\label{fig:encounter_geometry} (Left) Mars Global Surveyor Mars Orbiter Camera image of crater showing dust devil tracks. Available at http://www.msss.com/mars_images/moc/2003/12/02/2003.12.02.R0901707.gif. (Right) Geometry of dust devil encounter. The blue circles show pressure contours, the y-axis runs along the devil’s velocity vector measured relative to the sensor \(\mathbf{\upsilon}\), and \(b\) is the closest approach distance between the barometer and the devil center. The shaded blue region shows the area of the surface carved out by the traveling \(P_{\rm th}\) contour. The inset shows a close-up of the encounter.