https://phys.org/news/2018-06-complex-depths-ocean-world-enceladus.html

During the spacecraft's incredible career, scientists discovered that 500 km–diameter Enceladus has a massive sub-surface ocean hidden underneath a thick icy crust, with evidence pointing to powerful hydrothermal vents on the seabed that mix up material from the moon's water-filled, porous core with the ocean water.

They detected mighty geysers releasing a mixture of water vapour and ice grains from the oceans into space through cracks – nicknamed 'tiger stripes' – in the moon's icy shell, providing material for one of Saturn's rings.