Markings on Europa’s surface suggest that the icy crust is at the mercy of the waters below. More importantly, Juno’s recent arrival reveals what plume activity is, which if real would allow future missions to sample the inner ocean without the need to land.
It’s been nearly two years since Juno made its closest approach to Europa, but its observations are still being analyzed. Remarkably, despite having only been orbiting Jupiter since 2016, the five images taken by Juno on September 29, 2022 are the first close-up images of Europa since the last visit by the Galileo spacecraft in 2000.
This represents a shocking omission from one of the Solar System’s most enigmatic worlds, but it could have provided a long baseline to see what has changed.
Europa is the softest object in the Solar System, thanks to constant resorption driven by its internal ocean. Nevertheless, it is featureless, and Juno found a few steep-walled craters 20 to 50 kilometers (12 to 31 miles) wide and indicating fracture patterns.True Polar Oscillation”.
“A true polar oscillation occurs when Europa’s ice shell detaches from its rocky interior, resulting in high stress levels on the shell, leading to predictable fracture patterns,” said Dr Candy Hansen of the Planetary Science Institute. Report.
The idea behind true polar oscillations is that the shell over Europa’s inner ocean rotates at a different rate than the rest of the moon. It is thought that currents within the ocean affect the movement of the shell, moving the water below and dragging the shell with it. The currents are driven by heating within Europa’s rocky core as the gravitational pull of Jupiter and its larger moons turns Europa into a giant pressure ball.
In the process, the interactions between the ocean and the ice sheet stretch and contract, creating the cracks and ridges seen since Voyager 2 visited.
Hansen is part of a team examining Juno’s images of Europa’s southern hemisphere. “This is the first time these fracture patterns have been mapped in the Southern Hemisphere, suggesting that the effect of true polar oscillations on Europa’s surface geology is more extensive than previously identified,” the scientist said.
Not all changes in Europa’s maps are the result of internal ocean currents. Even NASA seems to fall for optical illusions. “The Crater Quern is no more,” Hansen said. “Once thought to be a 13-mile-wide impact crater — one of Europa’s few documented impact craters — the Quern is revealed in Junocom data as a set of intersecting ridges that form an oval shadow.”
However, Juno gives more than it takes. The team is excited by calling the platypus for its shape, rather than its features that shouldn’t go together. Ridge formations on its edge appear to be collapsing into it, and the team thinks the process may be caused by pockets of salt water that have partially infiltrated the ice shell.
This feature is named by planetary scientists who have never seen a real platypus, outlined in yellow with the ridge area in blue.
Image credit: NASA/JPL-Caltech/SwRI
Such pockets would be exciting indirect targets for the Europa Clipper probe, but even more interesting are the dark smudges deposited by cryovolcanic activity.
“These features indicate present-day surface activity and the presence of subsurface liquid water on Europa,” said Heidi Becker of the Jet Propulsion Laboratory. Such activity has been confirmed in Enceladus’ geysers, but there is conflicting evidence as to whether it is currently occurring on Europa.
Such an operation could sample signs of life in the inner ocean without landing, drilling, flying through a plume and collecting some ice.
Currently, the polar tide may cause very modest changes in the locations of features on Europa’s surface, but there is evidence that a change of more than 70 degrees occurred millions of years ago.
