Wind tails and moats on different planetary bodies. (a) Wind tails associated with vegetation acting as obstacles at Grand Falls Dune Field, Arizona, USA (Photo: D. Tirsch). (b) Boulder “Barnacle Bill” at the Mars Path Finder landing site. This 43-by-22-cm-sized rock is associated with a distinctive moat to its right and a wind tail to its left (subset of MPF image 81008 with parts of the Sojourner rover at the lower right). (c) 5-m-sized boulder at Philae’s first touchdown site “Agilkia” on comet 67P. White dashed lines trace the shape of the moat and the wind tail associated with this boulder (subset of ROLIS image ROL_FS3_141112153316_336_02). (d) Sketch showing the typical shape of a moat and a wind tail associated with an obstacle. Blue arrows indicate the wind direction in panels a, b, and d as well as the transport direction of air fall particles in panel c.