A new measurement of Jupiter's moon Europa shows its ice shell extends 29 kilometers thick above a vast saltwater ocean, creating a barrier equivalent to three Mount Everests stacked vertically. The finding presents a substantial obstacle for future missions hoping to reach the ocean beneath, where scientists believe conditions could support life.
Europa has long interested researchers because its subsurface ocean may contain more than twice the water found in all of Earth's oceans combined. The moon's icy surface shows cracks and ridges that suggest the ocean below remains active, with water potentially moving through the ice in some form. Scientists had hoped the ice shell might be thin enough in certain areas to allow future spacecraft to drill through and sample ocean water directly.
The 29-kilometer measurement changes calculations for how missions might access that ocean. Previous estimates had suggested the ice could be thinner in some regions, potentially making direct sampling feasible with current or near-future drilling technology. A barrier nearly 30 kilometers thick would require drilling capabilities far beyond what space agencies currently possess, even for robotic missions designed to land on the surface.
The study also suggests that direct fluid exchange between the deep subsurface ocean and the surface may be more limited than some scientists had theorized. If ocean water cannot easily reach the surface through cracks or other geological processes, it reduces the possibility that future missions could sample ocean material without drilling through the entire ice shell. This could affect plans for missions designed to search for biosignatures by analyzing surface ice.
Europa remains a priority target for astrobiology research despite the thicker ice measurement. NASA's Europa Clipper mission, designed to conduct detailed reconnaissance of the moon during multiple flybys, will gather more data about the ice shell's composition and thickness variations. That information will help determine whether any regions might offer easier access to the ocean below, and whether future lander missions equipped with ice-penetrating instruments could reach depths where ocean water might be present.