Ranger and Apollo S-IVB spacecraft impact craters

Abstract

Numerous spacecraft have impacted the surface of Moon during the last several decades of lunar exploration. These impacts fall into two categories: relatively high-angle impacts formed by spacecraft on direct trajectories from the Earth and low-angle impacts formed by spacecraft in lunar orbit. The craters produced by the Ranger spacecraft and the Apollo S-IVB boosters are discussed here. The Ranger spacecraft had a mass of ~370kg (816lb.), impacted at 2600kms−1 and formed craters ~14–15m in diameter. The S-IVB boosters had masses of ~14,000kg (30865lb.), impacted at ~2600kms−1 and formed craters ~35m in diameter. These impacts are relatively unique due to the low bulk-density of the impactor (28 and 700kgm−3, respectively the S-IVB and Ranger spacecraft). Craters produced by the impact of the Ranger spacecraft are similar to other lunar mare craters in which the excavation process was impeded by the underlying solid basalt. Craters produced by the S-IVB impacts are non-circular and exhibit an elongate central mound. It appears that the S-IVB crater excavation also interacted with the basalt but in a more complicated manner than for the Ranger craters. Ejecta and rays associated with these craters are asymmetric and indicate that the excavation flow field varied with time and was not symmetric about the trajectory direction.