when we look at other planets. For example, why is the Earth the only place where we have plate tectonics? It's not really my expertise, but it's kind of like, is it because if the crust is too thick, then the plates can't break, cannot create plate tectonics? Or do we need a certain ratio of the size of planet and the thickness of the crust? Do we need water for plate tectonics? All these types of questions.

A great example how planetary geology helped us understand the Earth is impact craters. People used to look at the Moon in the 1960s and look at those craters and say, "Oh, they're volcanic craters," because they were comparing with the Earth —the craters we knew on Earth were volcanic. Then people like Eugene Shoemaker studied Meteor Crater in Arizona that was a suspected impact crater, and not only he showed it was an impact crater, but he showed some characteristics that impact craters have. That not only changed our understanding of the Moon, that, "Oh, wow, this body is just covered with impact craters," but then we started asking, "The Earth must have had a lot of impact craters in the past, but the Earth had erosion, had plate tectonics, so it was difficult to recognize them." Then people started looking at the Earth with satellite images and doing fieldwork, and now we know of a lot of remnants of impact craters on Earth. It's a two-way street, yes.

ZIERLER: Are you involved at all in biology issues, either origin of life questions on Earth, or astrobiology, the search for life beyond planet Earth?

LOPES: In a peripheral way, in astrobiology, because I am leading a project on Titan, which is for NASA's Astrobiology Institute (NAI). Mine was actually one of the last proposals to be selected in the NAI program, in the NASA Astrobiology Institute. I am good at organizing teams and leading teams, so when a call for those proposals happened six years ago or so, some colleagues of mine said, "Rosaly, why don't you lead a proposal on Titan?" I said, "But I'm not an astrobiologist." They said, "But you know about Titan." So, I put a team together, and we won the proposal. There are biologists in the team, there are chemists, there are people with all this diverse expertise. I really like that. I really like working with teams, and large teams, and putting those things together. One of the things that the biologists are doing is experiments with various bacteria to find out if they can survive under Titan ocean conditions, what can survive at the high pressure and low temperatures we might find at the ocean. Then, we have chemists finding out about the atmosphere, what's the chemistry of the atmosphere, which chemicals we're going to find on the surface, how do they get transported on the surface. How do they get into the ocean? Can these chemicals alter the chemistry of the ocean? Do we have enough, quote, "food" for any life that we might have in the ocean? Then, if there is life in the ocean but we can never detect it, then it's not much use to us. That's where the part of cryovolcanism came in—can we get the ocean material to the surface to be detectable? How would the biosignatures appear on the surface and the atmosphere? It's a really very complex project, and we're not at the end of it yet, but that is an example of—I seem to have made a career out of getting involved in things that I really knew nothing about! [laughs] And, as soon as I get comfortable in an area, then something happens and I'm forced to go to another one!

ZIERLER: The historic connections between JPL and Caltech, has that been an asset for you? Do you have opportunity to collaborate with Caltech professors? Can you ever serve in a mentor capacity to Caltech students?

LOPES: I really like the fact that we're connected to Caltech, and there are things we can certainly do with Caltech scientists. Actually, I have in this team, the Titan team, I have a collaborator at Caltech, and one of his former graduate students has been at JPL for many years and he's deep in this project. But Caltech and JPL are pretty different institutions, so sometimes it's hard to find that opportunity to collaborate. We have certainly had Caltech professors in our spacecraft teams, and we have had JPL researchers not only in science, but technology as well, collaborating with Caltech professors. It would be good to have more collaborations. I think there are some challenges because the cultures at the institutions are pretty different. JPL is a very teamwork-oriented environment, and Caltech tends to focus more on the individual research and the individual research contributions. It's really two different beasts.

Focus on Solar System Satellites

ZIERLER: I wonder if you've ever thought about the road not taken, if you had become an academic professor. Would the kind of science that you've done at JPL, do you think that would be more or less what you would have pursued as a professor, or do you think it's entirely dependent on the opportunities, what's available to you at JPL?

LOPES: Oh, I think that it would probably have ended up quite different. I have taken advantage of JPL opportunities which I wouldn't have had as an academic, necessarily. For example, when I came to JPL, I was working on Mars geology and volcanology, still with Viking data, because we hadn't been back to Mars. Back then there was more terrestrial work as well, more theoretical work, so that was more in the academic line. I wanted to stay at JPL because I love flight projects, and that is what I have always wanted to do in life, is to work for NASA. I saw being a scientist as a path to working for NASA. If I could have become an astronaut, I would have done that. [laughs] So, I came here, and then I met people who were working on the Galileo NIMS—which is the Near Infrared Mapping Spectrometer—team on the Galileo mission. At that time, there were no missions going to Mars, and they gave me this opportunity. They said, "You do volcanology, and we need someone to lead the Io observations." Observation planning and science planning. So, I became what was called at the time in the project a science coordinator. These days it's called like an investigation scientist. I came in like through the back door, because the PIs and the co-I's had already all been selected. I was planning and designing observations. But people at JPL are really good at finding talent, identifying talent, and then giving you opportunities, so I quickly got put on more helping with the research part, and I taught myself a lot about Io infrared spectroscopy. I told the PI at the time, "I don't know anything about infrared spectroscopy," and he said, "Oh, don't worry, you'll learn." So, I had to learn that field, at least enough for me to get by. [laughs] When the data came, then I analyzed the data, and I started writing papers, and they gave me completely free reign. I ended up doing the work of a co-I, in fact I think a lot of people didn't realize that I wasn't a co-I. I did press conferences and led papers, but it was thanks to the PI, largely, Bob Carlson, who passed away not long ago, who gave me that opportunity. Then I had this great time on Galileo analyzing Io data and writing papers and all that, and I then became known as an Io volcanologist. I was a Mars person before. Then Galileo was coming to an end, and while if I had been an academic, I might have stayed on, researching and mining everything out of those data, but it would have been probably kind of diminishing returns. But I had to find a new position, because here, we are essentially on soft money. I had to find money for my salary. Talking to one of the Galileo NIMS co-I's, a very famous guy called Larry Soderblom, he said, "You should join the Cassini radar team. They need help." I said, "But I don't know anything about radar," and he said, "Oh, don't worry. You'll learn." [laughs] So that's the story of my life.

ZIERLER: There you go! [laughs]

LOPES: "There you go again, jumping in at the deep end" I thought. I contacted the team lead. Actually the team lead really was Charles Elachi, who was director of JPL, but his deputy was essentially acting as the team lead—Steve Wall—and I contacted him. He said, "Yes, our investigation scientist wants to retire, so talk to him." That guy was called Ladislav, or Laci Roth, who was from Slovakia initially. It's one of the great things at JPL; there are people from all over the world you work with. He helped me a lot to understand radar, so I got into that role. Again, it was a back-door way, because the team members had already all been selected. But I quickly—again, they recognized what I could do, and I started writing papers, and I took the part of cryovolcanism, and then geologic map of Titan. I became really happy in my Titan world. But Cassini finished. Actually, I had quite a nice long run with that mission, but Cassini finished, and even before it finished, it was kind of like our funding was diminishing some. To give myself other options, I actually, around that time—I think it was even before I joined Cassini—I became a group supervisor, so I had a management position but a small one. It was a one-day-a-week kind of thing. Then, while I was working on Cassini and Cassini was winding down, I became a deputy section manager and then a section manager. So, I have line management experience, as we call it at JPL. All of that is useful, all of the experience you acquire is useful. I don't know if it's a natural tendency but I tend to sort of organize teams, so on both on Galileo and Cassini, I became kind of the de facto sort of deputy, like a team lead. That all helped me a lot when I put this big NAI proposal together for Titan. Then, I really wanted to give up section management, because it was sucking a lot of my time, and I didn't enjoy it as much as some of my other positions. It's kind of like a position where you have a lot of responsibility but you don't have a lot of authority [laughs], if you know what I mean. I thought, "Well, I want to step down" after a few years in that position. I won the NAI, which gave me funding to be able to step down.

