Grooves on asteroids: A prediction

The characteristics of the grooves on Phobos indicate that these features were formed by a large impact—an observation which implies that grooves may occur on other small bodies. Published data on fragmentation experiments suggest that the energy of the impact which produced the grooves on Phobos was in a critical range, strong enough to produce fracturing at large distances from the crater, but too weak to fragment the object. Other small bodies, such as asteroids, which have experienced an impact flux sufficient to include one such critical cratering event should show grooves, unless they have been fragmented subsequently by a more severe impact. We estimate that between $\text{1}\text{12}\text{th}\text{and}\text{1}\text{4}\text{th}$ of asteroids smaller than 100 km in diameter may have surface features resembling grooves associated with large impact craters. Several morphologically distinct types of grooves can be expected, depending on the thickness and composition of the regolith of the parent body. The full development of Phobos-like grooves seems to require a thick, and possibly volatile-rich, regolith—conditions which might obtain on certain C-asteroids.