Saturn’s largest moon Titan is a very alluring world. Aside from Earth, it is the only known place in the Solar System where liquid resides on its surface, in the form of rivers, lakes, and seas. Although these features are filled with liquid hydrocarbons (such as methane and ethane), beneath Titan’s crust of water ice is a layer of liquid, primarily consisting of water. Titan really is as sexy as they come.
Thanks to NASA’s Cassini spacecraft and ESA’s accompanying probe, Huygens, astronomers have been able to delve beyond the moon’s thick atmosphere to uncover its morphological features. Using radar observations from these missions, researchers have now suggested that abundant small depressions in the polar regions of Titan, close to its largest lakes, are in fact volcanic collapse craters. According to the study, published in the Journal of Geophysical Research: Planets, nested collapses, elevated ramparts, halos, and islands or floor mountains, provide evidence for explosive eruptions that may still be occurring.
“The close association of the proposed volcanic craters with polar lakes is consistent with a volcanic origin through explosive eruptions followed by collapse, as either maars or calderas,” co-author Charles Wood, Senior Scientist at the Planetary Science Institute, Arizona, said in a statement. “The apparent freshness of some craters may mean that volcanism has been relatively recently active on Titan or even continues today.”
To further their theory, Wood and fellow co-author Jani Radebaugh of Brigham Young University, Utah, looked closer to home. Multi-collapse craters similar to those observed on Titan, are also found on Earth and Mars. Whilst other landforms on Titan such as sand dunes, river valleys, and lakes result from atmospheric processes, these volcanic-like craters appear to be carved from within.
“We demonstrate that there is also evidence for internal heat, manifest at the surface as cryovolcanoes, made from melting the water ice crust into liquid water that erupts onto Titan’s surface,” Wood said. “These features are roughly round, with raised rims, and they sometimes overlap each other. They are consistent with the shapes of other volcanic landforms on Earth and Mars formed by explosion, excavation, and collapse.”
The fact that the depressions are only found at Titan’s north and south poles is no coincidence. Indeed, Wood and Radebaugh believe that the restriction of the suspected volcanism to these regions may be related to the “predicted warmer and thinner-than-normal crust at the low-elevation poles.” Their close proximity to liquid hydrocarbon lakes may also provide a clue as to its ammunition.
“That these features are at the polar regions, near the lakes of methane, may indicate methane, nitrogen or some other volatile may power them,” Wood said.