New light shed on Titan’s dunes

The debates on Titan and Pluto are around how the dunes even got there.

Saturn’s largest moon, Titan, is an enigma with scientists unclear on how its vast expanses of dunes developed.

But a new study led by Monash University researchers and published today in Nature Astronomy provides some convincing new clues.

“We have no clear handle on how the dunes that encircle the moon Titan around its equator developed, especially where the sediment they are made out of came from,” said lead study author Dr Andrew Gunn, from the Monash University School of Earth, Atmosphere and Environment.

“The debates on Titan and Pluto are around how the dunes even got there,” he said.

“Our work provides the most robust predictions for what wind speeds must be in order to move sediment, placing a lower bound on the maximum winds each body’s atmosphere must achieve to make the dunes present on its surface.

“We also provide a measure for how fast sediment would break apart when moved in those conditions.”

Pairing these two results together is vital for identifying what sediment source for dunes is most likely.

The researchers compiled previously measured data from experiments on Earth and observations from space missions which describe the properties of sediments and the atmospheres of planetary bodies in our solar system, and data from experiments which directly measured the wind speeds required to move sediment.

Combining the theory and the data, the scientists produced predictions for planetary bodies of interest (Earth, Mars, Venus, Titan, Pluto and Triton) and then interpreted those predictions in light of active debates around those bodies.

“We show that sediment (not sand, either ice or organics, or a mix) cannot be from far away from where the dunes presently are, since our results indicate that the sediment particles can obliterate each other to dust as they collide when the wind blows them over relatively short distances,” explains Dr Gunn.

“Our study is significant because it shows for the first time that we can assess, for any given planetary body we have evidence of dunes on, how dynamic the atmospheres are, what its surface chemical composition is, and how sediments are produced, by just using first-principles physics—these are first-order questions when deciding on a planetary body’s potential for life and need for further study,” he said.

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