A team of researchers at NASA's Marshall Space Flight Center in Huntsville, Alabama have created a simulation of the Apollo 12 lander engine plumes interacting with the lunar surface. The simulation animation illustrates the last 30 seconds of descent before the engine cut-off, and it shows the predicted forces that the plumes would exert on a flat computational surface. These forces are known as shear stress, which is the amount of lateral or sideways force applied over a specific area. It is the leading cause of erosion as fluids flow across a surface. The fluctuating radial patterns in the animation illustrate the intensity of predicted shear stress, with dark purple representing lower shear stress and yellow representing higher shear stress. The credits for this simulation go to Patrick Moran from NASA Ames Research Center and Andrew Weaver from NASA Marshall Space Flight Center.