 Photographs and spectroscopic analysis by the Cassini–Huygens spacecraft show liquid ethane on the surface, which is thought to be mixed with liquid methane.The largest Titanean lake, Kraken Mare at 400,000 km2, is three-times the size of any lake on Earth, and even the second, Ligeia Mare, is estimated to be slightly larger than Earth's Lake Michigan–Huron.Jupiter's large moon Io is volcanically active, and as a result sulfur deposits have accumulated on the surface.