Introduction: impact cratering has been and continues to be the dominant macroscopic surface process on the majority of solid bodies in the solar system. Impacts form craters that act as subsurface…

Winona State University, an educational institution, was awarded a $242,443.00 grant from the National Aeronautics and Space Administration (NASA) to conduct research on the effects of target topography and heterogeneity on the impact cratering process. The goal of this research project is to investigate how regional target characteristics, such as rough terrain and subsurface heterogeneity, impact the excavation, growth, and modification of impact craters. The research will utilize specialized experimental techniques at the NASA Johnson Space Center to observe the cratering process in real-time. The findings will be used to adapt existing crater scaling relationships to better describe the behavior of complex targets. This grant-funded research project is relevant to understanding the evolution and modification of planetary surfaces throughout the solar system and does not have a set-aside designation.

Introduction: impact cratering has been and continues to be the dominant macroscopic surface process on the majority of solid bodies in the solar system. Impacts form craters that act as subsurface probes, excavating subsurface material and depositing IT outside of the crater, generating and mixing the regolith, and launching future meteorites. Current knowledge of the excavation and modification of impact craters from experiments and numerical models is limited primarily to cases of flat, homogeneous, and uniformly layered targets. Thus, existing experimentation and numerical modeling provide only first-order guidance when considering the effects of impact in a realistic environment: rough terrain that can be as heterogeneous in structure at depth as IT is irregular at the surface. Science goals and objectives: the goal of this proposed work is to take the next logical step in experimental impactcratering studies by investigating the effects of regional target topography and strength heterogeneity on the impact process. In particular, we will identify how these variables affect the excavation of materials from a growing impact crater, the growth and modification of the crater shape, and the final crater morphometry. We will use these results to adapt and modify existing craterscaling relationships to describe the behavior of such complex targets. Methodology: impact-cratering experiments will be performed at the experimental impact laboratory at NASA johnson space center. Two non-invasive experimental techniques will be used to observe the cratering process in real time the ejection- velocity measurement system (evms) and a real-time profiling system (rtps). The evms projects a vertical laser plane through the impact point and perpendicular to the target surface. This laser plane is strobed at a known rate while a CCD camera images the event, which allows individual ejecta particles to be tracked along their ballistic trajectories to determine the particles ejection position, speed, and angle. The rtps projects a laser plane vertically onto the target surface to illuminate a cross-section through the growing impact crater, which is then imaged by a video camera. This allows the crater profile to be traced during crater excavation, growth, and modification. Both of these techniques will provide insight into the effects of target topography and heterogeneity on the highly dynamic process of crater excavation, growth, and modification. A 3D laser scanner will be used to determine crater shapes and dimensions with submillimeter precision. Relevance: impact cratering is a major process affecting planetary surfaces at all scales and throughout time in the solar system. The experimental studies of the dependence of impact cratering on target topography and heterogeneity proposed here are relevant to solar system workings in terms of the evolution and modification of surfaces. (appendix c.3).