Dione on Saturn (1 photo)

Dione is Saturn's fourth-largest moon, with an average diameter of 1,123 kilometers, composed primarily of water ice. This image was taken on June 21, 2015, by NASA's Cassini spacecraft.



The contrast between the light leading hemisphere and the darker trailing hemisphere is clearly visible—this is where the famous "white strands" (lat. "Wispy Terrain") are located: bright, fresh ice walls of tectonic faults stretching for hundreds of kilometers.

The surface is covered with countless craters of varying sizes, but in some areas, traces of tectonic activity are visible—mountains and scarps up to 1.5 kilometers high.

Analysis of Cassini data revealed that beneath Dione's icy crust, at a depth of approximately 100 kilometers, lies an ocean of liquid water. Its depth is estimated at 40-50 kilometers. Gravity measurements and analysis of the moon's libration (slow wobble) confirm that the icy crust "floats" on the liquid water surrounding the rocky core.

Thus, Dione is another member of the club of "worlds with subsurface oceans" in the Solar System and a promising target for the search for possible traces of life.