Titan, Saturn’s largest moon, is the only other planetary body in the solar system that currently hosts active rivers, lakes, and seas filled with liquid methane and ethane. The existence of these river systems was confirmed in 2007 by NASA’s Cassini spacecraft, leading scientists to study Titan’s mysterious liquid environment. Recently, MIT geologists have investigated Titan’s shorelines and demonstrated through simulations that the moon’s large seas have likely been shaped by waves, contradicting previous indirect and conflicting evidence of wave activity based on remote images.
The MIT team adopted a different approach by modeling the ways in which a lake can erode on Earth and applying their findings to Titan’s seas to determine the erosion patterns seen in Cassini’s images. They concluded that waves were the most likely explanation for the shoreline formations on Titan. While their results are not definitive, direct observations of wave activity on the moon’s surface are needed to confirm their findings. The presence of waves on Titan could give insights into the moon’s climate, such as wind strength, and help predict how the shape of its seas might evolve over time.
Wave-driven erosion was simulated by considering a variable known as fetch, which describes the physical distance from one point on a shoreline to the opposite side of a lake or sea. The team found that the shape of shorelines evolved differently depending on the erosion mechanism: uniform erosion resulted in inflated shorelines that widened evenly, while wave erosion mainly smoothed the exposed shorelines, leaving narrower and rougher surfaces. Comparisons with lakes on Earth supported their findings, showing significant differences in shape between lakes eroded by waves and those affected by uniform erosion.
The researchers focused on four of Titan’s largest and well-mapped seas, including Kraken Mare, Ligeia Mare, Punga Mare, and Ontario Lacus. By mapping the shorelines of each sea using radar images from Cassini, they found that all four seas fit solidly in the wave-driven erosion model, suggesting that waves are responsible for shaping Titan’s shorelines. Further analysis is underway to determine the strength of Titan’s winds required to create waves that erode the coasts and to identify the predominant wind directions based on the shoreline shapes.
Titan’s untouched system provides a unique opportunity to study fundamental aspects of coastal erosion without human influence, which may have implications for managing Earth’s coastlines in the future. The research was supported by NASA, the National Science Foundation, the USGS, and the Heising-Simons Foundation. Continued studies and direct observations will be crucial in confirming the presence of waves on Titan and understanding the complex interactions shaping the moon’s dynamic liquid environment.
