NASA’s Perseverance rover captured the Martian moon Phobos crossing in front of the Sun on August 12, 2026, marking the latest in a series of detailed solar transits used by scientists to measure the lumpy moon’s changing orbit and the interior structure of the Red Planet.
The Perseverance Mars rover used its Mastcam-Z camera system to record a fresh transit video of Phobos sweeping across the solar disk from Jezero Crater. The observation, captured on the 1,948th Martian day of the mission, showcases the potato-shaped moon as it slides in front of the Sun. Members of the rover team noted that the resulting animation was tinted to simulate what a human observer on the Martian surface would see through protective solar eclipse glasses.
Orbital Mechanics and the Martian Sky
Phobos is the larger and innermost of the two Martian moons, discovered by American astronomer Asaph Hall on August 17, 1877. Measuring approximately 26 by 22 by 18 kilometers, the satellite orbits about 6,000 kilometers from the surface of Mars, completing a full loop in just 7 hours and 39 minutes. Because its orbital period is roughly three times faster than the rotation of the Red Planet, Phobos rises in the west and sets in the east.
Unlike Earth’s Moon, Phobos is too small and orbits too close to fully block the Sun, meaning any eclipse from the Martian surface is a partial transit rather than a total blocking of solar rays. Past rovers have documented similar events: Spirit and Opportunity made the initial observations in 2004, while Curiosity recorded the first video in 2019. Perseverance itself has captured several such transits since touching down in Jezero Crater in February 2021, including an observation on September 30, 2024, and another on February 8, 2024.
Measuring Martian Tides and a Doomed Orbit
These repeated recordings serve a vital scientific purpose beyond visual documentation. By comparing the various transit recordings, researchers can track subtle shifts in the moon’s orbit over time. The tidal forces exerted by Phobos tug on the deep interior crust and mantle of Mars. Studying how much the moon’s orbit shifts reveals how resistant the Martian crust and mantle are, offering clues about their material composition.
“Each time these eclipses are observed, they allow scientists to measure subtle shifts in Phobos’ orbit over time. The moon’s tidal forces pull on the deep interior crust and mantle of the Red Planet; studying how much Phobos shifts over time reveals something about how resistant the crust and mantle are, and thus what kinds of materials they’re made of.”
At the same time, this ongoing orbital decay means Phobos is slowly drawing closer to Mars year by year. Scientists expect that eons from now, the doomed moon’s orbit will eventually send it crashing into the Martian surface or fragment it into impact debris.
A Historic Game of Cosmic Peekaboo
The transit observations also intersect with other rare alignments in the Martian sky. On July 2, Perseverance recorded an occultation when Earth slipped directly behind Phobos. During this 40-second sequence, our planet appeared as a bright dot gliding diagonally across the sky before vanishing behind the lumpy moon.
Mark Lemmon, a co-investigator of the rover’s Mastcam-Z instrument based at the Space Science Institute in Boulder, Colorado, planned the observation. At the time of the imaging, Earth sat approximately 195 million miles away, marking the first time in human history that an observer on the surface of another planet recorded Earth disappearing behind another world.
Broader Mission Goals at Jezero Crater
While capturing celestial mechanics in the Martian atmosphere, Perseverance continues its primary astrobiology mission on the ground. Managed by NASA’s Jet Propulsion Laboratory in California—built and managed for the agency by Caltech—the rover is tasked with characterizing the planet’s geology and past climate while searching for signs of ancient microbial life. The mission includes collecting and caching rock and regolith samples.
Subsequent missions planned by NASA in cooperation with the European Space Agency aim to return these sealed samples to Earth for in-depth laboratory analysis. Meanwhile, operations for the Mastcam-Z instrument are led by Arizona State University in Tempe, collaborating with Malin Space Science Systems in San Diego and the Niels Bohr Institute of the University of Copenhagen.