Also JPL was very nice to me and I got a position as editor in chief for Icarus, which is a major planetary science journal, and they paid for my time so I could do that as a JPL assignment, let's say. That was also very useful experience, being an editor. All through my career since my early days at JPL, I was writing books. I just published another one. I think it's number ten [laughs]. I'm a good editor. I think I'm a good writer. We all have different talents, and part of what each of us has to do is recognize where are strengths are. I liked that, being a journal editor, and I did it for three years. But then there was an opportunity to become the directorate scientist, or directorate chief scientist as it was called then, for Planetary Science, for the Planetary Science Directorate. In fact, the person who was in that position was a co-investigator on my NAI Titan project. He was also a Titan guy, and he suggested to me that I should apply. He must have put in a good word, because I got the job. He retired from JPL and went back to France. He's still active in research.

I had that opportunity, and so I moved into the Directorate, which is different than the science division where I was working before. I moved during the pandemic. I had no transition time, because my predecessor, Christophe Sotin, was in fact already in his hotel room, getting ready to fly back to France the next day, when my selection was announced [laughs]. We had a phone call that evening. I knew certain parts of the job, and he's a very nice person, and we had some meetings over Webex while he was in France, but it was very hard to come into a new organization where I knew some people but not everybody, during the pandemic. It's hard when you can't go next door and ask somebody something, figuring out various procedures, and who is who, and what people did. I have it in my resume the date when I moved; it must have been like January 2021. We have had a lot of change in the Directorate since then. The person who hired me and who was my boss left, and somebody else came in to be director, Jan Chodas, who in fact just retired [laughs], so I have a new boss. But they were all great. They have all been great. Then, Jan was planning to retire, and I suppose she and Laurie Leshin had figured out who was going to be her replacement, which is my current boss, who just started this week, Matt Wallace. But they were looking for a deputy because the deputy was retiring in March. Much to my surprise, Laurie called me for a meeting in her office and asked if I would consider doing it. I go, "Oh! Whoa! I wasn't expecting that at all." Because usually it was always an engineer in that position. There is a lot of what we call implementation supervision, of missions that are being built, and there are always problems. There hadn't been a scientist in that position before, ever [laughs], I don't think. I thought, "Oh, this is—unexpected." But I said, "Let me think about it for a few days." I then talked to the director for Planetary and my boss at the time, Jan Chodas, and I talked to the guy who was slated to become the new director after she retired, Matt Wallace. That's the first I had heard that Jan was retiring. I talked to Matt Wallace, who is our new director for Planetary. I thought, "It's going to be a big career change." But I'm in what would be called late career, and I don't feel that I need to lead another paper. I've got like 150 of them. [laughs] I can give back to the institution in another way. I made it clear that I still want to be involved in science, but I can be involved as a collaborator, as a coauthor, doing parts of work, giving my expertise, but this job is a new challenge. As I said, I like challenges, I like doing new things, and it's a very exciting position, and obviously a high-level position. The parking is better. JPL's biggest incentive for promotion is parking. [laughs]

ZIERLER: [laughs]

LOPES: It's something of a joke, but it's actually true. [laughs]

Brazilian Roots

ZIERLER: Let's go back to the beginning. I want to hear about your family background in Brazil. How many generations is your family in Brazil?

LOPES: Oh, dear. I suppose many generations. On my mother's side, one of the branches goes back to the first explorer sent by the king of Portugal, so that's kind of like 500 years. He went back to Portugal, but then he came back to Brazil. In fact, it's a really interesting story, because when he came to Brazil, he met and fell in love with the daughter of a native chief, and he married her, and actually took her back to Portugal. On her side, heaven knows how many generations. More recently on my mother's side, my great great grandfather was English, and I think some of that came through the generations. There was a strong English influence as well. Portugal and England have been aligned, were kind of allies, for a long time. On my father's side, I don't know as much about the family history, but it was more recent immigration, mostly Italian, Portuguese, and German. In fact, I'm not sure if it was German or Polish or Eastern European, because the surname is not quite German; I'm told it's more like Polish. There was that part as well. They were more recent. I guess the families on my father's side came in the late 1800s.

ZIERLER: What were your parents' professions?

LOPES: My mother, she had not quite a degree but you would say an associate degree in music. My father left school at 14 and was a businessman. My father came from a small town in the south of Brazil, largely Italian, German, some Portuguese family. His father died when he was ten, and he kind of left school—it was not unusual at the time—to work and help the family. My father was extremely smart. Actually his passion was architecture, and eventually, he—well, he was also a real adventurer, and he joined the Army—Brazilian males had to do service in the Army, and so he did that at 18 and ended up in Rio and never went back to the South. He worked in finance. He worked with construction firms, working with architects, even doing technical drawings. He just did a lot of things. He was very multitalented. He was an excellent cook. My school friends used to love coming to my house, and partly because they knew my father would cook. [laughs] When he left the Army, the national service, and ended up in Rio, his plan was to become a cook on a ship and see the world, but then he met my mother, and that ended there. He was very opportunistic, very multitalented, and adventurous, and I credit him a lot with my spirit of being adventurous, of exploration. When I, as a little girl, said, "I want to study astronomy," my mother was more like, "Can you get a job in that? How are you going to eat?" while my father was like, "Go for it!" In fact, my mother's father, my grandfather, was also pretty enthusiastic, because he thought that the only thing astronomers did was to discover comets, and he wanted me to discover a comet [laughs]. Which I haven't done, and funnily enough, my son did, when he was working at JPL as a summer student. He found a new comet with the NEOWISE data. [laughs] It has a NEOWISE name, not anybody's name, but he got his name on the paper. Anyway, there had never been a scientist in the family. My mother's mother was a school teacher, a pretty successful one, kind of well known.

It's interesting there had been these strong women in the family, because there was the Englishman, my great great grandfather, he only had one daughter, and his daughter became the first woman in Brazil to finish secondary education. She even had a book signed by the Emperor, at the time. Then she made sure to raise her kids to study. In fact, her husband died when the kids were still young, and she was in some financial difficulties, but rather than take the children out of school to help her, she said, "No. My children might starve to death, but they're not going to die ignorant." So she kept them all in school, and they all at least finished high school. My grandmother got a teaching qualification, and one of her sisters became one of Brazil's first trained nurses. She was selected by the U.S., by the Red Cross—that was after World War I—to come to the U.S. In fact, she studied here (nursing). I am not quite sure where. Then she went back to Brazil and eventually became director of the first nursing school in Brazil. So, there have been these strong women in the family who were well educated. I think that helped me. Because when I wanted to become an astronomer, and then I decided that I wanted to move to England to study there, it was kind of unheard of, that in my generation, parents, who were very protective of the girls, would actually allow a daughter to go to a foreign country. We wouldn't even normally be allowed to have our own apartments, to live by ourselves. You lived with your parents until you got married. But they let me go to England and study, and that was I think a big influence of my mother, coming from this family of strong women and really wanting me to be well educated, as much as possible. And my father, again, who even though he left school at 14, he not only wanted me to follow my dreams, but also was a big believer in education and academics. He told my sister and me, "I don't intend to leave you any inheritance, but while I'm alive, I'm going to pay for the best education that I possibly can." I think I really benefited from both those sides.

