Several theories could explain disappearing bright spot in Titan sea

BBC : On 10 July 2013, sensors aboard the Cassini spacecraft spotted a bright mark in the otherwise dark area that is one of the liquid methane and ethane seas on Saturn’s moon Titan. It had not been present in previous images the orbiter took and was absent again on the craft’s next pass over the area 16 days later. Because the disappearance was so quick, it is unlikely to have been caused by volcanic activity. Jason Hofgartner of Cornell University in New York and member of the Cassini team proposes that the mark was caused by an iceberg, a release of gas, waves, or a suspension of some other solid matter. According to Hofgartner, all of the possibilities are equally likely. If the spot had been a volcanic island, it would have been the first direct evidence of vulcanism on Titan. Continued observations of the moon will possibly reveal similar events with enough detail to allow for a narrowing of the options.