Saturn's largest moon, Titan, has a surface that doesn't make much sense. Images sent back by the cloud-piercing Cassini-Huygens spacecraft in 2004 showed a smooth surface that was barely touched by its extensive system of liquid methane rivers. And Titan has a strangely small number of impact craters from meteorites.
Put simply, Titan's surface doesn't look as old and weathered as it should. This has led astronomers to speculate that something strange is going on, from a geological perspective. Something strange, and yet also familiar.
One possibility is that erosion on Titan is extremely slow. Or alternately, some recent geological process has caused the older riverbeds and landforms to disappear — and that process could be one that we're very familiar with, here on Earth.
This is the conclusion of Taylor Perron, a Geology professor at MIT, and his graduate student, Benjamin Black. Their analysis and interpretation of Cassini-Huygens's photographs is set to appear in an upcoming issue of the Journal of Geophysical Research-Planets.
Like the Earth?
When looking at other moons in the solar system, Titan is uncharacteristically smooth. But like all the other celestial bodies in the solar system, it's about four billion years old. When looking at its surface, however, it looks like something much younger — perhaps something between 100 million and one billion years old.
Interestingly, there is another planet in the solar system with a surface that looks younger than it actually is: Earth. Our planet has not been immune to the impacts of asteroids, yet craters are few and far between. The reason for this is that Earth's continents are always eroding, or being covered with sediment. And according to Perron, it's very likely that Titan is going through a similar process.
Specifically, Perron suggests that geological forces such as tectonic upheaval, icy lava eruptions, erosion, and sedimentation may be at work. Unfortunately, given how little we know about Titan's surface, it may be a while before we're able to confirm exactly what mechanisms are at work here.
Ancient rivers with little impact
Perron and Black also took a look at the extensive river system on Titan, to see what effect they had on surface erosion. To do so, they mapped 52 prominent river networks from four regions on Titan, and then compared them to a model of river network evolution developed by Perron. The model takes such things into account as the strength of the underlying material and rate of flow through the river channels.
Based on this model, the researchers were expecting to see rivers transform from long, spindly threads into dense, treelike networks of tributaries. But instead, Titan's river network maintained their long and spindly composition, leading the researchers to conclude that these rivers play a very minor role in surface erosion.
Once again, Perron turned to Earth for a possible explanation. By looking at the volcanic terrain on the island of Kauai and recently glaciated landscapes in North America, the researchers discovered river networks very similar to what they saw on Titan — leading Perron to speculate that geological processes may have shaped Titan's icy surface in the recent past.
So, despite its methane- and nitrogen-infused atmosphere and its rivers of liquid methane, it appears that Titan is a lot more like Earth than we ever realized.
Top image via NASA/JPL/USGS via MIT. Inset image via Mike Zawistowski.