ZIERLER: Did you learn English growing up, or did you pick it up when you got to England?

LOPES: No, I couldn't have gone to England without speaking English. I started learning it, and that was largely my mother's influence, when I was like five. When I was six, I started going to an English private course for children. I learned to write and read in English and Portuguese at the same time. Then I was always in these private courses to learn English. Of course, you learn more and more. Then when I was 16, my parents sent me to England to spend a month at a school for foreign students. That perfected the language more, because there's nothing like being there. Still, when I went to college at the age of 18, it was still tough. I could understand it, but there were technical terms; there was writing. My writing of essays was very limited. I went to a very good college, University College London, but they were pretty tough [laughs], so I didn't have special allowances.

Astronomy and London

ZIERLER: How did you choose your course of study at London?

LOPES: As I said, my passion was astronomy, and that started with the Apollo program and the race to the Moon, astronauts. I wanted to be an astronaut, but then I realized I was female, Brazilian, and had terrible eyesight, so that was not going to work out. But I thought, "I can become a scientist." My aim in the future was to work for NASA. But I also had great affinity for England. At the time, going to university in England was a lot cheaper than the U.S. That all factored in. And, I had been to England before going to study there. I had been down to London a couple times. It was just easier. In the States, it's so big and there are so many universities, I wouldn't have really known where to go. What I did was I made contact with the British consul in Rio, and they gave me—it was all printed—brochures from universities, and I figured out that I could study astronomy in London, and Edinburgh, and there was one other place. It might have been Durham or Saint Andrews; I can't remember at the moment. I thought, "Okay, I know London. I've been to it. I love it. Up north there, Scotland, that's going to be too cold." So, I chose London. That was it!

ZIERLER: What were your considerations to stay in the program but to switch over to planetary science from astronomy?

LOPES: You have to realize that British universities are very different from those in the US; at least they were in those days, You signed up to do a degree in astronomy, you had a prescribed set of courses, and it was three years total. It was really hard, because it was absolutely rammed down your throat. You couldn't take fewer courses. You couldn't take French or dancing or [laughs] whatever. It was all, "This is what you're going to study." In the second year, most of the courses were prescribed, but there was a choice between two courses, and one of them was called Earth Resources, which was more on a geology, environmental science side. That turned out to be given by this professor called John Guest, who ended up being my PhD advisor. I really enjoyed that course. That's where I started getting more into geology. Then in my third year, you had more of a choice of courses, but I chose Planetary Geology because he was giving it, I was interested, and I thought he was a really good professor, really good lecturer. I really loved that course. Even though my final year project was in x-ray astronomy, and I had then worked during a summer for the solar x-ray astronomy people, I realized that planetary geology was what I really liked.

I went to talk to him, to ask if he would consider me as a graduate student. He didn't have funding for graduate students, but my parents agreed to pay. So, he accepted me. He was a volcanologist. He said, "Okay. I've never had a graduate student who was not a geologist, but you have a different perspective because you come more from like a physics background. So, there are projects you can do." But he also said, "You can't understand volcanoes on other planets unless you go to them on Earth." So, after the first academic year, that summer I went on two field trips—they were like three weeks long each—to just like help out with work on Mount Etna, where he did the bulk of his fieldwork. And, Mount Etna erupted, and I was totally hooked. I just thought that seeing a volcano in action was just the most exciting thing in the world. I really fell in love with that. Again, I didn't know anything about—not much at least—about geology, had never done fieldwork. Worse was that all the sports I had done, because of living close to the beach, had been related to the ocean—swimming and body surfing and all that kind of thing. Or, I used to have vacations on a farm, so it was like horse riding. But I hadn't done much hiking before, even. I had never done any camping or wilderness hiking or anything like that. He had to give me a list of what to buy, and it's like, "Hiking boots? Oh, where do I buy those?" [laughs] So I was really unprepared—had a lot to learn, again, some adapting to do. And I'll tell you, if you're not used to hiking, hiking over lava is really hard! [laughs]

ZIERLER: Tell me about developing your thesis topic.

LOPES: I did several projects in my thesis, but it was essentially comparing volcanoes on Mars and Earth. My first project was using Viking data from Mars. Olympus Mons, the largest volcano on Mars, has some material around it that's called the Olympus Mons aureole. It was totally mysterious. No one knew how it had been formed. He said, "Go look at the images, do some mapping, see what you can figure out." There is also a scarp around this volcano, and there have been some suggestions that the material and the scarp are somehow related. So, I developed this whole project about that, in fact, the volcano has actually very shallow slopes, was I think it shallower and larger in the past, and there was collapse, and landslides, essentially massive landslides, that formed this aureole material and left the scarp behind, and that had been triggered by volcanic activity melting permafrost. It became really quite a well-known piece of work, so I was lucky. There were also people who thought it was a crazy idea, but I didn't know any better [laughs]. At least it got referenced a lot. It got known. Then I did also a couple of other projects. One of them I carried on in my postdoc, it was essentially how lava flows move and develop, and how they change shape and thickness, and you can relate that to effusion rate, and even duration of eruption. That was much more terrestrial volcanology and modeling, but the aim was to apply it to lava flows on Mars, which I did. Part of that was during the postdoc. My (Ph.D.) advisor was the type who, he actually told me this, he said, "I'll point you in some directions, but if you can't figure out your own PhD project, then you shouldn't get a PhD. Because a PhD is all about independent research." Essentially, I see not every advisor, but some advisors in the U.S., giving their students a very prescribed PhD project, and it's like, "Here, student, this is what you are going to do." My advisor did not believe in that at all; it was like sink or swim. So I suppose I kind of got into this sink or swim mode [laughs] right from the very beginning, which would serve me well later on, I suppose, as I'm always thrown in at the deep end.

When I was getting close to finishing my PhD, the job situation in England was really bad. The guy who got his PhD just before me was applying for all kinds of postdoc grants and didn't get anything. He ended up going to Italy to do a postdoc there. I actually got a job while I was writing up the PhD, and it was in the Old Royal Observatory in Greenwich, part of the National Maritime Museum, and it was kind of in education and outreach largely. I also dealt with the collection of all the scientific instruments there, which was absolutely fascinating. I was there for three and a bit years. Actually, during that time, my head of department retired, my boss took a long maternity leave, so I ended up kind of like as the acting [laughs] head of a small department. That gave me management experience. I even went to some management courses back then. It was a very interesting job, and it also taught me how to talk to the press and do interviews. We had to do some of that. I think I became quite good at it. That again served me well at JPL, because they know I can do it, so I have done quite a bit of that. It eventually led to a lot of outreach and to the Sagan Medal from the American Astronomical Society. It kind of all connects, and all these things you do are useful experiences, if you know how to use them later in life.

