3I/ATLAS is Now Headed Toward Mars, as Mystery Surrounding Interstellar Visitor Grows

Micah Hanks·
3I/ATLAS
A composite image showing the movement of 3I/ATLAS, as seen by the ESO’s Very Large Telescope (Credit: ESO/O. Hainaut)

Welcome to this edition of The Intelligence Brief… This week, astronomers are preparing for the close approach of the interstellar comet 3I/ATLAS, which will pass near Mars on October 3, 2025, offering scientists their best chance yet to study this mysterious cosmic visitor. In our analysis, we’ll be looking at 1) how NASA’s HiRISE camera aboard the Mars Reconnaissance Orbiter could capture unprecedented images of the comet’s nucleus and dust cloud, 2) why estimates suggest 3I/ATLAS may be nearly seven billion years old, making it the oldest comet ever observed, 3) what clues its carbon-dioxide-rich plume and possible tail could reveal about its composition and origins, and 4) how interstellar objects like 3I/ATLAS may hold insights into the very formation of Earth itself.

Quote of the Week

“This is an object from a part of the Galaxy we’ve never seen up close before.” 

  – Professor Chris Lintott

RECENT NEWS from The Debrief

Mysterious Comet 3I/ATLAS is Bound for Mars: Here’s What We Know

The cosmic drama of 3I/ATLAS, an interstellar object that was first spotted in our solar system in July, continues to unfold as astronomers now say the mysterious visitor is on its way toward Mars.

In the early days of October 2025, 3I/ATLAS will make its closest approach to Mars, passing a little more than 18,019,764 miles from the Red Planet on October 3. This close approach will offer scientists an unprecedented chance to observe the interstellar comet that has had so many in the science community talking since its discovery, with speculations about the object including theories involving extraterrestrial technology.

Although 3I/ATLAS displays several unusual characteristics, currently there have been no obvious signs of technosignatures that could be associated with unknown technologies, and current data points to the space object being a comet, and an unusual one.

Even though it appears to behave most consistently with a known class of celestial objects, there is plenty about the comet’s behavior that has tantalized astronomers in recent days. With its forthcoming approach toward Mars, the mystery of 3I/ATLAS only deepens as astronomers anticipate getting their best look at it to date while it makes its rendezvous with the Red Planet.

A Cosmic Enigma Approaches

Fortunately, as 3I/ATLAS passes Mars, the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter (MRO) will be aimed in its direction, allowing the orbital spacecraft to capture images of the comet as it passes.

This will likely mark an important development in the ongoing saga of 3I/ATLAS, since the camera’s position and capabilities should allow it to obtain images that are sharp enough to distinguish the comet’s nucleus from its surrounding dust cloud, which recent studies have revealed to be very rich in carbon dioxide.

One of the Oldest of Its Kind

Matthew Hopkins, one of the astronomers who first identified 3I/ATLAS, described the discovery as a remarkable surprise due in part to estimates of its extreme age.

According to Hopkins and his team’s Ōtautahi–Oxford model, it’s possible the object may be close to seven billion years old. If so, that would mean it is by far the oldest comet astronomers have ever observed, which might also provide clues about some of the unusual behaviors associated with it.

That isn’t to say 3I/ATLAS’s age is necessarily all that unusual though, since there are likely to be countless comets of similar age drifting around in the universe. In the past, it may also be likely that comets this old—or perhaps even older—made their way through our solar system. However, astronomers weren’t equipped to detect them at that time, making the current opportunity to observe such an ancient interstellar comet an unprecedented first.

Further Clues Expected to Emerge

In the weeks ahead, key indications that will provide context for the comet’s origins will likely begin to emerge in the forthcoming imagery during its near approach.

Among these, astronomers will be eager to see whether the comet begins to produce a luminous tail as it moves closer to the Sun, which will allow some limited opportunities to collect spectral data that may reveal more about the object’s composition. However, at its very closest approach, 3I/ATLAS will be obscured from view by the Sun, at which time the heat it encounters will bake off the greatest amount of material from its surface to date.

Another reason our observations—limited though they are—of 3I/ATLAS are important is that it is possible that in the distant past, interstellar bodies like this could have even been influential in Earth’s formation. Namely, if an ancient interstellar object arrived in our early solar system and became trapped within the Sun’s birth nebula, it could have released materials that eventually coalesced into the planet we call our home today.

Given such possibilities, 3I/ATLAS might not only help astronomers illuminate the history of the Milky Way’s thick disc and the unusual objects that inhabit it; it may also help us understand the deeper cosmic origins of our own world.

That concludes this week’s installment of The Intelligence Brief. You can read past editions of our newsletter at our website, or if you found this installment online, don’t forget to subscribe and get future email editions from us here. Also, if you have a tip or other information you’d like to send along directly to me, you can email me at micah [@] thedebrief [dot] org, or reach me on X: @MicahHanks.

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