planetary coasts

The Mississippi River delta and a possible river delta on Titan
Cassini SAR image of Ligeia Mare on Titan
Coastal geomorphology of Titan’s lakes

Titan, Saturn’s largest moon, is the only other solar system world we know of with active rivers and coasts. But Titan differs from Earth in some important and surprising ways: it has one-seventh the gravity, it’s incredibly cold, the landscapes are made of ice and organic compounds, and it has a methane cycle (natural gas) instead of a water cycle. If we apply what we know about Earth’s coasts to Titan, what can it teach us about planetary weather, climate, and habitability?

One unknown is whether Titan’s lakes have wind-generated waves like we do on Earth. Rose Palermo, jointly advised by Andrew Ashton (WHOI), is applying her expertise in coastal geomorphology to search for evidence of wave erosion in the shapes of Titan’s coasts. She built a computational model of coastal erosion by waves and other mechanisms and developed a technique for fingerprinting the erosional mechanism (wave-driven or not) from the resulting coastline shape. She is now testing this technique on Earth’s coasts, where we know the dominant erosional mechanisms, and applying it to Titan’s coasts to see if they bear the imprint of wave erosion. Una Schneck is pursuing signatures of wave action on sediment-dominated coasts by scaling theories from fluid mechanics and coastal sediment transport to Titan conditions. This work is in collaboration with Jason Soderblom, Juan Lora (Yale), and Alex Hayes (Cornell).

Where rivers on Earth meet coasts, they drop part of their sediment load, which can form river deltas. On Titan, there are several places where major rivers meet coasts – but almost none of them have river deltas. Sam Birch, Rose Palermo, and Una Schneck are chasing down the reasons why river deltas appear to be rare on Titan.