ZIERLER: How did the opportunity at JPL come about?

LOPES: That was also interesting and a coincidence. As I said, I was writing up my PhD, and I was working full time. I used to come to where the University of London Observatory was, mostly in the evenings and weekends, to work on my thesis. I was there one evening, and my advisor had gone home, and the phone rang and I answered it. It was a guy, a researcher at JPL called Dave Pieri, who is now retired. Dave also did planetary volcanology and he wanted to talk to my advisor. But he and I had met at a conference—again, contacts are really important—so we remembered each other, we chatted a bit, and I said, "The situation here is really bad. I'm writing up my PhD, but there is no money for postdocs." He said, "Oh, NASA has this postdoctoral program and it's open to foreigners." I said, "Oh! Really! I didn't know about that." At that time, everything was in the mail; he mailed me the booklet with instructions on how I could apply. We were just starting email, and I mailed him, and I wrote a draft for a proposal, and there was a lot of mailing back and forth. I put that in, and I actually won it. That's how I came to JPL.

Now, the interesting thing is, I had a permanent position in England, because this position at the National Maritime Museum, Greenwich, was a civil service position. My former advisor by then thought that I was crazy to leave that and come to the U.S. for two years. Because that's all I had; it was one year, renewable for a second year, postdoc. In a way, it was kind of crazy. I had adapted very well to England. I had a house that I co-owned with a friend. I had friends. I had my support system. Job for life. [laughs] But I really felt coming to JPL was the right thing to do. It was what I wanted to do. It's like, "This is my dream." I wanted to work for NASA. I gave myself a little bit of a cushion by delaying starting the postdoc at JPL, and I got a six-month position in Italy, working with the other student I mentioned, Chris Kilburn, who had gone to Italy and in fact pretty much found a position there, it was like a series of postdocs and fellowships that were renewed, at the University of Naples. I had six months there in Naples, and I went there. We worked hard on a couple papers during that time. Then, I came to JPL. But before I came to JPL, I went to a conference in Arizona, which I paid for myself. I didn't have any funding to attend this conference. It was a conference on Mars. By chance, I sat next to a woman about my age who I didn't know. That was the session in which I gave my talk, and I stood up and gave my talk, and when I sat down, she turned to me and she said, "Oh, that was really good," and introduced herself. She was Adriana Ocampo, and she worked at JPL at that time. She worked with the Galileo NIMS team. She was from Argentina; I was from Brazil. We went to have lunch together. We struck a friendship there. When I came to JPL, she was the one who introduced me to people in the Galileo NIMS team and allowed me eventually, after the two years, to make that move from Mars and imaging data to Io and infrared. Again, these contacts are invaluable.

ZIERLER: Was there anybody when you started at JPL that you would consider a mentor, or did you even become a mentor to some of the junior people at that time?

LOPES: I would say that Adriana Ocampo was very definitely a mentor. Of course my advisor Dave Pieri was a mentor, but by then, he actually—it was weird, but he had moved from planetary to Earth science, and he was doing some different things. But he had a colleague who he had brought to JPL called Steve Baloga, who was working on planetary volcanology. Steve became something of a mentor as well. Then there was a woman volcanologist called Joy Crisp. They have all left by now, but she also became something of a mentor. Even—the person who first showed me around at JPL was a young woman who was working for Dave—she didn't even have a PhD at the time—was Lori Glaze, who is now head of Planetary at NASA. [laughs] She and I go back a long way. Even when I was looking for an apartment in my first couple of weeks, she said, "I'm going to go on travel. Why don't you stay at my apartment and look after my cats?" So I did that. In fact, I looked after her cats, later at my apartment, at least one other time. I have always been good at getting mentoring from a variety of people, and I think one should do that. Different people can help you in different ways. There are some mentors who are very much technical mentors. Other mentors are more like career development mentors. Others are more like, "I'll show you around, introduce you to people," help you make the contacts. I certainly have also mentored people in the past. I made friends quickly. I remember another guy who was an English guy who, I was a postdoc, he was a recent hire at JPL, and he even told me about the tax situation and that kind of thing. You just absorb information and advice from so many people. Making friends, being social, it really becomes important. During that time, while I was a postdoc, I also got married, so that was a different type of mentorship. I was still adapting to life in the U.S., which was quite different in many ways.

Joining the Galileo Mission

ZIERLER: Tell me about the Galileo mission at the time you joined. What were some of the big things that were happening then?

LOPES: Right before I joined, they found out that the high-gain antenna of the spacecraft didn't open. That was like—a near disaster. It's the main way of communicating, of downloading data, so everyone was like, "What are we going to do?" They had these tiger teams, they were trying to turn the spacecraft one way and another way, and did all this stuff to try to open the antenna, and it never opened. So, when I joined we had to replan – well, first we had an Earth flyby; I helped the planning for that, and with observation design. Then I started turning my attention to Jupiter and Io in particular. But we had to plan it a very different way. With most spacecraft you could get a lot of data. With Galileo we were going to have very little data. I compared it in one of my books to, in most missions, you're like a tourist with a point-and-shoot camera, digital camera. You take lots of images, you decide which ones are the most interesting, and a lot of the data only gets analyzed years later. With Galileo, we had to be like Ansel Adams. We had to put a lot of planning into, "I'm going to get that observation," and "What's that going to tell me?" in terms of a science experiment. The planning was a huge deal. I was learning. Again, I didn't know about spacecraft operations and designing observations and sequences. I didn't know the acronyms. That's always the biggest challenges in a new job at JPL; you have to learn all the acronyms [laughs]. I was again at the deep end. I remember a colleague who was also a science coordinator, and at first, in my first couple weeks, I was really like, "Oh, there is so much I don't understand." She said, "Oh, don't worry. For the first two months that I was here, the only question I got asked was, ‘Have you seen our team chief?' The team chief was Bill Smythe. It was always, "Have you seen Bill?" And I thought, "Funny enough, that's what I get asked."

ZIERLER: To clarify, by the time you joined Galileo, had you switched over to a hard money position?

LOPES: Yes, that was my first hard money position at JPL. When I was a postdoc, I helped with a few things, like an observation plan for the flyby, just to kind of like worm my way into the team, so they could get to know me, I could get to know them. There is a certain level of trust that is built when you help a team before you join them. Even though I was mostly doing my own research, I started going to their meetings, and I helped out. But that was my first position at JPL. I came in with a very low title. I wasn't even a science coordinator; I was a sequence integrator. But somehow soon that got changed to science coordinator. As I said, I never cared about titles. I just do the work. I think here, very much, people respect you for the work you do. They don't really care what title you have. I suppose some people might care, but most of us actually are looking at what you're producing.

ZIERLER: What aspects of both your graduate studies and postdoc were most useful? As you explained there was so much new for you to understand, to get up to speed on. What could you lean on, in terms of your scientific expertise for Galileo?

LOPES: I could lean on my general expertise in volcanology. And, I had been following Io research. Io was not in my PhD or postdoc research, but I was very interested in it. But, the general volcanology background helped. I think just the general experience of tackling different projects, it gives you a certain confidence. Also the ability to just dive in and just do it. [laughs]

ZIERLER: What were some of the big questions for volcanology with the Galileo mission?

