Two Kilometer-Scale Asteroids Exceed Spin Barrier, Implying Unexpected Cohesive Strength

Light-curve data from the ATLAS survey and follow-up photometry at the University of Hawaii revealed the rapid spins through repeated brightness variations over multiple nights. Shape modeling and density estimates around 2 g cm^{-3} indicate these bodies should disrupt without internal cohesion exceeding 50–200 Pa, challenging the assumption that most asteroids larger than a few hundred meters are loose aggregates held only by gravity. This aligns with earlier detections of smaller fast rotators but extends the anomaly to objects previously thought stable.

Prior surveys such as the 2019 LCDB compilation and the 2021 study of 2010 JL88 in Nature Astronomy documented similar outliers below 300 m, often attributed to monolithic fragments. The new finds suggest either unrecognized YORP torque acceleration or widespread low-level van der Waals forces throughout the main belt, with implications for deflection strategies in planetary defense scenarios.

Next steps include radar imaging during future close approaches and thermal-infrared observations to constrain surface properties and confirm whether these objects share the S-type composition common among fast spinners.