"As Cassini ends, part of me is saying, 'I need to go back,'" Linda Spilker says.
Wielding a fresh Bachelor's degree in physics, a 22-year-old woman walked into NASA's Jet Propulsion Laboratory in 1977 and interviewed for a job.
Staff at the lab looked over her resume and offered the young woman a choice. Would she like to join an existing mission at Mars, called Viking — or a brand-new mission called Voyager?
"Well, where is Voyager going?" the woman asked. Jupiter, Saturn, and possibly onto Uranus and Neptune, a staff member said.
She remembered peering at Saturn through a tiny telescope in third grade. Intrigued by the world, she made her choice.
Saturn would guide Linda Spilker, now 62, to be many things over the next 40 years — planetary scientist, imaging expert, author of dozens of scientific studies, recipient of more than 20 professional awards. She'd also become one of many "Voyager moms" who synced the birth of her kids to a rare planetary alignment.
Her efforts helped find a warm, salty ocean hiding beneath the icy crust of Saturn's moon Enceladus, something she's described as "one of the most astonishing discoveries" in space exploration.
"I feel remarkably lucky. Right place, right time, right education," she said. "I wouldn't trade it for anything."
In a wide-ranging interview with Business Insider, Spilker reflected on the history of Voyager and Cassini, battling sexism, balancing work and family life, and pushing to answer humanity's most evocative question: Are we alone?
Spilker's path to Saturn — and her first full-time job as a Voyager team member — began to take shape in school, though not without a struggle.
"Growing up and taking a lot of math and science as a woman, sometimes that was kind of challenging," she said.
Spilker recounted an especially discouraging conversation with a male high school advisor.
"I said, 'I want to major in math or science in college,' and he said, 'Well, you know, those aren't really careers for women.'" He instead recommended becoming a nurse or teacher.
But Spilker's mother encouraged her daughter to ignore this sexism and chase her dreams.
"[Mom] ran into the same thing — she was the only girl in her math class — and then felt like she couldn't really continue because of the peer pressure," Spilker said. "And so all four of her daughters heard how women are great at math and science: 'It's wonderful, you go for it, do it,' and so we all took that to heart."
She later added: "I made sure my daughters heard the same story." (Both went on to study math and science and pursue technical careers.)
Years later on the Voyager team, Spilker leveraged her physics background to work on the spacecraft's infrared spectrometer, called IRIS: an all-in-one thermometer, molecule identifier, and light detector.
It was the perfect device to study Saturn's gossamer-thin rings. So Spilker not only wrote her PhD thesis on them, but also became one of the world's foremost experts on the icy structures.
NASA launched Voyager 1 and Voyager 2 in 1977 — the same year that Spilker joined the team — and she said the work swung between leisurely and unrelenting.
The twin probes took more than a year to reach Jupiter, for example, but researchers sprung into action as their days-long flybys approached.
"It was bursts of activity. You're super busy for a few months around a flyby, but then it kind of dropped off until the next flyby," Spilker said.
Voyager 1 reached Saturn in November 1980, documenting the planet and six of its moons before it sped toward nothing in particular and left the solar system in 2012.
Voyager 2, meanwhile, reached Saturn in 1981.
Because of Voyager 1's success at Saturn, however, NASA reprogrammed the probe to take advantage of a rare planetary alignment: It would steal a bit of Saturn's gravity to slingshot past Uranus in 1985 and and then Neptune in 1989.
Spilker looked ahead at the years-long long gulf between Saturn and Uranus to start a different kind of mission.
"My two daughters, I tell them that their births are really based on the alignment of the planets," she said. "I was one of several 'Voyager moms' who looked at this and said, 'Ok, here's the time to start a family — our kids will be four or five years old by the time we get to the next milestone with Voyager.'"
Spilker, a friend, and other women they knew on the mission planned it out this way (and nature complied) to give their kids "a chance to grow up" before once-in-a-lifetime work again consumed most of their time.
The Voyager kids would grow up to play on softball teams together, become friends, and watch their parents unfurl the mysteries of the solar system — both on Voyager and future missions.
Spilker's work on Voyager, specifically her intense studies of Saturn's rings, would soon bring her to the next stage of her life and career: NASA's Cassini mission.
"The whole reason Cassini got started is that when Voyager 1 flew by Titan ... Voyager couldn't see through the haze to see the surface," she said.
In 1988, a group of scientists invited Spilker to join their team working on a return mission to Saturn, and they needed her expertise with creating an infrared system like Voyager's IRIS.
