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LOS ANGELES – This data was like nothing, Margaret Kivelson and her team of physicists were never expected.
It was in December 1996 and the Galileo spacecraft had just flown to Europe, an icy moon of Jupiter. The readings returned to the Earth suggested a magnetic field emanating from the moon. Europa should not have had a magnetic field, yet it was there – and was not even headed in the right direction.
"It's unexpected," she recalls, as strange data arrived. "And it's wonderful."
This would be the most significant of a series of surprises from the Jovian moons. For Dr. Kivelson's team, the mission should not have been so exciting.
She and her colleagues had designed the magnetometer returning abnormal data. The work of the instrument consisted in measuring the massive magnetic field of Jupiter and all the variations caused by its moons. These results were likely to interest space physicists, but few others. Dr. Kivelson's instrument was never supposed to change the course of space exploration.
And then it happened. Dr. Kivelson and his team will soon prove that they have discovered the first underwater ocean of saltwater in an extraterrestrial world.
Mr. Kivelson, who turns 90 this month, is Emeritus Professor of Space Physics at the University of California at Los Angeles. For forty years she has been actively involved in almost every major NASA trip beyond the asteroid belt. She has a sense of ironic humor and her modesty conceals the breadth of her scientific achievements.
His team has transformed the way magnetometers are used in space missions, becoming an essential discovery tool. Having established, essentially, the art of ocean detection, the outer solar system is now a hot zone in the search for habitability.
Recently, Dr. Kivelson is a co-investigator working on the plasma instrument for the Europa Clipper, NASA's next big trip to the outdoor solar system. The satellite, scheduled for launch in 2022, will study the habitability of Jupiter's Moon Ocean. His work will help determine if life could exist by determining the depth and salinity of the ocean, as well as the thickness of the ice cover that covers it.
But the story began with Galileo's unusual encounters with Jupiter's moons. It turned out that incredible Europe had its own way of doing things.
"We had a lot of misconceptions," said Dr. Kivelson. Years after the first flyby, however, they found their answer.
Harvard and hydrogen
Dr. Kivelson was born in New York. His father was a doctor. His mother was a teacher. Margy, as her friends call her, excelled very early in mathematics.
"I liked that," she says. "I thought it was one of the easiest topics, and I knew that the opinion was not common."
She graduated and was accepted at Harvard, which formally excludes women and officially hands them over to Radcliffe College – a separate school without faculty. Harvard professors were crossing the commons repeat their lectures to women. "Women were not invited to Harvard classrooms," she said.
It was there that she discovered physics, which allowed her to use mathematics so that the answers would have a physical meaning.
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"I had the chance to start my studies at a time when physics was considered the most exciting field. It was just after the Second World War, "she said. "Physicists had saved the world with the atomic bomb and the radar. And all of a sudden, people have noticed that physics was not only a wonderfully fundamental discipline, but that it was also helpful. "
In his second year, there were no separate courses. In the wonderland of the atomic era, physics teachers no longer had the time to resume their classes. "It was ridiculous to give a lecture to 10 women for an hour, then to 400 men next," she said.
Not that the situation has suddenly improved for Harvard women. At the beginning of her physics studies, she was often the only woman in her classes.
In 1955 she joined RAND, a company created to provide research to the Department of Defense, including nuclear weapons research. She was instructed to work on an equation describing the state of hydrogen at a pressure equivalent to one million terrestrial atmospheres.
"There are two places where you experience this kind of pressure in hydrogen," she said. "One of them is in a hydrogen bomb, and the other is in the center of Jupiter."
His experience in theoretical physics and his potential expertise in celestial sciences led him to visit U.C.L.A. in 1967. Her research on RAND made her the local Jupiter specialist, and she soon became well known in space physics for her theoretical work on some of the most fundamental ideas in the field.
Fieldwork
Following the meeting between the Voyager spacecraft and Jupiter in 1979, scientists attending the American Geophysical Union conference in San Francisco debated how the moon Io could lead a mysterious stream million-amp between him and Jupiter.
Dr. Fran Bagenal, Professor Emeritus of Planetary Science at the University of Colorado, recalled Ms. Kivelson's contributions to this debate.
"This tiny little woman – who was not officially part of the Voyager team, but who was writing papers and thinking about the problem – was coming into the room, heading for the podium, lowering the microphone to be heard and talking. , and breaks everyone's ideas in the room, "said Dr. Bagenal about the scene at the conference.
"She ended up being right at the end," added Dr. Bagenal. "It was not to be played with. She knew his stuff.
When NASA announced what would become the Galileo mission to Jupiter, Dr. Kivelson was well placed to propose a magnetometer.
