Title: The shape and structure of cometary nuclei as a result of low-velocity accretion
Abstract: Collisions give comets their shape The shape and structure of comets are relicts of collision processes from long ago. Despite recent and ongoing spacecraft missions that offer direct measurements of cometary nuclei, it is difficult to test what is important in comet shaping. Jutzi and Asphaug ran ∼100 three-dimensional collision simulations across a wide range of target and impactor masses and trajectories. Slow and less violent collisions produced the layering and bi-lobed shapes of actual comets. Science , this issue p. 1355