Scientists have relentlessly studied Saturn’s biggest moon, Titan. It’s a remarkable moon, unlike any other in the solar system, thanks to its highly stable bodies of surface liquid. The moon has long, winding channels and expansive, smooth plains typical of large liquid bodies, mostly made of methane. A new scientific study has dashed those expectations. Titan is devoid of river deltas, and this strange absence deserves retrospective exploration.
Titan is remarkable not only for its size, as the largest of Saturn’s moons, but for its fascinating, geologically-active landscape. What makes this world so special is that it actually has bodies of stable liquid on its surface. As a consequence, it provides an unparalleled chance for scientific study. The existence of flowing, liquefied methane on Titan’s surface had been a significant finding after several flybys by the Cassini spacecraft. During these missions, Cassini’s Synthetic Aperture Radar (SAR) was able to detect shallow, largely transparent methane lakes and rivers, illuminating Titan’s hydrological processes.
Titan’s dense, complex atmosphere results in an unusual environment. This allows the Cassini SAR to penetrate the thick cloud cover and gather critical data on Titan’s surface. To help interpret Cassini’s radar returns, researchers created a computer model that mimics how the radar would “see” various landforms on both Earth and Titan. By replacing Earth’s water with Titan’s liquid methane in the model, scientists aimed to identify similarities and differences in the geological features of both worlds.
On Earth, river deltas are iconic landforms that trap sediment across vast hinterlands, creating nutrient-rich wetlands. These deltas are irreplaceable ecosystems, nourishing everything from salmon to killer whales to sea birds. The researchers hoped to find correspondingly complex sedimentary features elsewhere on Titan, suggesting the presence of active geological processes and a dynamic environment. The lack of these deltas leads to a fundamental question about the moon’s landscape evolution: how was sediment transported across the lunar surface?
These channels on Titan show that liquid methane has moved over its surface. Yet, this dynamic flow of ice is not forming deltas like those we find on Earth. This difference might suggest other processes are at work in Titan’s environment than on Earth. Many things can explain the absence of sediment build-up. These are the viscosity of methane and a variation in climatic conditions.
The study’s results clarify some of Titan’s intricate hydrology, and prompt a return to the drawing board, urging scientists to broaden their perspectives on how they understand otherworldly landscapes. By comparing Titan’s landforms to those on Earth, researchers can make important inferences about the underlying processes that shaped them. They’re able to use Cassini’s perspective to create these wonderful comparisons.