LOPES: After Voyager, there was a really big question whether Io's volcanoes were erupting sulfur or silicates. That had been partially answered before Galileo, because there had been some observations actually from the ground, in the infrared, that had detected temperatures too high to be molten sulfur. But we didn't know if that was perhaps one volcano, so we didn't know if that was going to be the usual thing or not. The other question was we had only found a few volcanoes on Io, but there were a lot of volcanic features that you could see in the images. But what was active, what was not, composition, the style of activity—we can talk about that next time.

ZIERLER: Why don't we pick up for what happens with Io and all of your studies in volcanology there, and we'll take the story into the 1990s?

LOPES: Okay!

[End of Recording]

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, June 23rd, 2023. I am delighted to be back with Dr. Rosaly Lopes of JPL. Rosaly, it is great to be with you again. Thank you so much.

LOPES: Thank you!

ZIERLER: We ended last time talking about the discovery of volcanism on Io. I want to ask some general questions about the significance of this study. If we zoom out and we appreciate the history of space exploration, I wonder if you can explain, what was so significant about finding volcanism beyond Earth? What was so significant for JPL and for your career?

LOPES: I was not working at JPL when the Voyager spacecraft in 1979 detected active volcanism on Io. There were two things that were very significant. One is that we had seen volcanoes on Mars and Venus and possibly lava flows on Mercury—at the time it wasn't quite sure—and on the Moon, but we had never seen active volcanism beyond Earth. That was very significant. Second is that people were at first kind of scratching their heads, because Io is about the same size as the Earth's Moon, so the body should have cooled a long time ago, cooled enough that active volcanism would not be taking place today. But, coincidentally about two weeks before the Voyager flyby that detected active volcanism, a paper had been published in Science, and that was by Professor Stan Peale and two other colleagues, and they were analyzing the orbit of Io around Jupiter and the tidal forces that would be exerted on Io. Because Io is kind of caught in kind of a tug of war between Jupiter, which is very big, but it's further away from Io than the moons that are further out from Jupiter and Io, particularly Europa and Ganymede. These moons are all in resonance orbit. That is, for every orbit Europa makes, Io that's further in, makes two, and so on. What happens—the other moons, of course, are much smaller than Jupiter, but they are closer to Io. If these other moons weren't there, Io would always have a tidal budge facing Jupiter and there wouldn't be any active volcanism at all. But because these other moons are there, they kind of pull this tidal bulge towards them. That's what keeps the interior heated and molten, and that's why active volcanism happens. Since then, we have found that tidal forces are incredibly important in, for example, maintaining liquid oceans on icy moons and so on. Tidal heating is a really important process in the solar system. But at that time, other than this theoretical paper that actually mentioned the possibility that Io might have active volcanism, it wasn't something that people thought about. It's also interesting that there had been several hints, observations that hinted that Io had active volcanism, but people didn't believe it, because just the idea was so out there. When you look back at the history, it's like, "Wow, they should have put two and two together and figured it out." But it was considered a wild idea at the time, without a theoretical basis, and people thought, "Oh, well, the instrument might not be well calibrated," and so on.

ZIERLER: Moving into the 1990s, did you stay with the study of volcanism on Io? Was that a main course of your research at that point?

LOPES: Yes. I actually started studying Io when I came into the Galileo project, so that was in 1991. Before that, I had studied Mars and Earth, but not Io. But this opportunity came up, that the Galileo people had a position for someone in the near infrared mapping spectrometer team to do the plan for Io, lead the Io science. I was selected for it, so I started learning a lot about Io. Then when the data came back, I took the lead in analyzing the data and finding numerous hotspots, and analyzing hotspots and so on. I still study Io, a little bit, mostly by collaborating with other people. I have been working with the Juno team, actually, on their Io observations, and have been involved in three papers with them, as a coauthor. When the Galileo mission finished in the early 2000s and I joined Cassini, then I moved on to make Titan more the focus of my research, but I never stepped away from Io completely.

The Importance of Io

ZIERLER: In 1991, how well developed was the Galileo mission, when you joined?

LOPES: The mission was flying. The mission was launched in 1989. But soon after launch, they found out that the high-gain antenna had not opened. They had not made detailed plans for the observations yet. What happens is that we had to plan all that. We had to plan to make far fewer observations than expected. That means that each observation needed to be very well thought out, as a science experiment. You couldn't just have global coverage at high resolution or anything like that. That required a lot more planning.

ZIERLER: In what ways did Galileo build on the Voyager discoveries of volcanism on Io?

LOPES: We made Io one of the main focuses of the mission. Galileo studied Jupiter and its atmosphere, studied the magnetosphere, and studied the moons, but mostly the four Galilean satellites—Io, Europa, Ganymede, and Callisto. So, we knew there was active volcanism on Io. We knew there were about a dozen active volcanoes. I think I mentioned last time that just with the near infrared mapping spectrometer, and I was leading the observations and the analysis, we found 71 active volcanoes that had not been found by Voyager or ground-based observations that were at the time beginning to be higher resolution.

ZIERLER: I wonder if you can explain some of the technical improvements that allowed Galileo to discover so many more volcanoes than what Voyager was able to see.

LOPES: We had a near infrared mapping spectrometer, which Voyager did not have. Also we had repeated observations. Because the two Voyager spacecraft flew by Jupiter, but then they went on to the outer solar system, the time they had to observe was much more limited. Galileo was in orbit around Jupiter, so we could observe Io from mostly far away but we still had enough resolution to detect the really bright volcanoes. The near infrared mapping spectrometer was designed mostly as a compositional experiment, but it was really good at detecting heat. That's how we found so many hotspots.

ZIERLER: Is the discovery simply more volcanoes, or did you more about how volcanoes operate on Io?

LOPES: We learned a lot more about how volcanoes operate. The "more volcanoes" is good, but what's important there is that it's a much more active body than we realized. The distribution of the volcanoes, we're still working on that with more recent data, but it can tell you something about the interior of the body. I can't say that we have clear answers yet, but depending on some assumptions, it can tell you how the heat is dissipated in the interior, and where the heat is dissipated, if it's in the deep interior or if it's closer to the surface. The patterns that are predicted of the distribution of hotspots and heat are different for different interior models. With Galileo, we did not really get much data at high latitudes, and the latitudinal distribution is really the discriminator there, so we're now filling that in with Juno. With Voyager there was still some doubt whether the volcanoes were silicate, like those on Earth, or if they were sulfur, because Io has a lot of sulfur dioxide on the surface, but with the infrared NIMS, the instrument, we were able to show definitely that at least the vast majority of volcanoes we looked at had to be silicate, because sulfur melts at lower temperatures. The temperatures were too high to be sulfur. There are one or two volcanoes that we still think might be possibly sulfur volcanoes, but the problem is that because lavas cool very quickly, if you detect a temperature of like 300 Kelvin, you don't know if that's sulfur or if it's silicates that have cooled down. Similarly we detected some very high temperatures that were too high to be ordinary basalt, and there is still a debate whether those are what we call ultramafic, which are primitive lavas similar to the lavas on Earth that erupted mostly billions of years ago, or if they are basaltic lavas that have kind of been superheated on ascent. We really need more data to sort this out, but it raised the possibility that Io's lavas might be similar to the very primitive lavas on Earth, and that got us very excited, because on Earth, you can no longer see those lavas as active.

