Every so often, the universe delivers us a puzzle that sparks both scientific inquiry and wild imagination. In 2025, that puzzle came in the form of an unusual visitor from the depths of interstellar space—a mysterious object named 3I/ATLAS.
At first glance, it behaves like a comet: a body of ice and rock that glows brighter as it approaches the Sun. Yet, for some astronomers, including the outspoken Harvard astrophysicist Avi Loeb, there’s reason to consider a more extraordinary possibility. Could it be something artificial, perhaps even sent deliberately by another civilization?
A Cosmic Visitor Unlike Most
Astronomers first detected 3I/ATLAS hurtling into the solar system earlier this year. It didn’t originate here—it’s an interstellar object, meaning it traveled across the void between stars before wandering into our neighborhood.
So far, humanity has only seen two such objects before this one:
- ʻOumuamua (2017): The first confirmed interstellar visitor. It had an elongated, cigar-like shape, no visible tail, and an odd acceleration that puzzled astronomers.
- 2I/Borisov (2019): More comet-like, with a classic tail and behavior that fit our expectations better.
That makes 3I/ATLAS only the third confirmed interstellar object, placing it in a very small and fascinating category.
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The Comet Explanation
Most scientists agree that 3I/ATLAS is likely just a comet. Observations from the Gemini South telescope in Chile showed it developing a long, glowing tail as it neared the Sun. That tail comes from sublimation—ice on its surface turning directly into gas, carrying dust with it, and leaving behind the spectacular stream we associate with comets.
For astronomers, this is the expected behavior of a cold, icy object entering the warm inner solar system. Nothing too out of the ordinary.
But Loeb isn’t convinced the story is so simple.
Avi Loeb’s Bold Idea
Loeb, who previously stirred controversy by suggesting ʻOumuamua might have been a piece of alien technology, believes we should at least entertain the possibility that 3I/ATLAS isn’t purely natural.
Why? For starters, its size estimate is eye-popping. It could be as large as 28 miles across—making it up to a million times more massive than either ʻOumuamua or Borisov. That’s a staggering jump, and Loeb argues that finding something this massive wandering alone through interstellar space is statistically unlikely.
“It’s not that I claim it must be artificial,” Loeb has said in interviews. “It’s that we shouldn’t dismiss the idea without checking.”
A Path With Precision
What also catches his attention is the object’s trajectory. Instead of taking a random path, 3I/ATLAS is threading its way surprisingly close to several planets: Mars, Venus, and Jupiter among them. At one point, its path will bring it within 1.67 million miles of Mars’ orbit—a distance that, in cosmic terms, is practically a hair’s breadth.
Loeb called this “remarkable fine-tuning.” If you were sending an object into another star system, he argues, passing near multiple planets would be a clever way to gather information.
A Call to Action
With 3I/ATLAS about to make its closest approach to the Sun, Loeb sees a once-in-a-lifetime opportunity. He has called on NASA to redirect some of its spacecraft—like the Mars Reconnaissance Orbiter or Juno, which already operate within the solar system—to keep an eye on the object.
Why? If it does something unusual—say, release smaller objects or probes—we might catch it in the act.
“If we are visited by a technological object like 3I/ATLAS,” Loeb said in one podcast, “it could either visit us or release mini-probes that arrive to Earth and appear as unidentified aerial phenomena.”
It’s a bold statement, blending the worlds of astronomy and UFO research, two fields that don’t often mix comfortably.
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Skeptics Push Back
Unsurprisingly, many scientists are skeptical of Loeb’s theories. For them, natural explanations fit the data just fine.
The size estimate, for example, is not confirmed—it depends heavily on assumptions about how reflective the object is. If it’s darker than expected, it could be smaller. The trajectory, while intriguing, could simply be the result of chance gravitational interactions.
And most importantly, the simplest explanation still holds: a rock covered with ice is passing near the Sun, the ice is evaporating, and the gas and dust are forming a tail. No alien technology required.
Loeb himself acknowledges this possibility. “It may well be just a rock with some ice,” he admitted in one interview. But he insists that brushing off anomalies without investigation is bad science.
The Shadow of ʻOumuamua
Loeb’s willingness to consider alien involvement stems largely from the case of ʻOumuamua, the first interstellar object discovered in 2017.
Unlike Borisov and ATLAS, ʻOumuamua had no visible tail. Instead, it exhibited a strange acceleration as it left the solar system—something that couldn’t be explained by gravity alone. Many scientists suggested sublimation of gases could account for it, even if we didn’t see the gases directly.
Loeb, however, proposed something far more controversial: ʻOumuamua could have been a thin, light-sail-like object—possibly artificial. His ideas drew sharp criticism, but they also sparked debate about how open-minded science should be when confronted with the unknown.
For Loeb, 3I/ATLAS is a chance to revisit that debate with new evidence.
Why Interstellar Objects Matter
Even if 3I/ATLAS turns out to be a perfectly ordinary comet, these interstellar visitors are incredibly valuable for science.
- Cosmic Samples: They bring material from other star systems, offering a glimpse of what exists beyond our neighborhood.
- Clues to Planet Formation: Studying their composition helps scientists understand how solar systems form and evolve.
- Potential for Panspermia: Some theories suggest comets might spread the ingredients for life across galaxies. Interstellar comets could, in theory, carry those ingredients from one system to another.
In other words, every interstellar object is like a postcard from a faraway place.
Keeping an Open Mind
Loeb’s broader point is not that aliens are definitely here, but that scientists shouldn’t be afraid of considering it. In one of his blog posts, he contrasted two mindsets:
- The dogmatist, who tries to force every new observation into familiar categories.
- The open-minded scientist, who welcomes the unexpected, even if it challenges long-held assumptions.
As he put it: “Nature is more imaginative than we are—and it doesn’t care whether we figure it out.”
The Bigger Picture
Whether 3I/ATLAS is just a comet or something stranger, its arrival is a reminder that the universe is far from predictable. For all of our telescopes and theories, surprises still come hurtling out of the dark.
The story of this mysterious traveler also highlights a deeper tension in science: the balance between skepticism and imagination. Skepticism keeps us grounded, protecting us from leaping to wild conclusions without evidence. Imagination, however, pushes us to ask questions that might otherwise go unasked.
In the case of 3I/ATLAS, both instincts are at play. Most scientists lean toward the comet explanation, while Loeb urges us to stay alert to the possibility of something more.
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A Final Thought
For now, the truth about 3I/ATLAS remains uncertain. It will sweep past the Sun, blaze briefly in our skies, and then vanish into the darkness, continuing its journey toward another star.
Will it leave behind only dust, or will it surprise us with something we never expected? Time, and careful observation, will tell.
Either way, this interstellar interloper serves as a cosmic reminder: the universe is full of mysteries, and sometimes the strangest explanations might just be worth considering.
Featured image: Freepik/International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist, CC BY 4.0.
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