The research reveals a new explanation for how the icy crust of Jupiter’s moon Europa rotates at a different rate than its internal rotation. NASA’s Europa Clipper will take a closer look.
NASA scientists have strong evidence that Jupiter’s moon Europa has an inner moon Ocean beneath its icy outer surface coincidenceA huge body of salt water orbits the moon’s rocky interior. New computer modeling suggests that water may actually be pushing the icy crust along, possibly speeding up and slowing the rotation of the moon’s icy crust over time.
Scientists have known that Europa’s shell is probably free-floating, spinning at a different rate than the ocean below and the rocky interior. The new modeling is the first to show that Europa ocean currents It may contribute to the circulation of its ice crust.
A key component of the study involved calculating drag – the horizontal force exerted by the Moon’s circumference on the ice above it. The research hints at how the force of the ocean flow and its pull against the ice sheet might explain some of the geology seen on Europa’s surface. Cracks and ridges can result from the ice crust slowly stretching and collapsing over time as it is pushed and pulled by ocean currents.
Hamish Hay, a researcher at the University of Oxford and lead author of the study published in the journal Journal of Geophysical Research: Planets. Hay conducted the research while a postdoctoral research associate at NASA’s Jet Propulsion Laboratory in Southern California. “Now our results highlight a coupling between ocean and ice crust circulation that had not been thought of before.”
It may also be possible, using measurements collected by NASA’s upcoming Europa Clipper mission, to determine precisely how fast the ice crust is spinning. When scientists compare the images collected by the Europa Clipper with those taken in the past by NASA’s Galileo and Voyager missions, they will be able to examine the locations of ice surface features and possibly determine whether the location of the moon’s icy crust has changed over time.
for decades, Planetary scientists We have debated whether Europa’s icy shell might be spinning faster than the deep interior. But rather than linking it to the movement of the ocean, the scientists focused on an outside force: Jupiter. They hypothesized that while the gas giant’s gravity is pulling on Europa, it is also pulling on the moon’s crust and causing it to rotate a little faster.
“For me, it was completely unexpected that what was happening in the ocean circulation would be enough to influence the ice crust. That was a big surprise,” said co-author and Europa Clipper project scientist Robert Pappalardo of JPL’s Robert Pappalardo. “And the idea that the cracks and ridges we see on Europa’s surface could be linked to the ocean cycle below — geologists don’t usually think, ‘Maybe it’s the ocean that’s doing it.'”
The Europa Clipper, now in the assembly, test, and launch phase at JPL, is scheduled for launch in 2024. The spacecraft will begin orbiting Jupiter in 2030, and will use its suite of sophisticated instruments to gather science data as it flybys the moon about 50 times. The mission aims to determine if Europa, with its deep inner ocean, has conditions that could be suitable for life.
Like a pot of water
Using techniques developed to study Earth’s circumference, the paper’s authors relied on NASA supercomputers to make large-scale models of Europa’s ocean. They explored the intricacies of how water circulates, and how heating and cooling affect this motion.
Scientists believe that Europa’s inner ocean is heated from below, by radioactive decay and tidal heating within the moon’s rocky core. Like heating water in a pot on a stove, Europa’s warm water rises to the top of the ocean.
In the simulations, the rotation initially moved vertically, but the moon’s rotation as a whole caused the flowing water to deflect in a more horizontal direction—in the east-west and east-west currents. By including clouds in their simulations, the researchers were able to determine that if the currents are fast enough, there may be enough drag on the ice above to speed up or slow down the spinning speed of the envelope. The amount of internal heat—and thus circulation patterns in the ocean—may change over time, potentially speeding up or slowing the rotation of the ice crust above.
“The work could be important in understanding how the rotational speeds of other ocean worlds have changed over time,” Hay said. “Now that we know about the possible coupling of the inner oceans with the surfaces of these bodies, we may learn more about their geological history as well as that of Europe.”
Europa Clipper’s main science goal is to determine whether there are places beneath the surface of Jupiter’s icy moon, Europa, that could support life. The mission’s three main science goals are to understand the nature of the ice crust and the ocean beneath it, along with its composition and geology. The mission’s detailed exploration of Europa will help scientists better understand the astrobiological potential of habitable worlds beyond our planet.
HCFC Hay et al, Turbulent drag at the ice-ocean interface in Europe in a simulation of rotating convection: implications for asynchronous rotation of the ice crust, Journal of Geophysical Research: Planets (2023). DOI: 10.1029/2022JE007648
Jet Propulsion Laboratory
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