EXPERTS ADVISORY

The launch window will soon open for NASA’s Europa Clipper, the organization’s latest mission to Jupiter’s system of moons.

Once the spacecraft launches between Oct. 10 and Nov. 6, it will begin its journey to Europa, a moon with a salty ocean underneath an icy crust. With Europa Clipper, University of Michigan researchers will help determine whether that ocean could support marine life.

U-M experts can discuss how they originally discovered Europa’s hidden ocean using magnetic field measurements made by Galileo, which launched to Jupiter in 1989. They can also discuss how Europa Clipper’s new instruments will help determine the ocean’s depth and salinity, two key parameters of habitability.

Margaret Kivelson is a research professor of climate and space sciences and engineering at and a professor emerita at the University of California, Los Angeles. She is the science team leader for Europa Clipper’s magnetometer, an instrument that will measure magnetic fields at Jupiter and Europa, and a co-investigator of Europa Clipper’s Plasma Instrument for Magnetic Sounding. She was also the principal investigator of the magnetometer on Galileo—the instrument that allowed scientists to discover Europa’s ocean in the first place.

She can comment on how she helped discover Europa’s subsurface ocean using data from Galileo.

“For most planets and moons with magnetic fields, their magnetic and geographic poles point to almost the same places. But when Galileo got to Europa, we saw that the magnetic poles were cutting across the moon,” she said. “An electrical current flowing in a conductive layer on the moon could explain that magnetic field, but only if it was very close to the surface. Since Europa is covered with a 100-kilometer-thick shell of water ice, a salty ocean was the best explanation.”

Kivelson also went to graduate school at Radcliffe College back when it was emerging from an era when it had been a campus for women to be educated in separate classes by Harvard faculty. She can comment on what it was like to attend some of Harvard’s first co-ed physics lectures and other classes.

Contact: [email protected], [email protected]

Xianzhe Jia is a professor of climate and space sciences and engineering who has been working with Kivelson since he was in graduate school. He is also the deputy science team leader for Europa Clipper’s magnetometer and a co-investigator of Europa Clipper’s Plasma Instrument for Magnetic Sounding.

He and Kivelson can both comment on how Europa Clipper will determine the thickness of Europa’s ice shell and the depth and salinity of Europa’s ocean. These measurements provide key constraints on Europa’s interior structure as well as how water is exchanged between the ocean and the moon’s surface, all of which are highly relevant to understanding its habitability. If the ocean is too far below Europa’s surface, or doesn’t touch Europa’s rocky mantle, it is less likely to collect the chemical ingredients for a primordial soup from which life can emerge.

“The electric currents that create Europa’s induced magnetic field are driven by Jupiter’s time-varying magnetic field, which changes in strength and orientation at Europa’s location over the course of Jupiter’s ten-hour day and as Europa orbits around the planet,” he said.

“Galileo flew by Europa 12 times, which was only sufficient for viewing how Europa’s induced magnetic field changes over Jupiter’s day. That cycle told us about the integrated effect of the ocean’s thickness and salinity on Europa’s induced magnetic field. We couldn’t get those two ocean parameters separately. But Europa Clipper will fly past Europa almost 50 times and get as close as 16 miles above the surface, allowing us to measure the longer cycle associated with Europa’s orbit around Jupiter. We can combine both of these signals to separately determine the ocean’s thickness and salinity.”

Contact: [email protected]