Enlarge / The lakes of Titan may have highly charged dunes on their shores. (credit: NASA)
Granular flows are, not to put too fine a point on it, horrible.
In some situations, they flow like a normal fluid, but a minuscule change will cause the flow to jam.
In the right situation, the particles will experience enough friction to pick up charge.

Then, if the particles are fine enough, the static discharge decorates the landscape with bits of your grain silo.
It’s not all bad, though: the movement of sand dunes and their singing in the wind is also part of granular flow. We all love it when inanimate bits of rock serenade us as we die of thirst.

And that’s just the Earth.

Titan also has dunes that seem to be oriented in the wrong direction relative to the prevailing winds, and scientists may have found the corner piece that helps them solve this puzzle: static electricity.
Dunes are not hills of sand; they are more like giant ripples that are oriented in a specific direction. On Earth, that direction is dictated by the prevailing wind.

The sand is blown about by the wind until it falls over the ridge on top of the dune and is protected beyond that.

Any protrusion that pokes out the wrong way is quickly etched away by the wind.
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