ZIERLER: Were you exclusively focused on Io, or as part of Galileo you were looking at the other satellites as well?

LOPES: I was really focused on Io. I was interested in what was going on with the other satellites, but I really focused my research on Io.

ZIERLER: Is there evidence of volcanism beyond Io in our solar system?

LOPES: Yes. Recently there was a result that showed that there was a change on the surface of Venus during the time that Magellan was observing, which was in the early 1990s. Again it was suspected that Venus could have active volcanism, but it was only recently that someone looked very carefully and deeply into the radar data and was able to say that, yes, there was a change here, which the most likely explanation for is that volcanic activity happened during that time. We know that there was silicate volcanism on the Earth's Moon, on Mercury, and Venus in the past, probably still active on Venus even if not very frequently. And then Mars, there are a lot of big volcanoes. Then, Io, active volcanism. Then moons, the icy moons, we found with Cassini active plumes on Enceladus. But those plumes come from what we call cryovolcanism, which I may have talked about before, there is water under an ice crust. Then if it reaches the surface, that's cryovolcanism. It's happening on Enceladus and may still be happening on Europa and many other moons of the solar system,

ZIERLER: I was asking about evidence of volcanism beyond Io in the solar system.

LOPES: I think you recorded when I talked about Venus and Mercury. We have had volcanism in the past in many other bodies. On Venus, recently, people have found evidence of a major surface change, in the Magellan data, from the early 1990s timeframe. We think volcanism is still happening on Venus, maybe not all the time but still happening. Then we have cryovolcanism in the outer solar system. That's icy moons that have an ice crust and oceans of liquid water under the icy crust. Cassini found active volcanism on Enceladus. Voyager found active cryovolcanism on Triton, which is a moon of Neptune, although people have proposed an alternative explanation for the Triton Voyager data. Anyway, it's likely that cryovolcanism is going on or has gone on, on many of the icy moons of the solar system that are large enough. On Titan, we found features that are consistent with cryovolcanoes. There is some debate, but maybe Titan had cryovolcanism in the past. So, volcanism is a really important process in the solar system.

ZIERLER: Going back to a question from our previous conversation, with all of this new discovery of volcanism beyond Earth, did you take it as an opportunity to understand volcanism as a two-way street, to understand what's happening beyond Earth to better understand volcanism on Earth?

LOPES: Yes, we learn a lot from comparisons. You're always comparing data from different bodies, because the conditions are different. Certain parameters are different. Of course gravity is different. What controls volcanism on Earth is plate tectonics. None of the other planets have evidence of plate tectonics. If we only looked at the Earth, we would expect if we found active volcanism, we would find plate tectonics, and that's not at all the case. We also found that tidal heating is a major factor in driving volcanism. You can go a lot more detailed into, for example, modeling of magma ascent and lava flows and find out more from those comparisons. It's always a two-way street.

Titan and the Cassini Mission

ZIERLER: Tell me about joining the Cassini mission in 2002.

LOPES: I was looking for another mission beyond Galileo. I didn't know which; maybe a possibility was to go back to Mars. There were, by then, several Mars missions in the works. Actually, Pathfinder had gone. Spirit and Opportunity I think were launched. Anyway, at that time, I was looking for another mission. By then, there were a lot of people working on Mars, and I was more attracted towards the outer solar system. I talked to a colleague of mine who I had worked with on Galileo, on the NIMS team, Larry Soderblom, very famous planetary geologist. He said, "Oh, you should join the Cassini radar team. They need help." I said, "Well, but I don't know anything about radar." He said, "Oh, don't worry, you'll learn." I then found out that the person who had the position of investigation scientist for the Cassini radar at JPL wanted to retire. I talked to the team chief and talked to the guy who wanted to retire, called Ladislav Roth, a wonderful guy from Slovakia, and they thought, "Yes, you're obviously a good scientist, so let's talk." I started talking with them and learning about what they were hoping to do. We hadn't gotten to Saturn yet. I got very interested. I got the position, and then started working particularly on Titan, which was going to be the main focus of the Cassini radar. That has been wonderful. I'm still working on [laughs] some of that Titan data, too!

ZIERLER: Why Titan? What was so interesting to you about Titan that that became such a longstanding research focus?

LOPES: Titan is a very large moon—it is about the size of the planet Mercury—and very mysterious, because it has a very dense atmosphere. So, when Voyager flew by Titan, all it saw was like this orange ball. It just saw the atmosphere; it couldn't see the surface. The radar was put on Cassini because synthetic aperture radar can get images of the surface, can go through cloud and haze. At the time, Titan's surface was the largest piece of real estate in the solar system that we had not imaged at all, so it was very exciting to find out what was happening beneath the clouds. I thought there might be volcanoes. Really there could be all kinds of things. We knew it had exotic composition, hydrocarbons, and seas of hydrocarbons had been postulated, which we found. It really was an exciting, mysterious world. And, it did not disappoint. The geology is wonderful. It's in many ways similar to Earth's. We have interaction between the atmosphere and the surface, so we have wind, we have rain, we have dunes, we have erosion. It's very varied geology. It has turned out to be great.

ZIERLER: I wonder if you can explain the technological developments that allowed Cassini to peer beyond the cloud. How is that possible?

LOPES: Actually, synthetic aperture radar had been used for quite a long time on Earth. In fact it was used on Venus for Magellan. That's how Magellan was able to image the surface of Venus.

ZIERLER: You said that synthetic aperture radar had been used long before Titan. Were the technological developments better? Were you able to do better imaging because of advances in the technology? Or it just sort of is what it is, and it was being applied to Titan?

LOPES: I'm not actually sure about the answer to that question, because I'm not a radar technical expert. The technique had certainly been around. People were of course careful with what wavelength they chose, because you can have a variety of radars depending on what you are trying to do. There are sounding radars if you're really trying to see beneath the surface, but for this one, we were trying to see the surface. Then it had several modes. It had also an altimetry mode that we could get precise topography, but only in short chunks. So, there were certainly some innovations. Then, for the data analysis, as well. We had a fantastic team. In fact, Larry Soderblom, who suggested that I be on this team, he was on the Cassini radar team as well. We had some really good people. Then I started getting postdocs and they joined the team and they worked on the data. It really was a fantastic time. The Cassini radar team was a really nice team to work with.

ZIERLER: I wonder if your close study of Titan got you more involved in the question of habitability and even astrobiology.

LOPES: Oh, yes, much more. Because one of the really interesting things about Titan, is that it's got so much organic material, and you wonder if it could be habitable. With Cassini, we confirmed that there was a liquid water ocean, global ocean, under the ice crust. The question is, can this ocean be habitable? The surface of Titan is very, very cold, so it's not very good for life as we know it. It has no oxygen. The water at the surface is ice, so the most likely place for life is really the ocean under the ice crust. First I was studying the geology, which I've carried on, and I'm still studying, collaborating with people. I published, for example, the first geological map of Titan. Now, we are doing work beyond that, led by a colleague of mine at Arizona State University, to make a USGS geologic map of Titan, and that's an archival product. I published it as a paper, but if the USGS publishes it, it's a real archival product, for the ages. But then there was always, yes, this question of life. Some colleagues suggested that I lead a proposal to the NASA Astrobiology Institute, called the NAI. This was like six years ago. They had a proposal call every two or three years, and you could propose big research projects, with five-year projects, with quite a bit of money for a large team to investigate a really important astrobiological question. Some colleagues of mine suggested that I should lead one of these proposals on Titan. I said to them, "I never worked on astrobiology." They said, "Well, but you know about Titan." So I got together with some astrobiologists and geophysicists and chemists, and we wrote this proposal, which was to figure out if material, organic material, from the atmosphere and surface of Titan could get down to the ocean, and if the ocean would be habitable. Could certain bacteria, for example, that we know on Earth, could they survive Titan conditions? High pressures, low temperatures. Then could cryovolcanism bring those things from the ocean to the surface? If it's 100 kilometers under the surface, then you have no way of getting at it, but cryovolcanism can bring it up.

