NASA's Cassini mission has resulted in several astounding discoveries, the latest being that Saturn's moon Mimas holds a body of water. Although
these Interior Water Ocean Worlds (IWOWs) are common in our solar system, Mimas' heavily crated exterior has tricked scientists into thinking otherwise.
IWOWs usually hint at some geologic activity due to their fractured surfaces, such as that of Enceladus and Europa. However, Mimas shows signs of none, meaning that it could belong to a new class of "stealth" ocean worlds "with surfaces that do not betray the ocean's existence," according to Dr. Alyssa Rhoden in a press release with Universe Today.
Tidal forces are in play when it comes to Mimas; interior structure. Alongside its rotational energy, Saturn's orbit stretches the small moon into its ellipsoidal shape, which in turn causes heating. This process involves a delicate balance in which the heating must be powerful enough to melt its interior into liquid, but not so that it melts the surface. IWOWs such as Mimas, which lack surface oceans, can be found over a wider range of distances since they do not rely on their stars to retain the temperatures required for liquid oceans.
Each discovery of an IWOW could signify the possibility of life. However, for life to happen, there has to be an active interface between water and rock. Rhoden expands on this, saying: "Evaluating Mimas' status as an ocean moon would benchmark models of its formation and evolution. This would help us better understand Saturn's rings and mid-sized moons, as well as the prevalence of potentially habitable ocean moons, particularly at Uranus. Mimas is a compelling target for continued investigation."