Limits on Kinetic Impact Deflection of Asteroids from Laboratory Hypervelocity Cratering and Disruption of Meteorites and Analogs

Successful deflection of a hazardous asteroid by kinetic impact requires cratering without disruption in order to avoid possibly leaving a large fragment of the asteroid on a collision course with Earth. A critical issue is the determination of the maximum change in velocity, and thus the orbital change, that can be imparted to asteroid material by a single hypervelocity kinetic impact while producing only cratering rather than fragmentation. Porosity, strength, mineralogy, and hydration influence the response of a target to hypervelocity impact. To investigate the maximum velocity that can be transferred by a single kinetic impact we performed a series of laboratory-scale hypervelocity impact cratering and disruption measurements on two types of anhydrous asteroid samples, the Northwest Africa (NWA) 869 ordinary chondrite meteorite and the NWA 4502 carbonaceous chondrite meteorite, using the NASA Ames Vertical Gun Range. Our results demonstrate that if disruption is to be avoided there is a factor of seven difference in the maximum velocity that can be imparted by a single kinetic impact between these two types of asteroid material. To investigate the effect of hydration on the maximum velocity transfer we impacted laboratory-prepared simulant of a hydrous carbonaceous meteorite target and determined that its behavior was similar to that of the NWA 4502 targets. Our results indicate that the maximum velocity change that can be imparted by a single kinetic impactor to this carbonaceous meteorite target is only ~0.27 m/s. This suggests that multiple kinetic impacts may be required for non-disruptive deflection of many Potentially Hazardous Asteroids, particularly the weaker carbonaceous asteroids.