Judging an Airless Body by it's Cover - How Surface Features Can Reveal the History of Changes on and Beneath the Surface of an Airless Body

Our understanding of the surfaces of airless planetary surfaces come predominantly from remote sensing observations of the uppermost layers, which record a history of change due to internal and external forces. One key to interpreting this data is extensive laboratory investigations of regolith behavior, using experiments both in ground-based and microgravity environments. I will discuss some of the key observed properties of regolith on airless planetary bodies, as well as what that surface may tell us about the underlying structure of the body. We have recently performed experiments that are aimed at understanding these surface features, how their causes and effects might vary from those seen on earth, and how we can use surface features to interpret subsurface structure and modifications. One experiment, Strata-1, realized a long-duration microgravity environment by flying aboard the International Space Station for approximately one year. With that experiment, we observe changes in surface layering as a function of changes in dominant gravity vectors and the varied vibration environment. I will also discuss initial results from the SLOPE experiment, which was operated on parabolic airplane flights in order to study how angle of repose changes as a function of particle type and gravity level. We observe distinct differences between the behavior of spherical particles, which are often used in simulations for efficiency, and several types of regolith simulant particles.