Now, new research published in Geophysical Research Letters and led by Mathieu Lapôtre models just how grains of sediment could form and exist on the large moon. On Earth, our sediment consists primarily of silicate rocks and minerals, which erode down into grains over very long periods of time. Silica is pretty hardy, after all, and doesn’t break down easily, so it takes erosion by wind and water to produce sand.

However, hydrocarbons are organic compounds, and they are more fragile than silicate grains, which means they should become dust over time. Lapôtre explains: As winds transport grains, the grains collide with each other and with the surface. These collisions tend to decrease grain size through time. What we were missing was the growth mechanism that could counterbalance that and enable sand grains to maintain a stable size through time.

To reconcile this mystery, the team turned to ooids on Earth, which are found in shallow tropical seas. Ooids are small, spherical grains made when calcium carbonate is removed from the water column and attaches to a silica grain, like quartz. The carbonate builds up in layers, growing in size, but that size is then kept in check by the erosion caused by waves and storms. This process leads to grains that stay consistent in size.

And that process could solve the mystery of Titan’s sand dunes lasting despite the more fragile grains. Lapôtre again explains: We were able to resolve the paradox of why there could have been sand dunes on Titan for so long even though the materials are very weak. We hypothesized that sintering – which involves neighboring grains fusing together into one piece – could counterbalance abrasion when winds transport the grains.

Further comparisons to existing data about Titan’s climate and sediment transport mechanisms match what could be happening to where it is happening on the moon. There are dunes at the equator, plains in the mid-latitudes, and labyrinthine terrain near the poles. Titan’s seasons drive the sedimentary cycle, just as happens on Earth and long ago on Mars.

As Lapôtre notes: It’s pretty fascinating to think about how there’s this alternative world so far out there, where things are so different, yet so similar.

More Information

Stanford University press release

“The Role of Seasonal Sediment Transport and Sintering in Shaping Titan’s Landscapes: A Hypothesis,” Mathieu G. A. Lapôtre, Michael J. Malaska, and Morgan L. Cable, 2022 April 1, Geophysical Research Letters