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

In simple terms, humanity is about to realize that objects from other star systems will start to pass through our cosmic backyard far more often than previously believed.

That realization carries planetary defense implications that extend beyond impact risk alone. Objects like 3I/ATLAS are not just fast; they can be physically unfamiliar. The persistent sunward emission observed in 3I/ATLAS, for example, challenges standard comet models and complicates efforts to quickly assess mass, composition, and response to solar forces. For defense planners, uncertainty is the enemy of preparedness.

NASA’s Planetary Defense Coordination Office and its international partners have already taken important steps. Missions such as DART, which successfully altered the orbit of the asteroid moonlet Dimorphos in 2022, demonstrated that kinetic deflection is possible. The European Space Agency’s Hera mission, scheduled to rendezvous with the Didymos system in 2026, will turn that experiment into a well-characterized, repeatable defense technique.