Original: Direct evidence was not obtained until 1995 when data from the Hubble Space Telescope and other observations had already suggested the existence of liquid methane on Titan , either in disconnected pockets or on the scale of satellite-wide oceans , similar to water on Earth .
Simplified: The Cassini -- Huygens team decided that the smooth areas are the hydrocarbon lakes they had been searching for , the first lakes found off Earth .