Hydrothermal activity in Enceladus' core and the rise of organic-rich bubbles
Left: The interior of Saturn's moon Enceladus. The graphic shows the icy crust, which is thinner in the polar regions, below which sits an ocean. The moon has a porous rocky core. Water percolating into the core is warmed by contact with rock in the tidally heated interior. The heated water enters the ocean at hydrothermal vents located beneath the poles. Complex organics and rocky particles are entrained in the hydrothermal flow. Gas bubbles rising through the ocean collect organic material at their surface and transport them upward to the ice shell.
Centre: The oceanic water table lies inside cracks in the south polar ice crust. Bubbles of gas help bring organic material to the ocean surface, where it creates a thin film in the icy vents.
Right: When the bubbles burst at the surface they disperse some of the organics, along with a spray of salty ocean water. Droplets of the dispersed organic material become ice-coated when water vapour freezes on their surface, and along with the frozen spray of salty ocean water, are ejected in the plumes and then detected by Cassini.
Note that the insets at centre and right are rotated 180° with respect to the global view at left.