Giant Unexpected Ice Corridor Discovered On Titan

This near-infrared, color view from Cassini shows the sun glinting off of Titan's north polar seas. Image credit: NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho 

Titan is the largest moon of Saturn and the second largest in the Solar System. It’s a cold world with a thick atmosphere, where liquid methane rains down and forms lakes and rivers. The latest analysis of Cassini data highlights an unexpected structure not seen before.

Researchers found a 6,300-kilometer-long (3,900-mile), ice-rich corridor of bedrock across the moon’s surface. This corridor extends for a length equivalent to 40 percent of Titan’s equator and is found mostly around the tropical region.

The team, led by Professor Caitlin Griffith, was looking for evidence of cryovolcanism, geological structures that would erupt ice like volcanos on Earth eject lava. A single region, called Sotra, is known to show cryovolcanic features and researchers wanted to find evidence for smaller, subtler cryovolcanos. Instead, as reported in Nature Astronomy, they found this huge ice belt.

“This icy corridor is puzzling, because it doesn’t correlate with any surface features nor measurements of the subsurface," Griffith, from the University of Arizona, said in a statement. "Given that our study and past work indicate that Titan is currently not volcanically active, the trace of the corridor is likely a vestige of the past. We detect this feature on steep slopes, but not on all slopes. This suggests that the icy corridor is currently eroding, potentially unveiling presence of ice and organic strata.”

Three orientations of Titan's globe. The icy corridor is mapped in blue. NASA/JPL-Caltech/Space Science Institute

Griffiths and her team used 13,000 spectral images collected by the Cassini mission and a technique called principal component analysis. This allowed her to get incredible insights into the surface and subsurface composition of Titan. The researchers found diverse and intriguing organic deposits in certain regions, formed by the interaction between sunlight and compounds in the atmosphere.

“Both Titan and Earth followed different evolutionary paths, and both ended up with unique organic-rich atmospheres and surfaces,” Griffth added. “But it is not clear whether Titan and Earth are common blueprints of the organic-rich of bodies or two among many possible organic-rich worlds.”    

Both the icy corridor and the organic deposits seem to have formed in a bygone age for the moon, but their properties might help us understand the current evolution of Titan. An enduring mystery is Titan’s source of methane. The methane is broken down by sunlight and accumulates on the surface as complex molecules. Methane lakes contribute by evaporating, but it appears not to be enough. Researchers were hoping to find cryovolcanos that release underground deposits of methane, but since they don’t seem to be there, the mystery continues.

The researchers are now planning to explore the poles with this technique. That’s where the majority of methane lakes reside.  

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