"They said, 'We know you specialize in rings, so do you want to come and be our ring leader?'" Spilker said, "and I said, 'Of course.'"
Cassini launched in 1997 and took seven years to close the roughly 890 million miles that separate Earth and Saturn.
In some ways, the journey was simpler for work-life balance than Voyager. The spacecraft orbited Saturn instead of making one brief flyby, for example. "There was always another orbit," Spilker said.
But everyone knew that Cassini wouldn't last forever, that Saturn had a bewilderingly complex system of moons, and that no one would grow younger.
"Every minute was precious," Spilker said. "Early on, when we hadn't really quite jelled yet as a team, there was a lot of people saying, 'My science is the most important science, and we should do that science.'"
Things "would get quite passionate and heated," Spilker said, but after these meetings the team would bury the hatchet and go out to lunch together. As the years rolled by, the Cassini team operated more as a family than a group of coworkers.
Cassini's main advantage, however, was sometimes a setback for staff and their families: The spacecraft was always alive and well, ready to take its next commands and make breakthrough discoveries.
"It was go go go go go all the time," Spilker said. "There was no stopping, really — no time between anything we were doing."
Adding staff helped soak up the extra work, yet Spilker offers some advice for anyone who finds themselves in a similar situation.
"Be very aware of spending time with your family," she said. "Things can wait until tomorrow."
Spilker added that this is much harder to do today than when she worked on Voyager and Cassini, since electronic devices now yearn for attention in our pockets and bring work into our homes — which is why she says prioritizing scheduling and structure with family are more vital than ever before to disconnect.
Year after year at Saturn, Cassini's discoveries left Earth spellbound.
The spacecraft dropped a lander on Titan in 2004 (the first landing on a moon other than Earth's), photographed hydrocarbon lakes on the moon, and found evidence of an ocean hiding below the world's crust.
Cassini also discovered six new moons and strange "propeller objects" in Saturn's rings; documented a spinning hexagon large enough to swallow several Earths at the planet's north pole; and flew through geysers of salty ocean water spraying out of cracks in Enceladus.
The probe took more than 453,000 images while orbiting the world for 13 years — far longer than anyone one on the team ever imagined the mission would last, Spilker said.
Cassini wasn't invincible, though. The probe left Earth with 6,900 pounds of propellant, which it used to change its orbit, for example, or point its antenna at Earth to transfer data. By September 2017, it had fewer than 90 pounds left in its tanks.
After 22 risky and unprecedented "Grand Finale" dives between the planet and its rings, the team said goodbye to Cassini on September 15.
NASA planned this act of "planetary protection" to keep the probe from accidentally crashing into Enceladus, shedding earthly microbes into its potentially habitable ocean, and contaminating the moon against a foolproof future detection of alien microbes that might exist there.
Before the probe was vaporized at Saturn, Spilker described her bond with the spacecraft and it discoveries.
"I've kind of given Cassini this personality, which probably reflects a lot of my personality, just as this hard-working, very dedicated spacecraft," Spilker said. "I think of Cassini as a she, with a nickname of Cassie, with those beautiful gold blankets."
Spilker added that she sometimes imagined sitting in the probe's saucer-shaped high-gain antenna — "right there as she dives between the rings and the planet." Thinking about the mission as a whole, however, her mind most often to turns to Enceladus.
"I wonder what it would it be like to stand on the surface near one of these jets, put out my hand, and have those icy particles fall into my hand — and then, quick, run over to a microscope and look for any signs of life," she said.
With the probe now a bunch of dust sprinkled across Saturn's cloud tops, Spilker hopes to redouble her dedication to Cassini's discoveries by launching a new mission to Enceladus.
NASA is currently reviewing a dozen $800 million proposals scientists have submitted to explore the solar system.
One primary target in the New Frontiers program, as its called, is Enceladus, so Spilker and her Cassini colleague Morgan Cable submitted a proposed spacecraft and mission to return.
"We've put together a proposal ... to go back to Enceladus with the kinds of instruments that you would need to address the questions about the habitability and is there life in the ocean of Enceladus," Spilker previously told Business Insider. "The mission's called Enceladus Life Finder."
She'll find out in December whether the proposal made the first cut, which would give her a year to more deeply study and flesh out a mission plan.
But there are 11 competing proposals, about half of which also propose a return to Saturn, and NASA will pick only one.
"Certainly, if my mission doesn't get selected, then I will be rooting for a mission to go back to the Saturn system," Spilker said. "Because as Cassini ends, part of me is saying, 'I need to go back.'"