As detection accelerates and our dependence on space-based infrastructure deepens, planetary defense must evolve from a focus on rare catastrophes to managing frequent, decision-relevant risks across the Earth–Moon system.
For decades, planetary defense centered on extremely large, rare asteroids — the so-called "dinosaur killers." While important, these events are statistically infrequent. Today, far more common decameter-scale objects — tens of meters in size — can produce meaningful consequences within human planning horizons. At the same time, modern economies rely heavily on space-based infrastructure: communications, navigation, financial timing systems, climate monitoring, and national security assets all depend on maintaining a safe and usable orbital environment. Planetary defense is no longer only about preventing extinction-level events. It is about safeguarding the stability of an increasingly space-dependent world.
The Rubin Observatory will significantly increase the discovery rate of small near-Earth objects. NASA's NEO Surveyor mission will improve systematic infrared size estimates. ESA's Hera mission is refining our understanding of deflection technologies. Yet detection is advancing faster than decision-grade refinement. Newly discovered objects require rapid orbit refinement, physical characterization, and probability assessment. Without timely follow-up, uncertainty can persist for years — narrowing mitigation options and complicating decision-making. Recent JWST observations of asteroid 2024 YR4 illustrate this shift. Infrared measurements today may effectively buy up to two years of clarity compared to waiting for its next favorable apparition — expanding the space of feasible responses.
For smaller impactors, the issue is not global extinction but systemic disruption. Even a lunar impact — while posing no direct threat to life — raises questions about debris injection and the resilience of orbital infrastructure. Satellite systems cannot simply be rebuilt overnight; the orbital environment is shared and difficult to reset. As humanity expands its presence into cislunar space, planetary defense must account for infrastructure resilience as well as terrestrial safety.
We are at a pivotal moment: detection capabilities are improving rapidly, characterization tools are advancing, and deflection technologies are being tested. Integrating these developments into a scalable, policy-relevant framework now will determine whether planetary defense becomes proactive and economically rational — or remains reactive. The Earth–Moon system is our immediate cosmic neighborhood. Understanding and protecting it is foundational to modern society.