On October 4, 2025, NASA’s Perseverance rover did something it was never designed to do. Instead of studying rocks inside Jezero Crater, the six-wheeled geologist tilted its Mastcam-Z camera toward the Martian sky and snapped a long-exposure photograph of comet 3I/ATLAS, a chunk of ice and dust that originated around a distant star and was passing through our solar system on a one-way trip. The resulting image, a faint smudge set against streaking star trails, marks the first time any surface vehicle on another planet has photographed an interstellar object.
The comet was roughly 18.6 million miles (29.9 million kilometers) from Mars at the time, according to NASA’s campaign overview. Perseverance was not working alone. The observation was part of a coordinated, multi-spacecraft effort involving orbiters from both NASA and the European Space Agency, all pointed at the same rare target during its closest approach to the Red Planet.
Only the third interstellar visitor ever detected
Comets and asteroids normally orbit the Sun, bound by its gravity. An interstellar object is different: it travels on a hyperbolic trajectory, meaning it is not gravitationally bound to our star and will never return once it leaves. Before 3I/ATLAS, astronomers had confirmed only two such visitors. The first, 1I/’Oumuamua, was spotted in October 2017 and puzzled scientists with its elongated shape and lack of a visible coma. The second, 2I/Borisov, was discovered in August 2019 by amateur astronomer Gennadiy Borisov and behaved more like a conventional comet, complete with a gas-and-dust tail.
Both earlier objects were observed exclusively from Earth and Earth-orbiting telescopes. 3I/ATLAS changed that. Its trajectory carried it close enough to Mars that spacecraft already stationed at the planet could study it from a completely different vantage point in the solar system, at a different distance and viewing angle than anything achievable from Earth alone.
A coordinated campaign across agencies and altitudes
The effort began two days before Perseverance looked up. On October 2, 2025, NASA’s Mars Reconnaissance Orbiter swung its powerful HiRISE camera away from the Martian surface and aimed it at the comet. Using a 3.2-second exposure from roughly 30 million kilometers away, HiRISE achieved a resolution of about 30 kilometers per pixel, enough to detect the comet’s coma, the diffuse cloud of gas and dust surrounding the nucleus, but not enough to resolve the nucleus itself. The HiRISE instrument team at the University of Arizona noted that jitter smearing during the exposure further limited image quality.
ESA contributed two additional perspectives. Between October 1 and 7, the ExoMars Trace Gas Orbiter trained its CaSSIS camera on 3I/ATLAS, while Mars Express also attempted observations during the same window. The comet’s closest approach to Mars-based spacecraft occurred around October 3 at a distance of approximately 30 million kilometers, according to ESA’s summary.
Then came Perseverance’s turn. On October 4, the rover used Mastcam-Z, a pair of zoomable cameras mounted on its mast, to capture the long-exposure frame that would become the campaign’s most symbolically striking result. The processed image, along with metadata including exposure time, filter selection, and acquisition timestamp, is hosted in NASA’s dedicated 3I/ATLAS image gallery. Raw frames are also available through the rover’s standard image portal, anchored to the mission’s sol count and local mean solar time.
Why observing from Mars matters
Studying a comet from two planets instead of one is not just a novelty. Different viewing geometries let scientists triangulate the structure of a comet’s coma, measure how dust and gas are distributed in three dimensions, and track how activity changes with solar distance and illumination angle. Earth-based telescopes saw 3I/ATLAS from one direction; Mars-based instruments saw it from another, separated by tens of millions of miles. In principle, combining those perspectives could reveal asymmetries in the comet’s outgassing or dust jets that a single vantage point would miss.
A surface observation adds yet another layer. Perseverance sits at the bottom of Mars’s thin atmosphere, looking up through a column of air roughly 100 times less dense than Earth’s. That means less atmospheric distortion, though the rover’s cameras are far less powerful than a dedicated space telescope. The scientific value of the Mastcam-Z image lies less in its resolution than in its geometry: it records the comet’s position from a known point on the Martian surface at a precise time, a data point that can help refine the object’s orbit.
What scientists still do not know
The images are confirmed and publicly archived, but the deeper scientific questions remain open. No spectral analysis or composition data from the Perseverance observation has been released as of June 2026. Mastcam-Z can image through different filters, but extracting detailed composition information from a faint, distant source is technically demanding, and it is unclear whether the data quality supports that kind of analysis.
The HiRISE observation faces its own limits. With the nucleus unresolved at 30 kilometers per pixel and jitter smearing compounding the problem, the comet’s physical size, shape, and surface characteristics remain unknown from that dataset. For an object born around another star, nucleus properties would be among the most scientifically prized measurements, offering clues about how solid bodies form in alien planetary systems and what materials survive the long drift through interstellar space.
ESA has confirmed that Mars Express attempted observations but has not published detailed results or indicated whether usable data was collected. The Trace Gas Orbiter’s CaSSIS images have been referenced in ESA’s public communications, but full scientific analysis has not yet appeared in peer-reviewed literature as of June 2026. Until those datasets are processed, calibrated, and released, the complete scientific yield of the campaign cannot be assessed.
A broader question looms over all of it: how does 3I/ATLAS compare to ‘Oumuamua and Borisov? The first interstellar object showed no coma and defied easy classification. The second looked like a fairly normal comet. Where 3I/ATLAS falls on that spectrum, and what that placement reveals about the diversity of material drifting between stars, depends on analysis that is still underway.
What the raw data already tells us
Even before deeper studies are published, the primary records establish several things firmly. An interstellar comet passed within tens of millions of kilometers of Mars in early October 2025. Multiple spacecraft at and around the planet, including a rover on the surface, successfully imaged it in a planned, coordinated campaign. The resulting data are archived in open repositories maintained by NASA and ESA, documented with timestamps, instrument settings, and known limitations.
The Perseverance photograph, modest as it appears, represents a genuine first. No rover, lander, or surface vehicle on any planet had previously captured an image of an object from another star system. That milestone, combined with the orbital observations from MRO and ESA’s spacecraft, means 3I/ATLAS is already the most thoroughly observed interstellar visitor to date, recorded from two planets and multiple altitudes above one of them. The full scientific story will take months or years to unfold as teams cross-calibrate instruments, merge datasets, and publish peer-reviewed results. But the raw evidence, sitting in publicly accessible archives, is already enough to confirm that something extraordinary was seen from the floor of a Martian crater.
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*This article was researched with the help of AI, with human editors creating the final content.
