Europa is the softest solid object in our solar system, thanks to its thick icy shell. But beneath its smooth exterior, Jupiter’s fourth largest moon appears to harbor a secret — namely, deep salty oceans with exciting potential for alien life.
This ocean makes Europa a prime target for scientific study, including two separate orbital missions scheduled to launch toward Jupiter in the next two years.
And while it will take several years for one of the probes to arrive, scientists are already highlighting Europa in other ways, drawing insights from telescope observations, previous flybys of probes, laboratory experiments, and computer simulations.
in a new studyResearchers from the Jet Propulsion Laboratory (JPL) at the California Institute of Technology in the United States and the University of Hokkaido in Japan used a NASA supercomputer to examine Europa’s little-known anomaly: why does the ice crust rotate faster on the inside?
According to their research, the asynchronous rotation of the surface may be caused by ocean currents pushing up from below. This is a major discovery, explains lead author and JPL researcher Hamish Hay, who is currently at the University of Oxford. It’s a revelation that could provide new clues about what’s going on underneath.
“Prior to this, it was known through experimentation and laboratory modeling that the heating and cooling of Europa’s oceans might be driving the currents,” Hay said. He said. “Now our results highlight a connection between the oceans and the circulation of the ice crust that had never been thought of before.”
The ice shell floats in Europa’s oceans, so it can rotate independently of the other oceans moon, including the oceans, the rocky interior, and the metal core. Scientists have long suspected this, but the driving force behind the projectile’s rotation has remained a mystery.
Europa is subject to tidal bending by Jupiter, which deforms it moon with great traction. This massive tug of war caused cracks in Europa’s icy crust and likely generated some of the hot mantle and core.
Combined with the heat energy released by radioactive decay, warmth from Europa’s interior is thought to rise across the ocean toward the frozen surface like a pot heating water on a stove.
Combined with Europa’s circulation and other factors, this vertical temperature gradient would trigger quite strong ocean currents.
The study predicts that these currents could be strong enough to move the global cryosphere. No one knows exactly how thick the crust is, but estimates range from approx 15 to 25 kilometers (15 miles).
While scientists knew Europa’s cryosphere was likely rotating on its own, they focused on Jupiter’s gravitational influence as a driving force.
“To me, it was completely unexpected that what was going on in the ocean circulation was enough to affect the ice crust. It was a big surprise,” he said. He said Study co-author and Europa Clipper project scientist Robert Pappalardo of NASA’s Jet Propulsion Laboratory.
“And the idea that the cracks and ridges we see on Europa’s surface could be linked to the ocean cycles beneath – geologists don’t usually think, ‘Maybe the ocean did it,’” Add.
The researchers used a NASA supercomputer to build a complex simulation of Europa’s oceans, borrowing techniques already used to model Earth’s oceans.
This model allowed them to study details of Europa’s water circulation, including how this pattern is affected by ocean heating and cooling.
The main focus of this research is drag, or the horizontal force of the ocean that pushes the ice above it. By analyzing the drag in their simulations, the researchers found that some of the faster currents could generate enough drag to speed up or slow down the rotation of Europa’s ice sheet.
While this effect depends on current speed, the researchers note that Europa’s internal heating can vary over time. This can lead to a similar difference in the speed of ocean currents, which in turn causes a faster or slower rotation of the ice crust.
As well as helping us understand Europa, this research can also be applied to other ocean worlds, the researchers note, where surface features can provide clues about the hidden waters below.
“Now that we know about the possible fusion of the inner oceans with the surfaces of these objects, we can learn more about their geological history as well as that of Europe,” Hay He said.
European Space Agency Jupiter Ise Satellite Explorer JUICE is scheduled to launch in April 2023, to begin its journey to study the three moons of Jupiter that carry large oceans: Ganymede, Callisto and Europa.
At the end of 2024, NASA plans to launch a rocket European cutter orbiter, which will make about 50 close flybys to investigate the moon’s habitability. According to the authors of the new study, it may be possible to accurately measure how fast Europa’s ice sheets are rotating.
The study has been published in Planet JGR.
