In a move that’s sent ripples through the scientific community and conspiracy circles alike, NASA’s Planetary Defense Coordination Office has mobilized the International Asteroid Warning Network (IAWN) to track a colossal interstellar comet dubbed 3I/ATLAS, which measures roughly the size of Manhattan and exhibits behaviors that have astronomers scratching their heads – and one Harvard professor floating the wild theory of extraterrestrial origins. First spotted on July 1, 2025, by NASA’s ATLAS telescope system in Chile, the object – estimated at up to 3.5 miles (5.6 kilometers) in diameter – is barreling through our solar system at speeds defying typical cometary norms, prompting a global “comet campaign” set to run from November 27, 2025, through January 27, 2026. While officials stress there’s no immediate collision risk, the comet’s odd trajectory and emissions have ignited speculation about whether it’s a natural wanderer or something engineered from beyond our stars.

The saga of 3I/ATLAS began innocuously enough in the predawn hours of July 1, when the Asteroid Terrestrial-impact Last Alert System (ATLAS) – a pair of telescopes in Hawaii and Chile designed to hunt for near-Earth threats – flagged an anomalous blip hurtling from the direction of the constellation Lyra. Initial observations pegged it as the third confirmed interstellar object to visit our solar system, following the enigmatic ‘Oumuamua in 2017 and 2I/Borisov in 2019. Unlike those, however, 3I/ATLAS quickly revealed quirks that set it apart. Hubble Space Telescope images from July 21 captured a glowing, green-hued nucleus shrouded in a diffuse coma, with an estimated diameter between 1,444 feet (440 meters) and 3.5 miles – roughly equivalent to Manhattan’s 23 square miles if stretched into a cosmic oblong. By August 20, refined measurements confirmed its outsized scale, making it one of the largest visitors of its kind.

What truly raised eyebrows was its behavior. As it swung perilously close to Venus on August 15, Mars on October 3, and Jupiter later this month, the comet displayed non-gravitational acceleration – a subtle deviation from predicted orbital paths that suggests outgassing or, more intriguingly, propulsion. Probes near Mars relayed images of a cylindrical silhouette coated in what appeared to be nickel plating, glowing an eerie emerald under solar illumination – a material more akin to spacecraft heat shields than icy cometary crust. Adding to the enigma, spectral analysis detected plumes ejecting nickel tetracarbonyl at four grams per second, an alloy absent in natural comets but commonplace in human rocketry for exhaust protection. Perhaps most bizarre: an “anti-tail” – a rare jet of particles streaming toward the sun rather than trailing away, defying the solar wind’s push.

Enter Harvard astrophysicist Dr. Avi Loeb, whose 2021 book “Extraterrestrial” already courted controversy by positing ‘Oumuamua as potential alien tech. In a preprint paper submitted to arXiv on October 15, 2025, Loeb and his team argued that 3I/ATLAS’s trajectory – a hyperbolic arc slingshotting past inner planets in a pattern too precise for randomness – could indicate “intelligent reconnaissance.” “The object’s composition, dominated by carbon dioxide with nickel anomalies, and its anomalous acceleration mirror engineered probes more than primordial ice,” Loeb told The New York Post, refusing to rule out hostile intent. Social media erupted: #AlienComet trended with over 500,000 posts on X by October 22, blending memes of green-glowing UFOs with doomsday preppers stocking bunkers. One viral thread quipped, “If it’s phoning home, Earth’s about to get the worst Yelp review ever.”

NASA, ever the voice of measured calm, downplayed the extraterrestrial angle while activating defenses. On October 22, the agency announced IAWN – a UN-endorsed consortium including the European Space Agency, Japan’s JAXA, and China’s CNSA – would spearhead a tracking drill, not a literal “probe launch” but a coordinated observational push using ground telescopes, the James Webb Space Telescope, and NASA’s upcoming NEO Surveyor infrared observatory, slated for 2028. “This is routine planetary defense,” NASA’s Planetary Defense Officer Lindley Johnson stated in a presser. “3I/ATLAS poses no impact threat – its perihelion is October 30 at 0.8 AU, safely outside Earth’s orbit – but its interstellar nature offers a unique study window.” The campaign aims to refine ephemeris data, potentially spotting surface features or subsurface anomalies via radar from Goldstone Deep Space Network.

Yet, the timing couldn’t be more charged. NASA’s DART mission in 2022 proved kinetic impactors can nudge asteroids like Dimorphos off course, shortening its orbit by 32 minutes – a blueprint for deflection if needed. With budget hawks eyeing planetary defense funding post-2027, skeptics wonder if 3I/ATLAS is a convenient catalyst. “Activating IAWN now, amid government shutdown whispers, smells like a funding ploy,” tweeted one X user, echoing broader debates on NASA’s $25 billion annual tab. Loeb, undeterred, called for a flyby mission akin to ESA’s 2029 Comet Interceptor, tweeting: “If it’s tech, we need eyes on it yesterday.”

Complicating matters: 3I/ATLAS’s path may intersect NASA’s Europa Clipper, launched October 14, 2025, en route to Jupiter’s icy moon. On October 30, the probe could graze the comet’s ion tail, potentially sampling charged particles for isotopic clues – a serendipitous bonus if the spacecraft’s instruments are primed. “Europa Clipper’s magnetometer might detect electromagnetic signatures inconsistent with natural comets,” project scientist Robert Pappalardo told Space.com. Early data from October 21 showed faint particle showers, but confirmation awaits perihelion.

Public fascination peaked during a September 15 lunar eclipse, when 3I/ATLAS glowed vividly against the blood moon, captured in amateur photos going viral with 10 million views. Stargazers from Chile to Hawaii reported it as a “ghostly emerald streak,” fueling Reddit threads like r/STEW_ScTecEngWorld, where users debated: comet or craft? “Loeb’s onto something – the anti-tail screams artificial thrust,” one post read, amassing 5,000 upvotes.

Critics, including Caltech’s Mike Brown, dismissed the hype: “Interstellar objects are weird by definition – Loeb’s alien bias clouds the science.” NASA’s strategy, outlined in its 2023 Planetary Defense Report, prioritizes detection over deflection for objects under 1 km – 3I/ATLAS dwarfs that, but its velocity (up to 50 km/s) complicates modeling. A 1-km impactor could unleash dinosaur-killer energy, but odds here are nil; the real value lies in data for future threats, like the 2029 Apophis flyby.

As telescopes swivel skyward, 3I/ATLAS reminds us of our cosmic vulnerability – and ingenuity. Whether frozen relic or rogue artifact, it’s a wake-up call: in the vast dark, we’re not alone in wondering what’s out there. For now, NASA watches, world agog, as the green ghost glides on.