NASA’s Cassini spacecraft has just discovered and imaged a large river valley on Saturn’s moon Titan. The river is more than 200 miles long, spanning from its headwaters to the mouth of a large sea. This is the first time that images of a river system this large have been taken anywhere other than on the Earth.
The researchers are assuming that the river, “which is in Titan’s north polar region, is filled with liquid hydrocarbons because it appears dark along its entire length in the high-resolution radar image, indicating a smooth surface.”
“Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of this same Titan sea,” said Jani Radebaugh, a Cassini radar team associate at Brigham Young University, Provo, Utah. “Such faults — fractures in Titan’s bedrock — may not imply plate tectonics, like on Earth, but still lead to the opening of basins and perhaps to the formation of the giant seas themselves.”
You can see the image in its highest resolution here.
“Titan is the only other world we know of that has stable liquid on its surface. While Earth’s hydrologic cycle relies on water, Titan’s equivalent cycle involves hydrocarbons such as ethane and methane. In Titan’s equatorial regions, images from Cassini’s visible-light cameras in late 2010 revealed regions that darkened due to recent rainfall. Cassini’s visual and infrared mapping spectrometer confirmed liquid ethane at a lake in Titan’s southern hemisphere known as Ontario Lacus in 2008.”
“Titan is the only place we’ve found besides Earth that has a liquid in continuous movement on its surface,” said Steve Wall, the radar deputy team lead, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “This picture gives us a snapshot of a world in motion. Rain falls, and rivers move that rain to lakes and seas, where evaporation starts the cycle all over again. On Earth, the liquid is water; on Titan, it’s methane; but on both it affects most everything that happens.”
“The radar image here was taken on Sept. 26, 2012. It shows Titan’s north polar region, where the river valley flows into Kraken Mare, a sea that is, in terms of size, between the Caspian Sea and the Mediterranean Sea on Earth. The real Nile River stretches about 4,100 miles (6,700 kilometers). The processes that led to the formation of Earth’s Nile are complex, but involve faulting in some regions.”
Some background on Titan:
“Titan (or Saturn VI) is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.”
“Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter roughly 50% larger than Earth’s moon and is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter’s moon Ganymede, and it is larger by volume than the smallest planet, Mercury, although only half as massive. Titan was the first known moon of Saturn, discovered in 1655 by the Dutch astronomer Christiaan Huygens, and was the fifth moon of a planet apart from the Earth to be discovered.”
“Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan’s surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in the satellite’s polar regions. The surface is geologically young; although mountains and several possible cryovolcanoes have been discovered, it is smooth and few impact craters have been found.”
“The atmosphere of Titan is largely composed of nitrogen; minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes and seas (probably of liquid methane and ethane), and deltas, and is dominated by seasonal weather patterns as on Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan’s methane cycle is viewed as an analog to Earth’s water cycle, although at a much lower temperature.”
“The satellite is thought to be a possible host for microbial extraterrestrial life or, at least, as a prebiotic environment rich in complex organic chemistry with a possible subsurface liquid ocean serving as a biotic environment.”
Image Credits: NASA/JPL-Caltech/ASI; Titan via Wikimedia Commons