We have people studying the atmospheric chemistry, people studying how material, the organic material, moves around the surface. Then, something that we had not put in the proposal, and it was actually our biggest sticking point, was how would material get from the surface through the ice crust into the ocean. Then, by sheer luck, I'm from Brazil, and a Brazilian professor contacted me that he wanted to do a sabbatical at JPL, and he's an expert on impact craters. As I was figuring out a project—because he is an expert on impact craters on Earth, and I was trying to figure out a planetary project—I said, "Can we do modeling to find out if an impact on Titan that produced a big crater, could it get through the ice crust and bring material from the ocean to the surface and get material from the surface to the ocean?" We worked on that, and it was a very successful project. He brought in another colleague to help out with the modeling. In fact we found that for at least the largest impact crater on Titan that we know of, under reasonable assumptions, let's say, of the thickness of the ice and so on—yes, you could get that surface-ocean exchange. And maybe with some of the smaller craters. There are other colleagues doing work on that now. Again, you might be able to get at least some sort of melting of part of the ice crust and maybe some material going down to the ocean. All that eventually also led to a workshop in Switzerland, where several of us, some from my team, but people from other places, got together, and what we are trying to figure out is, if you can get enough material, organic material, into the ocean, to serve as, quote, "food" for the organisms that might be there. It's a very big question, and I don't claim that we have the answer yet, but we got some interesting results, for example working with biologists from the University of Illinois Chicago, and they made like a pressure chamber that reproduces Titan conditions, and they are finding that there are bacteria that can survive in those conditions, and even reproduce. They are trying to figure out how these organisms, these bacteria, kind of change their DNA, or adapt to those conditions. It's something I didn't know, but if you put some organisms under increasing pressures, you kill some, but then some survive and they can adapt. It's very interesting. I like to call it the Titan torture chamber. They don't like that very much. [laughs] It turned out to be a great project, great team, and many results still to come out.

ZIERLER: I wonder in what ways you see the mapping of Titan as laying the groundwork for a future mission where we might actually put a rover or a submersible beneath the ocean on Titan.

LOPES: Actually some of my colleagues proposed a mission that's a drone on Titan, and the drone is going to land on several places on Titan and make some measurements of the chemistry of the surface, to look for—life, or at least habitability, conditions suitable for life. The work we have done, not only the mapping but—that informed about what are, for example, safer places to land. They are going to land between dunes, near a crater. Because there might have been that interchange between surface and ocean, a crater is a good place to make measurements. Our mapping is not at a very fine scale, because we don't have high resolution data, but I think it certainly informed different terrains to go to, for example.

ZIERLER: Based on what you have seen so far, do you think Titan is most promising for finding extant life beyond Earth in our solar system?

LOPES: I would say that is somewhere that should be investigated. I think there are more promising places, particularly Mars, Enceladus, and Europa. Because on Titan, we know it's an ocean world, and there may be life in the ocean, but in terms of looking for life, cryovolcanism—it's not happening at the moment. On Enceladus, there is material coming up from the ocean via plumes. There is still a little bit of debate whether those plumes that are like geysers are coming directly from the ocean, or maybe from pockets in the ice, but there is a good possibility that ocean material may be coming directly to the surface as plumes. If you sample the plume, you're likely directly sampling material from the ocean. So, Enceladus is a very good place to look for life. Mars, we're bringing back samples. There may have been life on Mars. We know it had water. We'll find out a lot from Mars Sample Return.

Adopting Administrative Responsibilities

ZIERLER: Back on planet Earth, when did you start to take on an increasing leadership, administrative role at JPL?

LOPES: It was I think around the time or shortly after I joined Cassini. I would have to look at my resume, but I became what is called a group supervisor. I was supervising the people who worked in planetary geology. I did that for several years, and that was like a one day a week job. It allowed me still to work on Cassini and do a lot of research. Then I became a deputy section manager for like a year and a half. That was an increased load. Then I became a section manager, and while I was a section manager, I led and won this NAI Titan proposal. It was tough, because it was over half time as Section manager; it was more of a three to four days a week job. I had a postdoc, I was doing my own work but also contributing to other people's. Then I became in early 2021 the directorate chief scientist for Planetary Science. Again, that was like a half-time position. I gave up section management before that and then moved to the position of directorate scientist half time. I was working on Titan the other half of the time. Now I'm in what is almost a full-time position in the Directorate. I don't have so much time to do my own research anymore, but I feel that at this stage of my career, what is really valuable is that I guide other people and I work with them. I don't need to lead my own papers. I can contribute to people's papers. I can have postdocs, work with students, which is what I'm doing, work with early career people and help them out.

ZIERLER: Given that there is still data on Titan to be understood, to be reviewed, just how much data is there, and what remains to be known? What can we continue to learn about Titan as the data continues to get analyzed?

LOPES: It kind of never ends. Even though we look forward to the next mission to Titan —that is Dragonfly—some of it is just analyzing data with better techniques, be it better software, image processing, A lot of it is experimental. You're doing experiments using Titan conditions, to interpret the data better. We can still get new data, some colleagues of mine, for example, are using the ALMA submillimeter telescopes to continue to look at Titan's atmosphere, and detecting new organic molecules. It kind of all comes together.

ZIERLER: Bringing our conversation closer to the present, tell me about how the JUICE mission, the Jupiter Icy Moons Explorer Mission, how did that get started and what has it been like collaborating with the Europeans, with ESA?

LOPES: How it got started—there were some studies that NASA did about missions to Jupiter and satellites, and actually also Saturn and satellites. I was on several Titan studies. There was this idea that got studied that it was for NASA to do a mission to Europa, and the Europeans to do a mission to Ganymede. Those eventually got realized as Europa Clipper, which we are planning to launch next year, as a JPL mission, and JUICE, which launched this year. There are three NASA instruments on JUICE, including a JPL radar that colleagues of mine are working on. I actually am a co-investigator on the camera on JUICE. Unfortunately, NASA restricted the NASA funding to the U.S. instruments, so the co-I's on European instruments didn't get any funding. We call ourselves the orphan co-I's. But we can collaborate in a small way. I have given advice on planning the camera observations of Io. But it's mainly European and other colleagues who are leading it.

JUICE and Circling Back to Io

ZIERLER: In some ways, this is a very full circle for you in your career, going back to Io. What do you hope to learn? After all of your study, what more is there to understand about Io, and what might JUICE to do get you there?

