A new study published in Nature Communications has developed a universal framework to predict the tensile strength of granular asteroids—space rocks made up of loose, rocky material. Researchers have long studied how these bodies stay intact, but earlier models treated the grains as perfect spheres, while in reality, they are angular and irregular. The new study successfully incorporated realistic particle shapes into simulations, offering a more accurate understanding of how these asteroids hold together. The research found that small asteroids, those less than 150 meters (490 feet) in diameter, can spin rapidly with periods shorter than 2.4 hours. However, larger asteroids face a limit known as the "rubble-pile spin barrier." This is due to self-gravity, which becomes more significant as an asteroid grows. If a rubble pile spins too fast, it can break apart. This spin barrier suggests that larger asteroids are indeed rubble piles rather than solid rock. In contrast, smaller asteroids are not constrained by this barrier because their self-gravity is too weak. Instead, cohesive forces between the grains—like the van der Waals forces—can hold them together. In 2010, scientists proposed that van der Waals forces between fine grains could provide the necessary cohesion for small asteroids. These forces act between particles in the regolith, the loose surface layer of an asteroid. In 2014, researchers tested this idea using spherical particles and found that small grains could act as a weak "cement" between larger boulders. However, simulations at the time could not handle realistic particle shapes, and the cohesive forces were assumed rather than measured. That changed with NASA's OSIRIS-REx mission, which returned samples from the asteroid Bennu in 2023, allowing scientists to measure these properties for the first time. To test their framework, the researchers simulated a small section of an asteroid by creating a bridge between two boulders using a matrix of cohesive grains. They used the open-source code LMGC90 to run 78 simulations, varying the shape and size of the grains. Some grains were perfect spheres, while others were polyhedra—shapes ranging from nearly round to highly elongated. The simulations showed that the strength of the bridge depended on both the size and shape of the grains. Smaller grains created stronger bridges because they could fit together more tightly, increasing contact points. Angular grains also provided more contact points and reduced empty spaces between particles, enhancing cohesion. Applying this framework to Bennu, the researchers found that the asteroid's surface strength is below 1 pascal—about 50 times weaker than a small coffee cylinder made from freshly ground beans. This weakness is due to a lack of fine dust, which is needed to fill gaps between larger grains and provide enough cohesive contacts to strengthen the structure. Future research aims to extend this framework to a wider range of grain sizes and to study the interiors of asteroids, which remain unseen by any mission to date. This study provides essential data for simulating asteroid impacts and testing methods to deflect potentially hazardous space rocks.