Dust Devils on Titan
Brian Jackson, Ralph D. Lorenz, Jason W. Barnes, and Michelle Szurgot
Summarized by Lisette Melendez
What data were used? In 2019, NASA announced a brand-new mission: Dragonfly. The objective? To visit Titan, the largest moon of Saturn and the only place in our universe (besides Earth) where distinct evidence of surface liquid has been discovered. Titan’s environment is very similar to that of very early Earth, with a nitrogen-rich atmosphere and volcanic activity. By studying Titan’s chemistry, scientists can discover more about the origin of life itself. It’s a very exciting mission, but it’s important for scientists to prepare for all the different obstacles the rotorcraft will encounter on Titan’s surface, including hazardous weather phenomena like dust devils.
We’ve learned more about weather patterns on Titan through NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017. This study focuses on how dust storms are identified on other celestial bodies and what implications they hold for the Dragonfly mission. Cassini identified three regional dust storms within the equator near the “Shangri-La” dune fields that were chosen as Dragonfly’s landing spot. The study of these dust storms in Titan’s unique environment (with clouds and rain of methane!) can help us learn more about how they operate and life dust in the first place. This study also draws from observations by the Huygens probe for information on Titan’s temperatures and atmosphere.
Methods: In order to determine the weather conditions necessary for a dust storm on Titan, scientists need data on various atmospheric circumstances, such as temperature, elevation, and pressure. By analyzing the images and observations collected by Cassini and Huygens and combining these findings with data collected by observing dust devils here on Earth, scientists were able to model the surface conditions that were suitable for dust devil formation as well as the size of these storms. The study focused on dust devils on the equator because that’s where we have the most data available about Titan’s weather conditions.
Results: Many of the atmosphere conditions identified on Titan are favorable for the formation of dust devils. On Earth, dust devils are generally hindered by the presence of liquid because the increased particle cohesion (i.e., how sticky the particles are to one another) prevents wind from being able to lift the dust particles. Observations show that the equator of Titan is very arid and dry, with methane downpours only occurring in areas once every 10 Earth years. By looking at surface humidity levels measured by Huygens, it shows that the surface is too dry for even cloud formation. The abundance of dunes and dust storms provides further evidence that Titan has the ideal environment for dust devils.
However, there are some surface conditions on Titan that may reduce the occurrence of dust devils, including the possibility of insufficient wind speeds. Additional work is required to model typical speeds on Titan’s surface.
Why is this study important? This study is important because it helps predict the occurrence of dust devils on Titan when Dragonfly is scheduled to arrive in 2034. This study outlines what remains unknown about the formation of dust devils and how Dragonfly presents the opportunity to study wind-related phenomena in a novel environment.
The big picture: After analyzing the environment on the surface of Titan based on the data currently available, it is concluded that the dust devils will most likely not pose a threat to the Dragonfly rovercraft (since they are too slow in the given conditions). Nevertheless, the mission can provide crucial insight to the creation of dust devils and how frequently they occur on other celestial bodies. Dragonfly provides us the opportunity to learn so much more about extraterrestrial worlds, and we’re all very excited for its departure!
Citation: Jackson, B., Lorenz, R. D., Barnes, J.W., & Szurgot, M. (2020). Dust devils on Titan. Journal of Geophysical Research: Planets, 125, e2019JE006238. https://doi.org/10.1029/2019JE006238