Science Seminars

Rotational Evolution of Small Granular Asteroids and the source of their Strength

Speaker: Paul Sánchez (CCAR, CU Boulder)
Date: Thursday, May 16, 2019
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

By now it has been accepted that most of the small asteroids in the Solar System are granular aggregates kept together by gravitational and possibly, cohesive forces. These aggregates can form, deform and disrupt over millennia subjected to different internal and external factors that would ultimately determine how they evolve over time. Parameters such as porosity, cohesive and tensile strength, angles of friction, particle size distributions, stress states and heterogeneity among others, determine how these bodies will react when subjected to different, changing, external factors. These external factors include solar photon momentum, gravitational tides, micro- and macro-impacts and are believed to have produced and shaped the current asteroid population.  In short, it is a competition between the internal strength of the asteroid and the external factors that try to break it apart and this is what we want to understand.

In our research we use a combination of Soil Mechanics theory, Soft-Sphere Discrete Element Method (SSDEM) Simulations and Orbital Mechanics in order to understand how simulated, homogeneous and heterogeneous, ellipsoidal and spherical gravitational aggregates, a crude but useful representation of an asteroid, evolve when rotated to the point of disruption.  Then, we compare our results to the shapes of observed asteroids as well as to the disruption patterns of a few active asteroids.  Our results lead us to believe that the different shapes of observed asteroids as well as their unique disruption patterns could give us clues about their internal structure, strength and geophysical properties in general. In this talk, I will also touch on why the dynamics of granular matter in micro-gravity conditions is important for recent space missions.