The recent flyby of an interstellar object named 3I/ATLAS has reignited profound questions about humanity's place in the cosmos and our ability to protect ourselves from potential threats from beyond our solar system. While confirmed to be a harmless comet, its passage has prompted leading scientists to issue stark warnings about our planetary defence capabilities.
A Cosmic Visitor Sparks Existential Questions
On December 19, 2025, Earth received a celestial greeting from 3I/ATLAS, a comet composed of rock, dust, and ice that originated from outside our solar system. First detected in July of that year, its arrival captivated scientists, amateur astronomers, and even celebrities. However, for Professor Abraham ‘Avi’ Loeb, the former chair of Harvard University's astronomy department, it represented something more: a test case for how we would respond to an alien visitor.
Loeb, who has spent considerable time analysing the object, points to its chemical composition, trajectory, and size as factors that, while natural, prompt consideration of artificial origins. “In the first case, humanity need not do anything but await the arrival of this interstellar messenger with open arms,” Loeb told Metro. “It is the second option which is of great concern.” Public anxiety is palpable; online searches for ‘planetary defence’ surged by 298% in the three months leading up to the comet's closest approach, with 147,000 queries in a single week during October.
Are We Prepared for a Hostile Encounter?
NASA has been quick to reassure the public. Acting Administrator Sean Duffy stated on social media that 3I/ATLAS is the third interstellar object observed in our system and poses no threat, passing no closer than 170 million miles from Earth. Yet, Loeb argues the mere possibility of an artificial object underscores a critical vulnerability. He believes humanity has already announced its presence through endeavours like the Voyager probes, launched in 1977 with their golden records of Earth's sounds and greetings.
“We should be ready for the possibility of a visitor that detected them,” Loeb cautions. “It may come to save us or destroy us. We’d better be ready for both options.” His proposed solution is an international alien alert system, modelled on the Richter scale for earthquakes. A natural comet would register as zero, while a confirmed alien spacecraft would trigger the maximum alert level of ten.
The Stark Reality of Planetary Defence
If a genuine threat emerged, how would we respond? Science journalist and author Dr Robin Andrews explains that for asteroids, strategies like kinetic impactors (ramming them with a probe) or nuclear devices are theoretically possible, albeit requiring about a decade of advance warning. However, comets like 3I/ATLAS—which reached speeds of 42 miles per second—present a “nightmarish scenario.” Their immense size and velocity would likely render our deflection efforts futile.
The challenge against a hypothetical alien craft is even more daunting. Professor Loeb notes our fastest chemical rockets would “barely bridge the gap” to intercept an object moving at such velocities. While Earth's atmosphere itself acts as a natural defence, superheating incoming objects into plasma, our technological arsenal might be hopelessly outmatched. “The simple fact that the aliens managed to get to Earth in the first place shows they’re more technologically advanced than us,” Dr Andrews concedes.
UFO researcher Mark Christopher Lee offers a bleakly humorous perspective, suggesting our best hope might be a ‘War of the Worlds’-style outcome where alien biology succumbs to Earth's microbes, or that we could “distract them a bit by introducing them to TikTok.”
The passage of 3I/ATLAS has served as a cosmic wake-up call. It highlights the urgent need for global cooperation in monitoring interstellar objects and developing coherent defence protocols. As Professor Loeb starkly concludes, “Since aliens might not respect the way we split territories on Earth among nations, all humans must cooperate in response to existential threats from space.” The comet may have passed harmlessly by, but the questions it raised are only just beginning to orbit.
