Soft Astronomy

Compact mass-spring models can measure remarkably small deformations while conserving angular momentum. We use them within an N-body code to simulate tidal evolution of viscoelastic spinning objects, tying simulated rheology to spin dynamics, orbital drift and the internal distribution of tidally generated heat. Discoveries made using this simulation technique include a resonant mechanism to tilt Pluto and Charon's minor satellites and a way to shut down Bi-YORP effect drift in binary asteroids with spin-synchronous secondaries.

Recent missions have revealed that Near-Earth Object are comprised of rubble. With scaling laws developed for impact craters we relate laboratory experiments of granular systems to processes that take place on rubble asteroids. Laboratory experiments of impacts into polydisperse media show that ejecta tends to leave boulders stranded on the surface. Low velocity impacts are likely to ricochet. Empirical force laws characterizing lift and drag are dependent on substrate particle size. Short compressive flows and landslides can cause boulder alignment.