Last July, a NASA telescope located in Chile detected a celestial body ranging between 20 and 30 kilometers in diameter. Named 3I/ATLAS, it was swiftly classified as an interstellar visitor, exhibiting the typical activity of a comet with an icy nucleus surrounded by a cloud of gas and dust, and no indications of artificial technology. Its trajectory was charted, with estimates suggesting it would reach its closest point to the Sun, known as perihelion, before October 30, 2025. Following this closest approach, the comet began its journey away from our solar system, hurtling through space at a formidable speed of approximately 210,000 kilometers per hour.
As only the third object originating from outside our solar system to be discovered, 3I/ATLAS quickly sparked considerable public discussion. Speculation mounted regarding its potential impact on Earth, a common fear when such large, fast-moving celestial bodies are identified. However, the National Aeronautics and Space Administration (NASA) consistently maintained a clear message: 3I/ATLAS never posed a threat to our planet. At its closest point to the sun, the comet was still an immense 210 million kilometers away from our star. While it was observable through terrestrial telescopes until late September, its proximity to the Sun subsequently rendered it impossible to see, though it is expected to become visible again with telescopes in early December.
The very mention of a potential cosmic threat, even a hypothetical one, often leads to questions about planetary defense. In the wake of 3I/ATLAS’s discovery, a new rumor began to circulate: that NASA had activated its planetary defense protocol. This raises a fundamental question about what these protocols actually entail and who is responsible for their initiation. Planetary defense refers to a suite of strategies and measures designed to safeguard Earth from hazards originating in space, such as comets, asteroids, or other celestial objects. It is not a single, monolithic protocol, but rather a coordinated effort involving various international entities, including NASA, the European Space Agency (ESA), and the International Asteroid Warning Network (IAWN).
These organizations maintain a vigilant watch over the cosmos. The ESA, for instance, had knowledge of over 1.2 million asteroids within our solar system by November 2024. Of these, 36,000 are categorized as Near-Earth Objects (NEOs), and approximately 1,700 are included on its risk list, necessitating thorough and continuous monitoring. The ESA’s Planetary Defense Office operates across three key areas: observation, data provision, and risk mitigation. The latter focuses specifically on potentially hazardous asteroids, working through the United Nations’ Space Mission Planning Advisory Group (SMPAG), which coordinates Earth’s collective response to possible impacts.
Beyond observation and data, tangible defense efforts are underway. In October 2024, the ESA launched ‘Hera,’ its inaugural planetary defense mission. Hera is designed to reach the Didymos binary asteroid system by autumn 2026. Its primary objective is to conduct a detailed study aimed at measuring the efficacy of asteroid deflection technology, a critical component in protecting Earth from future impacts. This ambitious project represents a large-scale experiment into what the ESA describes as a “well-understood and replicable planetary defense technique.” Similarly, NASA operates its own Planetary Defense Coordination Office (PDCO), dedicated to locating, tracking, and understanding comets and asteroids that could pose a risk to Earth. The IAWN, a global collaboration of astronomers recommended by a UN resolution and working closely with NASA’s SMPAG, provides recommendations for an international response to the threat of NEO impacts. NASA directly coordinates this network.
Despite the speculation, the reality surrounding Comet 3I/ATLAS and its relation to planetary defense protocols is far more routine than dramatic. No emergency protocol was activated by NASA or any other agency. Instead, what transpired was the launch of a comet observation campaign by the IAWN, under NASA’s coordination. This initiative was designed to refine the precise localization methods for 3I/ATLAS. Days before the comet’s perihelion, the IAWN highlighted that 3I/ATLAS presented a “great opportunity for the community to conduct an observation exercise,” citing its prolonged visibility from Earth and the significant scientific interest it generated. The message was clear and consistent: Comet 3I/ATLAS posed no threat whatsoever.
This observation campaign, which commenced on November 27 and is slated to continue until January 27, serves a specific scientific purpose: to test and improve our ability to accurately measure the positions of comets. Therefore, no planetary defense protocol was initiated due to the presence of 3I/ATLAS near, and now moving away from, our solar system. The IAWN views this exercise as a guide for comet observation, rather than an urgent call to activate any interplanetary defense measures. It underscores the ongoing, meticulous work of planetary defense agencies, a commitment to understanding our cosmic neighborhood that often proceeds quietly, far from public alarm.