NASA’s Mars Reconnaissance Orbiter (MRO) has provided unprecedented close-up images of interstellar comet 3I/ATLAS, a rare visitor from outside our solar system. Captured on October 2, 2025, from a distance of 30 million kilometers (19 million miles), these images will help astronomers refine estimates of the comet’s size and composition.
A Unique Opportunity
Interstellar objects—those originating from beyond our sun’s orbit—are exceedingly rare. Only three have been confirmed to pass through the solar system, making each encounter a significant scientific event. The fact that MRO was positioned to observe 3I/ATLAS at such close range is considered fortunate by researchers, as it provides a level of detail not previously possible.
“Observations of interstellar objects are still rare enough that we learn something new on every occasion,” noted Dr. Shane Byrne, HiRISE principal investigator at the University of Arizona. This highlights the value of such encounters for expanding our understanding of planetary systems beyond our own.
How the Images Were Taken
The images were captured using the High Resolution Imaging Science Experiment (HiRISE) camera, typically focused on the Martian surface. However, MRO can rotate to observe celestial objects, a technique previously used in 2014 to study comet Siding Spring. The resulting images show 3I/ATLAS as a pixelated, white ball, representing the comet’s coma—a cloud of dust and ice shed as it travels.
At a scale of roughly 30 kilometers (19 miles) per pixel, the images are detailed enough to potentially reveal the comet’s nucleus size and the properties of its surrounding atmosphere. Scientists are looking for fragments of the nucleus or jets of gas, which can indicate the comet’s breakdown over time.
Implications for Future Research
The HiRISE images could help scientists place an upper limit on the size of the comet’s central core, composed of ice and dust. This is crucial because the properties of interstellar objects can differ significantly from those found within our solar system.
“All three interstellar objects to date have shown striking differences from each other and from typical solar system comets, so every new observation we make is precious,” explained Professor James Wray, a HiRISE co-investigator at the Georgia Institute of Technology. This suggests that the composition and origin of these objects vary widely, making each observation a valuable addition to our knowledge base.
A Testament to Space Exploration
The mission highlights NASA’s ability to leverage its fleet of spacecraft across the inner solar system to study dynamic objects from unique vantage points. The University of Arizona’s leadership in space exploration, coupled with the ingenuity of its scientists, made this observation possible.
“To capture a glimpse of a visitor from another star system is extraordinary in itself,” said Dr. Tomás Díaz de la Rubia, senior vice president for research and partnerships at the University of Arizona. “To do so from a University of Arizona-led instrument orbiting Mars makes it even more remarkable.”
The images captured by MRO represent a significant step forward in our ability to study interstellar objects and provide valuable insights into the broader universe.
