--- title: "The Mysterious Object Cruising Toward Mars Is Doing Something Very Peculiar" description: "Interstellar object 3I/ATLAS is sprouting a separate, \"anti-tail,\" as Harvard astronomer Avi Loeb suggests." date: "2025-09-11" modified: "2025-09-11" authors: - name: "Victor Tangermann" job_title: "Senior Editor" link: "https://futurism.com/authors/victor" url: "https://futurism.com/mysterious-object-mars-anti-tail" categories: - "Astronomy" - "Mars" - "Space" tags: - "3i/atlas" - "avi loeb" - "interstellar objects" --- # The Mysterious Object Cruising Toward Mars Is Doing Something Very Peculiar ![Interstellar object 3I/ATLAS is sprouting a separate, "anti-tail," as Harvard astronomer Avi Loeb suggests.]() *\Image: Getty Images\* A mysterious object from interstellar space is screaming through our solar system right now, and is expected to rip past Mars and Jupiter over the coming months before exiting back into the void between stars. Astronomers have been [fascinated by the unusual visitor](), dubbed 3I/ATLAS after its discovery in July, and have broadly come to the conclusion that it's a comet comprised of ice and dust particles. As the object approaches its closest point to our Sun, its activity is steadily picking up as it's believed to be shedding gases and dust, [giving it a growing tail](). And intriguingly, according to images taken by NASA's Hubble Space Telescope, the object isn't just growing one tail — it's also sprouting a separate "anti-tail," pointing in the direction of the Sun, as Harvard astronomer Avi Loeb suggests in a new, [yet-to-be-peer-reviewed paper](). "The anti-tail is an extension of the glow of scattered sunlight around 3I/ATLAS towards the Sun and not away from it — as typically the case for comets," Loeb explained in a new [blog post](). "This anomalous anti-tail, not a result of geometric perspective, had never been reported before for solar system comets." Loeb and fellow Harvard astrophysicist Eric Keto suggest this anti-tail could be the result of ice fragments being shed from 3I/ATLAS' surface instead of "refractory dust particles as previously assumed." This strange new appendage "represents an extension of the snow line, or survival distance of a sublimating ice grain, in the direction of the Sun," Loeb suggests. The researchers determined that while most of 3I/ATLAS' mass is made up of carbon dioxide, the "longest-surviving grains are mostly made of water (H2O) ice, which evaporates more slowly than carbon dioxide." "The ice fragments evaporate after some time but because of the enhanced mass loss in the Sun-facing side, more of the bigger fragments can reach a large distance," Loeb told *Futurism* in an email, "giving rise to an anti-tail namely a glow that is extended towards the Sun." Astronomers examining the object using numerous high-powered space telescopes including NASA's James Webb [previously found]() that the object's coma, or the gas and dust surrounding its nucleus, features a [much higher ratio]() of carbon dioxide to water than expected. The fleeting visitor was also observed [changing color](), from red to a blue-green glow, indicating a "steep rise in the production of cyanide" in the absence of iron, as Loeb suggested in a [previous blog post](). "Natural comets generically show iron and nickel simultaneously, as both elements are produced together in the ejecta of supernova explosions," Loeb wrote in a [blog post last month](). Loeb's most headline-grabbing claims around the object have invoked the possibility that 3I/ATLAS could've been sent to us by an extraterrestrial civilization. But the more data comes in, the more likely it is that we're looking at a comet, not an artifact from an alien species. Still, it's a fascinating visitor — and just the third interstellar object ever detected, after 'Oumuamua in 2017 and 2I/Borisov in 2019. "Altogether, 3I/ATLAS is different from the first interstellar object 1I/'Oumuamua which displayed no signs of gas or dust around it but nevertheless exhibited non-gravitational acceleration," Loeb wrote in his latest blog post. "It is also different from the second interstellar object 2I/Borisov which behaved like a familiar comet." As 3I/ATLAS approaches the Sun, it will [provide an unprecedented opportunity]() to direct distant NASA and European Space Agency space probes to take a closer look. But time is quickly running out, giving scientists very little time to jump into action. **More on 3I/ATLAS:** *[Mysterious Object Headed Into Our Star System Is Now Changing Color]()* ## Author I've been at Futurism since 2017, where my role has evolved to encompass design, writing, and increasingly editing. I've always been fascinated by space exploration and advanced transportation, which I've leaned into by interviewing luminaries in those fields while closely following the dimensions of policy and regulation that allow next-generation projects to succeed -- or, sometimes, to fail. I'm also keenly interested in the effects of generative AI on society, policies, and democratic institutions, as well as clean energy, physics and biology, and the vagaries of tech leadership. My work for Futurism has been cited by publications including Ars Technica, Gizmodo, PC Magazine, Jalopnik, Fox News, and the New York Post. I spent my childhood living in locations including Manila, the Philippines, and Geneva, Switzerland, attended McGill University, and now live in Toronto, Canada. Before Futurism I worked at AskMen and a small photography studio. In my free time, I'm an avid gardener, foodie, and craft beer lover, as well as a maker of artisanal hot pepper sauces. I have a magnificent dog named Freida. ### Author social links [Bluesky]()