Saturn’s moon Titan continues to amaze scientists and onlookers. Titan is the only planetary body, besides Earth, known to have a stable liquid environment on its surface. Unlike Earth, whose liquid is water, Titan’s liquid is a mixture of hydrocarbon molecules like ethane and methane.
Liquid was confirmed to exist on Titan since 2009, but scientists had identified several features thought to be seas or lakes much earlier. In 2007, Cassini discovered a vast sea, which is now named the Kraken Mare, near Titan’s north pole. The Kraken Mare is thought to be about the size of the Caspian Sea on Earth. Several other large seas and lakes cover the arctic region of Titan.
Cassini’s latest discovery flows into the Kraken Mare—an enormous river system stretching 400 km across Titan, emptying into the sea. Scientists looking over Cassini’s findings have compared its complexity to that of the Nile River on Earth.
The river is thought to follow, for at least some of its path, a fault, a crack in Titan’s bedrock. Such faults are thought to be the cause of other, smaller rivers and perhaps the origin of the large seas as well.
Scientists justify their description of this formation as a river of liquid because radar images of its surface come back very dark, indicating an extremely smooth surface.
The full hydrologic cycle of Titan has not been completely studied yet, but its resemblance to Earth’s own cycle is stunning. Not only does the cold, distant moon have lakes and rivers, but it has active weather as well. Regions Cassini has examined on different passes sometimes look darker during a later pass. Scientists believe the change in albedo is due to rain having soaked the ground. Scientists have even detected entire lakes formed due to rainfall.
So, is rain the source of this extraterrestrial version of the Nile? No one yet knows, and there are many more questions to be answered about Titan.