The moon Ganymede (right) orbits the giant planet Jupiter in this artist's rendering. Scientists say a saline ocean lurks under the moon's icy crust. NASA/ESA hide caption toggle caption NASA/ESA The Two-Way Moon River? No, It's An Ocean On One Of Jupiter's Moons! March 12, 2015 Scientists announced in a NASA teleconference that the biggest moon in our solar system has a salty ocean hidden below its icy surface.