Rolling stones on Titan

Abstract

On Saturn's moon Titan the unique combination of low gravity, low-density surface materials (ices), and high atmospheric density may enable the wind to roll pebble, cobble, and perhaps even small boulder-size stones. If so, Titan's aeolian environment would be unlike that of Earth or Mars where wind is generally limited to transporting sand and dust much less than a couple of millimeters in size. To investigate the rolling-stone possibility we conducted a mathematical analysis constrained by conventional engineering and aerodynamic theory. We show that the minimum wind strength to cause saltation of sand on Titan is sufficient, under certain geological conditions, to also roll stones as large as ∼0.5 m diameter. Various features previously mapped on Titan have characteristics consistent with fields of wind-rolled stones, with the most compelling candidate being radar-bright ‘streak-like plains’ that are elongated parallel to nearby linear dunes. Possible implications for Titan science and the Dragonfly mission are considered.