NASA's Mars Fleet Captures Unprecedented Views of Interstellar Comet 3I/ATLAS

Credit: NASA/JPL-Caltech

NASA's Mars spacecraft have turned their instruments toward the heavens, capturing extraordinary data on 3I/ATLAS, only the third interstellar object ever discovered passing through our solar system.

In early October, the Mars Reconnaissance Orbiter (MRO) snapped a close-up view, the MAVEN orbiter gathered unique ultraviolet imagery, and the Perseverance rover even caught a faint glimpse from the Martian surface, providing a multi-faceted look at this mysterious visitor.

The observations are a scientific bonanza. The MRO observed the comet from just 19 million miles (30 million kilometers) away, providing one of the closest views any spacecraft or Earth-based telescope will achieve. Using its powerful High Resolution Imaging Science Experiment (HiRISE) camera, which normally scans the Martian landscape, the orbiter captured an image showing the comet as a pixelated white ball.

This ball is actually the coma—a cloud of dust and ice shed by the comet as it travels. “Observations of interstellar objects are still rare enough that we learn something new on every occasion,” said Shane Byrne, HiRISE principal investigator at the University of Arizona. “We’re fortunate that 3I/ATLAS passed this close to Mars.”

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Meanwhile, the MAVEN orbiter provided a completely different but equally critical perspective. Over 10 days starting September 27, its Imaging Ultraviolet Spectrograph (IUVS) camera captured data to determine the comet's chemical makeup.

These ultraviolet images, stated in the mission report, are unique among all observations this year for their ability to measure how much water vapor the comet releases as the Sun warms it. “The images MAVEN captured truly are incredible,” said Shannon Curry, MAVEN’s principal investigator at the University of Colorado Boulder. “The detections we are seeing are significant, and we have only scraped the surface of our analysis.”

The data from MAVEN goes beyond pretty pictures. The IUVS instrument measured the ratio of deuterium to regular hydrogen in the comet, a key tracer that can reveal secrets about its origin and evolution in interstellar space.

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“There was a lot of adrenaline when we saw what we’d captured,” said Justin Deighan, MAVEN’s deputy principal investigator. “Every measurement we make of this comet helps to open up a new understanding of interstellar objects.”

Completing the Martian trifecta, NASA’s Perseverance rover joined the observation campaign from its vantage point in Jezero Crater. On October 4, the rover’s Mastcam-Z camera managed to detect the comet as a faint smudge in the sky.

This was no easy feat; the exposure had to be exceptionally long, and because the camera is fixed, the stars appear as streaks. This faint detection underscores the challenging nature of observing such distant objects.

Together, this coordinated effort by NASA’s Martian fleet turns a fleeting celestial passage into a lasting scientific opportunity. The imagery from HiRISE will help scientists estimate the nucleus size, while MAVEN’s ultraviolet data will unravel the comet's composition.

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As these visitors from deep space remain rare, each piece of data collected by the Mars spacecraft provides a priceless clue to understanding the building blocks of planetary systems far beyond our own.