NASA’s Cassini spacecraft has captured the first image of a 200 mile long river on one of the moon’s orbiting Saturn, Titan.
The liquid river, the first observed on another planetary body, stretches more than 200 miles (400 kilometers) from its headwaters to a large sea.
Using Cassini’s radar imaging instruments, NASA scientists were able to determine that the strange geological feature is likely a river as the dark, smooth surface within the meanders and channel suggest the presence of a liquid. The radar image, according to NASA, was taken on September 26, 2012, and it details Titan’s north polar region, where the river valley flows into Kraken Mare, a sea that is similar in size to the Caspian Sea and the Mediterranean Sea.
Describing the finding, NASA astronomers say the river system could provide them with a better picture of the planet’s fractured surface. Recent analysis suggests that Titan’s internally generated heat keeps the moon’s oceans from freezing, possibly allowing for isolated environments in which microscopic lifeforms thrive.
“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, Cassini radar team associate at Brigham Young University. “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.”
The discovery of the river likely increases the odds that Titan hosts vast bodies of liquid all across its surface. Astronomers have long posited that Titan could serve as a hotbed for microscopic lifeforms. Titan is the only other world we know of that has stable liquid on its surface, and while Earth’s hydrologic cycle relies on water, Titan’s equivalent cycle involves hydrocarbons such as ethane and methane, according to NASA.
The latest discovery comes just years after NASA released images from Cassini’s visible-light cameras in late 2010 that revealed regions throughout the planet that resembled darkened patches due to recent rainfall. That discovery followed an even earlier finding regarding Cassini’s infrared mapping spectrometer that confirmed liquid ethane at a lake in Titan’s southern hemisphere known as Ontario Lacus in 2008.
In a statement released by the U.S. space agency on Wednesday, NASA officials say the latest image could serve as the first step in better understanding of the moon’s icy makeup. Titan has long intrigued scientists because of its similarities to Earth. Like Earth, Titan appears to have a layered structure, crudely similar to the concentric layers of an onion. The rock in the core is thought to contain radioactive elements left over from the formation of the solar system. As in Earth’s core, when those elements decay, they generate heat. On Titan, that heat is crucial to keeping its ocean from freezing solid.
“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 $3.2 billion Cassini mission is a collaboration involving NASA, the European Space Agency and the Italian Space Agency. It launched in 1997 and arrived at the Saturn system in 2004.