The HiRISE orbiter successfully photographed interstellar comet 3I/Atlas during its high-speed journey past the red planet, offering scientists their closest view yet
A camera designed to study the dusty Martian landscape has accomplished something far beyond its original mission by capturing images of only the third known interstellar object ever detected passing through our solar system. NASA's HiRISE camera aboard the Mars Reconnaissance Orbiter photographed the interstellar comet 3I/Atlas on Oct. 2 as it raced past the red planet at an astonishing 130,000 miles per hour.
The successful imaging represents a remarkable technical achievement for the HiRISE team. Capturing a comet traveling at such extreme velocity required precise calculations and careful planning to avoid multiple potential obstacles. The team had to account for Mars' thin but problematic atmosphere, which could blur or contaminate the images. They also needed to prevent stray light reflecting off the planet's surface from interfering with the photograph.
Adding to the complexity, the imaging team had to plan their shot to avoid bright background stars that could overwhelm the relatively faint light coming from the distant comet. Despite these challenges, the camera successfully captured the speeding object as it passed approximately 19 million miles from Mars.
Ingrid Daubar, an associate research professor at Brown University and deputy principal investigator for the High-Resolution Imaging Science Experiment, expressed pride in what the veteran instrument continues to accomplish. For nearly two decades, HiRISE has been studying the Martian surface with unprecedented detail, but its capabilities extend far beyond that primary mission.
The camera's talented engineering team has demonstrated an ability to point the instrument away from Mars and accurately target other celestial bodies. This versatility has allowed HiRISE to contribute to scientific research in ways its designers never anticipated when the mission launched.
The velocity at which 3I/Atlas travels through space makes it the fastest object ever observed within our solar system. This incredible speed, combined with its interstellar origin, makes the comet a subject of intense scientific interest. While powerful Earth-based telescopes including the Hubble Space Telescope and James Webb Space Telescope have already photographed the comet, the Mars flyby offered researchers their closest viewing opportunity.
When photographing the Martian surface, HiRISE achieves an impressive resolution of about nine inches per pixel, sharp enough to distinguish individual boulders, rockslides and dust devils on the planet's dynamic terrain. The distance between Mars and 3I/Atlas during the October encounter resulted in a coarser resolution of approximately 19 miles per pixel for the comet images.
Sam Birch, an assistant professor of Earth, environmental and planetary sciences at Brown University who specializes in comet research, believes this resolution still provides valuable scientific data. The images may reveal important details about the comet's size and potentially capture features within its coma, the cloud of ice and dust particles surrounding the comet's solid nucleus.
As 3I/Atlas continues its journey and heats up from solar radiation, material will stream off its surface in jets directed toward the sun. The HiRISE images might capture these sunward jets or other features in the area immediately surrounding the nucleus, providing insights into how interstellar comets behave as they pass through our solar system.
The timing of the Mars flyby offers another scientific opportunity. Scientists understand that comets spin faster as they approach the sun, and 3I/Atlas is scheduled to make its closest solar approach later this month. If the HiRISE team successfully captured the comet's rotation rate in October, researchers could compare that data with rotation measurements taken after the solar encounter, revealing how the sun's influence affects interstellar objects.
While 3I/Atlas holds the distinction of being only the third confirmed interstellar object detected in our solar system, scientists believe such visitors pass through far more frequently than current detection rates suggest. The recently activated Vera C. Rubin Observatory will conduct the Legacy Survey of Space and Time, a comprehensive 10-year scan of the southern sky expected to identify many more interstellar travelers.
Birch views the current investigation of 3I/Atlas as valuable preparation for the wealth of interstellar science that lies ahead as detection capabilities improve.
The comet observation adds another achievement to HiRISE's already impressive scientific record. Daubar noted how the mission has fundamentally changed our understanding of Mars over the past 19 years. Scientists once viewed the red planet as a cold, lifeless world, but HiRISE's continuous monitoring has revealed a far more dynamic environment.
The camera has tracked seasonal changes, documented shifts in the polar ice caps over time, and provided crucial data about active geological processes on Mars. These observations have enhanced scientific understanding of how the Martian climate evolves and how the planet's surface interacts with its thin atmosphere.
Originally designed for a two-year mission, HiRISE has operated for nearly a decade beyond its planned lifespan. Daubar suggests that many of the mission's most significant scientific contributions have emerged during this extended operational period, when the camera has had time to observe long-term changes and take on unexpected challenges like photographing interstellar comets.