Many of the small asteroids in the near-earth space (so-called near-earth asteroids or neas) are known to be rubble piles, i.e. composed of a granular material. The understanding of the strength and…

The University of Puerto Rico was awarded a $100,000 cooperative agreement by a civilian federal agency effective October 1, 2021, with completion targeted for September 30, 2026. The contract supports research to characterize how seismic waves travel through granular materials that simulate rubble-pile asteroids under microgravity conditions aboard the International Space Station (ISS). This research addresses a critical gap in understanding near-Earth asteroids (NEAs), which are known to consist of loosely bound rubble piles, and directly supports ongoing NASA missions including OSIRIS-REX and Lucy, as well as planetary defense initiatives. The work focuses on measuring the speed of sound in high-fidelity asteroid simulants under the microgravity environment (approximately 10⁻⁵G) relevant to small asteroids, since sound velocity in granular materials depends on factors including grain composition, size, and confining pressure.

The research has direct applications to multiple scientific objectives: understanding solar system formation, supporting active space missions that collect samples from small bodies, and evaluating impact mitigation strategies. Impact-induced seismic activity on small asteroids causes surface modification processes including particle segregation through the Brazil Nut Effect, crater degradation, and potential particle ejection—phenomena observed during the OSIRIS-REX mission at asteroid Bennu. By characterizing how seismic waves propagate through asteroid materials under realistic gravity conditions, this contract will enhance scientific understanding of asteroid dynamics and inform planetary protection strategies. The award carries no set-aside designation and is located at the University of Puerto Rico's San Juan campus.

Many of the small asteroids in the near-earth space (so-called near-earth asteroids or neas) are known to be rubble piles, i.e. composed of a granular material. The understanding of the strength and dynamics of these rubble piles is strongly linked