Some astronomers think that the two gas-giants do not sport solid surfaces secreted beneath their immense and heavy gaseous atmospheres, although others suggest that the jumbo-size duo do, indeed, harbor relatively small cores of rocky-icy stuff. The two other large inhabitants of the outer limits of our Sun's family are Uranus and Neptune, which are both classified as ice-giants, because they harbor large icy cores secreted deep down beneath their heavy, dense gaseous atmospheres which, though very massive, are not nearly as heavy as the gaseous envelopes possessed by Jupiter and Saturn.
The scientists also ruled out the possibility that the mysterious features actually exist on Titan's surface in the form of frozen methane rain or icy lava erupted from cryovolcanoes. Such surface features would show a different chemical signature and would be visible for much longer periods of time than the bright features observed in this study. The bright features were visible from time spans of only 11 hours to five weeks.
Cassini is an unmanned spacecraft sent to the Saturn system. It is the fourth space probe to visit the ringed planet, as well as the first to enter orbit. It has been studying Saturn and its many moons since arriving there in 2004.