Scientists analyzing NASA’s latest Juno spacecraft observations estimate that Europa, Jupiter’s enigmatic moon, may contain a salty ocean beneath its ice shell holding more than twice the combined water of all Earth’s oceans. The average thickness of Europa’s subsurface ice layer in the observed area was estimated at about 29 kilometers.

On September 29, 2022, Juno flew just 360 kilometers above Europa. Its Microwave Radiometer examined microwave radiation at different wavelengths to determine the ice layer’s thermal properties. Europa has a diameter of 3,120 kilometers, smaller than Earth’s Moon, but scientists estimate its buried ocean could be 60 to 150 kilometers deep. Ice thickness may vary across different regions.

The findings do not settle whether Europa can support life, because water alone is insufficient. Chemical energy, biologically necessary materials, and exchange between the seafloor and ice-covered surface are also needed. NASA’s Europa Clipper, launched on October 14, 2024, is expected to reach Jupiter’s orbit in April 2030 and conduct about 50 missions around Europa using radar, cameras, spectrometers and magnetic measurements.