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Linda Spilker is the Cassini Project Scientist at the Jet Propulsion Laboratory in Pasadena, California.
She has been with JPL since 1977—thirty of those years with Cassini, NASA’s robotic probe to the Saturn system. She received her PhD (summa cum laude) in geophysics and space physics from UCLA in 1992.
I spoke to Dr. Spilker about her childhood fascination with space, her work on the Voyager mission, and the possibility of life on the Saturn moons Enceladus and Titan. Here are excerpts from our conversation.
Bill Retherford: Your interest in space began early.
Linda Spilker: I grew up during the time of the Mercury, Gemini, and Apollo missions. I have vivid memories of the first moon landing. I was sitting with my dad on the couch, watching Walter Cronkite on TV, and that grainy image of Neil Armstrong as he slowly went down those steps. The first time a human being had set foot on the moon. It was just incredible. There was a sense this was history in the making, and a tremendous sense of pride that the United States was leading the way. It gives me goosebumps even today.
I also remember thinking, “Won’t it be great when they start to send scientists to the moon too?” Because I had a dream from a young age of being an astronaut/astronomer. I had a tiny little telescope when I was in third grade, and looked at Jupiter and its moons, and looked at Saturn. I was particularly interested in Saturn. It had these incredible rings that you could actually see, even with a tiny telescope. And I thought, “If they ever built a telescope on the far side of the moon, then I could be an astronaut and go use the telescope to look even further into space.” I really loved science, I really loved math.
BR: At the time, women were often discouraged from pursuing careers in math, science, and engineering. Did that ever happen to you?
LS: When I was in high school, I remember telling one of my counselors I was thinking about majoring in math in college. I remember this person saying, “Well, you know, that’s not something that women often do. Have you thought about being a nurse or a teacher?”
BR: Did your parents encourage you?
LS: I had a tremendous amount of parental encouragement. My mom loved math too. She was the only girl in her algebra class, and felt a lot of peer pressure not to take it. She didn’t take any more math beyond algebra. I think she always regretted that. I was the oldest of four girls, and she told each and every one of us, “You are good at math.” And we believed her. My parents always said, “Do what you love, take the classes that you’re really good at, that you really like, and go for it.”
BR: When did you start at the Jet Propulsion Laboratory?
LS: I began working there in 1977. I was only 21 years old. It was my very first job right out of college. They said, “Do you want to work on this mission called Voyager?” I said, “Where is Voyager going?” And they said, “Jupiter and Saturn, and if all goes well, on to Uranus and Neptune.” And I said, “Sign me up.” Little did I know that only a few months later, there I would be, down at the Cape, watching one of the Voyager launches. And I thought, “What a great way to launch my career.”
BR: The field was largely male-dominated then. But were there other women at JPL?
LS: There were two other women working on Voyager when I started. They were very close in age to me, and we immediately became good friends. We even had our children around the same time. There was a five-year window on Voyager, between the fly-by of Saturn, and the fly-by of Uranus—and we decided to start our families in that window. That was a wonderful thing to share with these other women. We were Voyager Moms. Our children knew each other and played together. I tell my daughters their births are based on the alignment of the planets.
BR: Voyager 1 flew by Saturn in 1980. What are some of the things you remember?
LS: The rings. I fell in love with Saturn’s rings. They weren’t just bland sheets of material separated by gaps. Instead, it was this intricate incredible structure looking like grooves on a phonograph record. I was completely amazed because it was so different from what we expected.
One of Voyager’s jobs at Saturn was to get a really close look at Titan, a fascinating moon with a thick atmosphere and chemistry much like the early Earth. But when Voyager flew by, we found a haze-enshrouded world. We couldn’t see through to the surface. Right after that fly-by, a group of scientists got together and said, “We need to go back.” So they started talking with NASA, talking with the European Space Agency, and began to plan what became Cassini.
As Voyager wound down in 1988, I was asked to work on a study for a mission to go back to Saturn. It didn’t have a name yet. But it would take what we had learned from Voyager, formulate the science questions that were left after the Voyager fly-bys, decide what instruments we might need to answer those questions, and put together a proposal for NASA. When they asked me I said, “Of course! You’re going back to Saturn. I want to be a part of that.”
BR: What a nifty segue. Captivated by Saturn as a child, then discovering its secrets with Voyager and Cassini.
LS: I feel like I was in the right place at the right time with the right education. I’ve now worked on Cassini for one Saturn year. So many things happened in those thirty years. Those decades have flown by. Cassini has revolutionized our understanding of the Saturn system—from the planet itself, to the rings, to the icy moons, including Enceladus and Titan. Probably the key discoveries from Cassini have to do with those two moons.
BR: What are some of them?
LS: Enceladus is a tiny world, only about 300 miles across. From Voyager, we knew Enceladus was bright white and icy, with what looked like a fresh young surface. But the south pole was in darkness, so we missed four large fractures. We’ve nicknamed these fractures “tiger stripes.” And coming out of the tiger stripes are the geysers, jets of material, water vapor and water ice particles, shooting into space. The jets were going off every single day whenever Cassini looked. We flew closer and actually sampled and tasted the gas and the particles. We found out the water was salty, there were organics, there was carbon dioxide—all this incredible information about the ocean coming out to Cassini.
Unfortunately Cassini didn’t carry any instruments to look for life. That will remain for a future mission to come back with the instruments to do the experiments to answer the question: Could there be life in the ocean of Enceladus?
BR: How likely is it that life is there?
LS: The conditions are right. The question is, what’s that spark, what does it take to get life started? The first place where life usually starts is with very small microbes. Perhaps there are microbes even now coming out of the jets and going into space. If we go back, and find evidence of life coming from the geysers, then it tells us maybe it’s not so hard to get life started. Or if there’s no life there, maybe there’s something else you need to get it started. Either answer would be profound.
If we find life on Enceladus, if these ocean worlds support life, then the opportunities for life on other planets on other stars just go up tremendously.
BR: What about the possibility of life on Titan?
LS: Titan has liquid lakes and seas of methane. It’s a remarkable world. Methane plays the role on Titan that water plays on the Earth. You have methane clouds. Methane rain. Methane flows through river channels and fills the lakes and seas. There could be a very interesting kind of life that might thrive in a liquid methane sea. It would be very different from life here on Earth. It might just be tiny little microbes. We haven’t seen any indication of any advanced life forms, but it’s an intriguing possibility.
BR: What was the end of the mission like?
LS: When Cassini plunged into the atmosphere of Saturn, it really was a bittersweet moment. Cassini had done everything we asked of her right till the very final second. There was a very gratifying sense of accomplishment. At the same time I realized this Cassini family had been together for almost three decades—and now the members of the family would go their separate ways.
Imagine, three decades, living with all the families in your neighborhood, and now you see everyone packing their boxes and moving out. And so there was that sense of sadness. The breakup of the Cassini family.
BR: But Cassini left quite a legacy. And a lot of data.
LS: We've had data coming back for thirteen years. The Cassini scientists have really only skimmed the cream off it. There will probably be decades of analysis. Who knows what will be found, looking at those different bits of data? Who knows what fascinating discoveries are still out there?
