Planetary Defense Faces a New Reality As Interstellar Objects Like 3I/ATLAS Become More Common

But interstellar objects raise new questions. A deflection strategy designed for a slow-moving, rubble-pile asteroid may not apply to a compact, fast-moving object entering the solar system for the first and only time. Even determining whether deflection is feasible requires rapid characterization—knowing what an object is made of, how it reacts to solar heating, and whether non-gravitational forces are acting on it.

In the case of 3I/ATLAS, astronomers have already detected signs of non-gravitational acceleration, meaning the object’s motion cannot be explained by gravity alone. For planetary defense, that matters. Any mitigation effort must account for forces that could alter an object’s trajectory unpredictably.

There is also a strategic dimension to this conversation. Planetary defense is no longer purely a scientific endeavor; it is increasingly intertwined with global security planning. Detection networks, space-based sensors, and rapid-response missions all rely on shared data and international cooperation. Interstellar objects do not respect national borders, and neither can the systems designed to monitor them.