Fran Bagenal’s Excellent Year

Pluto last summer, Jupiter this summer. Where to next for this veteran planetary scientist?

Planetary scientist Fran Bagenal. (NASA)
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Late Tuesday morning, University of Colorado scientist Fran Bagenal hurried to her car at the Jet Propulsion Laboratory in Pasadena to head for the airport and a flight home to Boulder.

Bagenal was feeling pretty good. A little more than 12 hours earlier, NASA’s Juno spacecraft, which she had spent years anticipating, had safely entered into a close-in polar orbit around Jupiter.

“The navigation was great, and we kind of knew it would be,” she said, smiling. “What we didn’t know was what the radiation belts would do, and luckily they were not as bad as we feared and we survived.”

For Bagenal, it was the second nail-biting planetary encounter in less than a year. She also was a co-investigator on last summer’s New Horizons Pluto flyby—one of only two people on the science teams for both of NASA’s recent missions to the outer solar system.

As a member of the Juno team, Bagenal chairs its magnetosphere working group. The magnetosphere, a massive magnetic bubble that bulges in front of the planet (toward the sun) and trails behind it millions of miles, traps and accelerates electrons to near-light speeds, wrapping the planet in searing radiation that could destroy Juno’s electronics if Juno’s engineers hadn’t gone to great trouble to protect them.

For Bagenal, her journey to explore Jupiter began nearly 40 years ago in the late ‘70s, when she was a graduate student at MIT. You could say her dreams of exploring the solar system started even earlier, when, as a teenager in rural England, she had watched TV broadcasts of the Apollo astronauts walking on the moon.

In graduate school she studied the physics of Earth’s upper atmosphere, so it seemed natural to work with the Voyager science team to study Jupiter’s magnetosphere. The twin Voyager spacecraft would eventually fly past Saturn, Uranus and Neptune before heading out of the solar system and into interstellar space. Bagenal was along for the whole tour.

After that, she worked on the Galileo mission to Jupiter, the (still running) Cassini mission to orbit Saturn, and most recently New Horizons.

As Juno entered orbit on July 4, it threaded the needle between Jupiter’s most powerful radiation belts and the top of the planet’s atmosphere. The spacecraft will orbit the planet 37 times over the next 20 months, braving the intense radiation each time.

Bagenal says Juno represents the culmination of her long career, and the return to Jupiter is designed to tackle questions that the Galileo mission left unanswered.

“Always Jupiter has been the archetype of a big planet with a magnetosphere dominated by the rotation of the planet,” she says. “This is a great opportunity to come back and answer these questions of how does the aurora get generated and how is the rotation of the planet coupled so this stuff that’s out there gets trapped in the magnetic field.”

Scientists are fairly certain that Jupiter’s interior is made of liquid metallic hydrogen, which conducts electricity and is the source of Jupiter’s powerful magnetosphere. “We’re pretty confident that’s the dynamo,” Bagenal says. “Where exactly the boundary is we’re not sure. What the flows are we’re not sure. That’s what Juno will tell us.”

After Juno, there will be a hiatus of new spacecraft exploring the outer solar system. NASA’s next Jupiter mission, still in development, is anticipated to explore Jupiter’s moon Europa sometime in the mid-2020s.

As she nears the end of her career, Bagenal still has her sights set on the outer solar system. While Jupiter and Saturn have gotten all the attention in recent years, she wants NASA to return to Voyager’s other targets. “Let’s go back to Uranus and Neptune!” she says, ever ready for another adventure.

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