LOPES: JUICE, I have to say, is not going to get very close to Io, so I don't expect that there would be like earth-shattering results about Io coming from JUICE. Its mission is really about Ganymede. But Io is always changing. There is volcanism. There are new volcanoes, new plumes. There is always something going on. So it's part of putting all the pieces together to make a full picture. At the moment, I'm collaborating with the Juno team. Juno is a NASA mission managed by JPL. It is in orbit around Jupiter. The mission was designed to study Jupiter. It has an infrared instrument that is Italian. But this infrared instrument started looking at Io, so I have been collaborating with the Italians, coauthored some papers with them. Now, at the end of its mission, Juno is getting closer flybys of Io and in December is going to do a really close flyby. Juno has a very different orbit from Galileo. While Galileo was equatorial, Juno is observing the high latitudes very well, which is what we could not get with Galileo, and we cannot get from ground-based data, in terms of the distribution of hotspots, how intense those volcanoes are. I mentioned before that distribution of heat with latitude gives you clues about the interior and what's happening with the dissipation of the tidal heating in the interior. It's putting more pieces of the puzzle together, and it has been very exciting.

ZIERLER: Now that we have worked right up to the present, with your current work, the things that are happening in space exploration, for the last part of our talk I'd like to ask some retrospective questions about your career, and then we'll end looking to the future. One overall question that you might be uniquely suited to answer—of course in the past two decades, JPL has become much more involved, become much more of a leader, in Earth science. Do you see your dual expertise in volcanology and geology on the Earth and beyond the Earth as contributing to JPL's increasing leadership in Earth science?

LOPES: I have been very focused on planetary, so I have not really worked with the Earth Science Directorate at JPL. I think that having this background in Earth science helps me having a broader understanding. A big part of JPL's Earth science is climate, and I don't have expertise on that. But since, for example, for internal investments, we all comment on each other's proposals, I feel yes, it helps me, that I have some background in Earth science, also astrophysics, because my first degree is in astronomy. It's good to have that broad background to understand better what my colleagues in the other directorates are trying to do.

ZIERLER: You're so involved with scientific societies and academic publishing and service work in planetary science in general. What are the academic or scientific societies that are most important to you, or the ones that you feel are really deserving of your interests and resources?

LOPES: There are many. [laughs] I have a bad habit of not liking to say no, so I have ended up doing a lot of service work. I would say one that I really, really like its mission is COSPAR. That's an international organization that is for cooperation in space research. COSPAR started out as a forum where the American and Russian scientists could talk to one another during the Cold War, but it's still an international forum where people from many different countries can talk together and collaborations are made. Even mission collaborations sometimes come out of that. Now we're seeing a lot of countries having space agencies, geting into the space program, and I think that's very important. I think that space is something that really unites people. When you look at the Earth from space, you don't see any borders. And everyone loves space. [laughs] I have a role in one of the COSPAR what they call the subcommissions, in Planetary, and I'm the Vice Chair. I helped to organize a COSPAR meeting in Pasadena some years ago. I think that's really important to me.

There are others. The Division for Planetary Sciences of the American Astronomical Society, that's smaller in scope, but I have lots of friends there. They have much smaller meetings, but that's very nice as well. The American Geophysical Union is one that has everything, so their meetings have like 20,000 people, but that's good, because when I go there, I can go to the volcanology sessions, for example. It's not all planetary; there is a wide variety. Also, I'm on the International Academy of Astronautics, which is a smaller organization but very international. On the whole, I like international organizations, because I think it's really important for us to work together with other countries, particularly now that we have so many collaborations —of course, we have Europe, we have Japan, we have India. Even the United Arab Emirates has a mission to Mars, and South Korea, a mission to the Moon. There are really a lot of opportunities for collaboration in space.

ZIERLER: You have been honored in so many different ways with awards and recognition for your research, far too many for us to cover here. But I wonder if there are any that you might single out, either internal to NASA and JPL or external among scientific societies, that have either been truly personally meaningful to you, or have given you a platform where you can really communicate the science beyond your immediate scholarly circles?

LOPES: Yes, I have been very fortunate that my colleagues have honored me in different ways. One that's particularly meaningful is the Carl Sagan Medal from the Division of Planetary Sciences of the American Astronomical Society. I got that in 2005. That is given to a planetary scientist who excels at communicating science to the public and inspiring the future generation. That's very meaningful, because I think that each of us, scientists here on Earth, we can do good work, but we can do a limited amount of work, and inspiring future generations is the most important thing we can do. Also inspiring the public. The public funds what we do, and that's really important that we communicate how incredible space science is. I have a lot of, let's say, followers in Brazil, and I often talk to students there. I think my story is inspiring because when I grew up, there were no scientists in my family. The idea that this little girl could become a scientist and work for NASA is inspiring to them.

ZIERLER: At this point in your career, in your capacity as a mentor, what are some of the real points of satisfaction in being a mentor to younger scientists, in the way that you were mentored earlier in your career?

LOPES: Every success of someone you mentored is a thrill. For example, when they publish a paper. Now a student I have collaborated with for a long time just got her PhD and in fact is coming to JPL as a postdoc. A postdoc of mine is very close to publishing what I think is a really important paper. You get really thrilled by every success, of everyone. I had at JPL a postdoc originally from Greece, and she went back to Greece and now is the chief scientist for the newly formed space agency in Greece. Yes, everyone you mentor, to see them become successful, it's a really big thrill. In a way your students and postdocs and all the young people you help are a little bit like your kids. [laughs]

ZIERLER: Finally, Rosaly, looking to the future, what is left for you to accomplish personally, and what are your remaining greatest curiosities about the solar system that you hope to be around for, to be active, to take part in the discovery?

LOPES: That's a tough one. I am interested in a lot of things. I'm really curious to see the results from Dragonfly. That's the mission that is going back to Titan as a drone. I'm not directly involved in the mission, but several of my friends and collaborators are. I'm very curious about what Juno is still going to find at Io, and then JUICE. I want to see missions launched like Europa Clipper, and successfully getting there, getting great data. But, I'll be just as happy doing research on another body. Now that I'm getting older, I'm thinking maybe I shouldn't focus so much on the outer solar system because it takes a long time to get there. Maybe it should be more the Moon, for example. It's really quick to get there. [laughs] But I'm curious about a lot of things. I see my role now much more as helping JPL as an institution, mentoring other people. I am really enjoying this job I have now as Deputy Director for Planetary Science. It's a different perspective, but it's something that I am really enjoying. I'm probably one of those people who, in some way or the other, I'm going to work until I die. [laughs]

ZIERLER: You don't know how to retire?

LOPES: Well, I might retire, but it doesn't mean that I'll stop working. And, who knows what the future holds. I'm still very excited about the future. I'm not ready to go lie on the beach yet. Maybe I'll never be ready to do that! [laughs] Maybe I'm always going to be involved in something, or writing a book, or whatever it is. Also, doing a lot of outreach. I really enjoy that. I had a friend who was a true explorer and had had many adventures. Someone asked him what had been his greatest adventure. And he said, "I hope I haven't had it yet." [laughs]

ZIERLER: [laughs]

LOPES: That's really my philosophy. I don't know what the future holds, but I hope that I haven't achieved my best yet. Trying to do more.

ZIERLER: On that note, this has been a wonderful pair of conversations. I'm so glad we were able to do this and capture your perspective. I'd like to thank you so much.

LOPES: Oh, thank you.

[END]