"I was very immersed in the science already available concerning Jupiter's magnetic field and the particulate environment," she said.
As she approached the deadline, she spent weeks working each day until midnight. When her instrument was chosen, "the champagne came out," she said. "Everyone was really happy."
Galileo came into orbit around Jupiter in 1995. The first major discovery of Dr. Kivelson and her team was an internal magnetic field located on Ganymede, Jupiter's largest moon.
Carol Paty, associate professor of earth sciences at the University of Oregon, said that no one really expected that such a small and cold object possessed chemistry, the thermodynamics and interior structure necessary to create its own magnetic field.
"Her discovery transformed the scientific understanding of the inner workings of planetary bodies," she said.
Then came the series of meetings between Europa and Galileo.
Geologists had suspected that the icy moon once had an ocean below the surface, but could not tell if it still existed or had frozen for a long time. It would always be a mystery if it were not the anomalous data received by the Galileo magnetometer.
Something strange was happening, and Dr. Kivelson and her miffed team found several ways to explain it. It was at this point that they had the idea that Europa's magnetic field was induced by Jupiter.
"It's the same principle that governs the metal detector in an airport," said Dr. Krishan Khurana, a geophysicist at the University of California. which was part of the discovery of the ocean.
When you walk through the door, a metal detector produces a high frequency magnetic wave. If there is a key in your pocket, the wave causes the passage of a current in the key, which in turn generates a small magnetic field. This induced magnetic field is what triggers the metal detector.
How could this work on a Jovian scale: As Europa travels through Jupiter's magnetic field, a current flows through a kind of underground conductor on the moon, creating an inverted miniature magnetic field to oppose the field of gravity. Jupiter. This actually triggered the Galileo metal detector.
The hypothesis was however inconclusive. It was possible for Europa to have its own intrinsic, strange magnetic field, which is found only as opposed to Jupiter's.
Jupiter's magnetic equator (as opposed to its geographical equator) is inclined by 10 degreessometimes Europe is above and sometimes below. The magnetometer team needed measurements when Europa was on the other side of the tilt.
If the magnetic field of the moon changed direction, it would mean that the field was induced by Jupiter – and thus had an inner conductor. The only thing that would suit the bill would be an underwater seawater.
Mr Kivelson argued in favor of the Galileo project for an overview of Europa in a specific orientation – it was not a slender request given the fact that spacecraft with limited resources flew over time. She triumphed and the January 2000 flyby revealed precisely the models her team predicted: a definitive proof of a world ocean.
"This is one of the most fundamental discoveries of global science," said Dr. Louise Prockter, director of the Lunar and Planetary Institute in Houston. "It generated a revolution, really."
Dr. Robert Pappalardo, scientist of NASA's Europa Clipper mission project, said the discovery had ramifications not only for Europa but for the entire solar system.
"It really made the pendulum swing towards the plausibility of the oceans in icy worlds," he said. "We moved quite quickly from" maybe "to" almost certainly " to "where else"?" It was a fairly fast transition, considering that the term "oceanic world" did not even exist at the time. It's now a class of objects, thanks to Margy's fundamental work. "
Ready for the next set of problems
Dr. Kivelson has not finished revealing the secrets of Jupiter.
In addition to her work on the upcoming Europa Clipper, she is contributing to the Jupiter Icy Moons Explorer mission of the European Space Agency, which is scheduled to launch in 2022. Her own research also focuses on a long-standing puzzle in the Magnetosphere of the gas giant linked to the mysterious heating. of plasma as it diffuses to the outside of Io.
She still works in her office every day and organizes a weekly dinner and meets Wednesday nights at U.C.L.A. for graduate students and teachers, a tradition that began 33 years ago.
Participants share their current research and discuss the latest advances in space physics. Criticism of each other's work can be cunning – sharp and lively, but unheated and antagonistic. Participants spend hours criticizing equations and models projected on a white screen. When they are challenged, they show up in front of a blackboard, leaving behind a chalky mixture of exponents, cosines and the Greek alphabet.
When laptops lined up at the table are lacking, scientists rush into their desks to pull out fifty-year-old textbooks and win a point or another. The humor punctuates the disagreements and the participants pass chocolate around the table while they work.
In a recent session, graduate student Steve Tomlinson was confronted with the unceasing questions of nine physicists as he presented research on the structures of coronal mass ejections from the sun.
Dr. Kivelson was at the heart of the case, seeking answers and further reflection, her questions leading Mr. Tomlinson to better explain his work.
"It seems like you have a very nice set of problems here," said Dr. Kivelson, satisfied with what she had seen after an hour of investigation and ready for the next presentation.
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