U.S. Lacks Defenses Against ‘City-Killer’ Asteroids, Officials Warn

Senior space and defense figures say the United States does not yet possess a reliable way to stop a large asteroid on a collision course with a major city, a vulnerability that has prompted renewed calls for investment in detection, deflection research and emergency planning. The warning underscores that while tracking systems have improved, the capability to alter the path of a truly catastrophic asteroid remains limited.

Stronger detection, but critical gaps remain

In recent public briefings and internal discussions, space officials have underscored that current telescopes and survey networks are much better at finding near‑Earth objects than they were a decade ago. Smaller objects that would burn up in the atmosphere are routinely cataloged, and lead times for many potential impacts have increased. Still, detection capability is not perfect. Some threats can arrive with only months or even weeks of warning, and dark or fast‑moving asteroids remain difficult to spot.

Those shortened lead times matter. Even when an approaching object is identified, the size, composition and rotation of the body affect how it would react to any attempted deflection. For an asteroid large enough to flatten a city, the margin for error is small: determining trajectory and physical properties quickly and accurately is essential to any successful mitigation effort).

Deflection tech exists in theory but not at needed scale

Experts point out that while concept missions and tests have proven certain techniques can nudge an asteroid’s course, those demonstrations do not yet translate into a robust operational capability to stop a truly large, hazardous impactor on short notice. Options under study include kinetic impactors to alter velocity, gravity tractors that use spacecraft mass to tug an asteroid slowly, and more speculative concepts involving explosives or focused energy.

Each approach carries limits. Kinetic impactors require sufficient lead time and precise targeting to change an asteroid’s orbit meaningfully. Gravity tractors need prolonged proximity and are impractical for last‑minute threats. Explosive options are uncertain because they can fragment an object into many dangerous pieces. Officials emphasize that, at present, no single method offers a guaranteed fix for a large, city‑threatening asteroid discovered with limited warning.

What needs to happen next

Policy makers and program managers are being urged to accelerate three priorities: expand search capabilities to catch more objects earlier, fund technology development to scale up verified deflection methods, and create clearer contingency plans for civil authorities. Building an operational deflection system will require engineering prototypes, realistic multi‑agency exercises, international coordination and long‑term financing commitments.

Emergency planning is equally crucial. If an impact is projected with some lead time, communities will need robust evacuation plans, communication systems, and strategies for mitigating fallout and secondary hazards. Experts say that preparing for lower‑probability, high‑consequence events should be treated as part of national resilience planning, not as an afterthought.

For now, the central message from the space community is sobering: while humanity’s ability to catalog near‑Earth objects has improved, the tools to prevent devastating strikes on short notice are still works in progress. Officials stress that closing that gap will require sustained attention and investment if the nation is to move from demonstration projects to dependable planetary defense.