Exciting new images from High-Resolution Image Science Experiment onboard NASA’s Mars Reconnaissance Orbiter will enable astronomers to refine their estimates regarding the size of 3I/ATLAS, the third known interstellar object that has passed through our solar system.
This image of 3I/ATLAS was captured by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter on October 2, 2025. Credit: NASA / JPL-Caltech / University of Arizona.
On October 2, 2025, the Mars Reconnaissance Orbiter (MRO) observed 3I/ATLAS from approximately 30 million km (19 million miles) away.
The MRO team utilized the High-Resolution Imaging Science Experiment (HiRISE), which typically focuses on the Martian surface.
By maneuvering, the spacecraft can direct its camera toward other celestial objects. This method was previously employed in 2014 when HiRISE collaborated with MAVEN to examine the comet Siding Spring.
“Observations of interstellar objects are still infrequent, so each time we learn something new,” noted Dr. Shane Byrne, HiRISE principal investigator and researcher at the University of Arizona.
“We were fortunate that 3I/ATLAS came close to Mars.”
Captured at a resolution of about 30 km (19 miles) per pixel, 3I/ATLAS appears as a pixelated white sphere in the HiRISE images.
“This sphere is a cloud of dust and ice, referred to as a coma, that the comet emits as it travels past Mars,” the researchers added.
Further analysis of HiRISE images could assist scientists in establishing an upper limit on the size of a comet’s core, composed of ice and dust.
The images might also uncover properties of particles known as comas within the comet’s atmosphere.
Ongoing scrutiny of the images may reveal nuclear fragments and gas jets expelled as comets disintegrate over time.
“One of MRO’s greatest contributions to NASA’s Mars research is its ability to observe surface phenomena that only HiRISE can detect,” explained Dr. Leslie Tampali, MRO’s project scientist and a research scientist at NASA’s Jet Propulsion Laboratory.
“This opportunity allows us to study passing space objects.”
“Thanks to NASA’s versatile fleet of spacecraft throughout our solar system, we can continue to observe this dynamic entity from unique perspectives,” stated Georgia Tech researcher Professor James Ray, a HiRISE co-investigator.
“All three prior interstellar objects exhibit significant differences from one another and from typical Solar System comets, making every new observation incredibly valuable.”
“Being able to observe a visitor from another star system is extraordinary in itself,” remarked Dr. Tomás Díaz de la Rubia, senior vice president for research and partnerships at the University of Arizona.
“Doing so from a University of Arizona-led instrument orbiting Mars adds to its remarkable nature.”
“This moment highlights the ingenuity of our scientists and the lasting impact of this university’s leadership in space exploration.”
“HiRISE exemplifies how discovery tools can benefit both science and the public interest.”
Source: www.sci.news
