On 30 September 2024, NASA’s Perseverance rover turned its Mastcam-Z camera towards the Martian sky, capturing a remarkable view of Phobos, Mars’ small, irregularly shaped moon, as it passed in front of the Sun in a partial eclipse. This event, observed on what scientists refer to as Sol 1285 of the mission, showcased the shadowy outline of Phobos—a potato-shaped rock—highlighted against the Sun’s bright disk.

A Unique View of Mars’ Potato-Shaped Moon

Unlike Earth’s spherical moon, Phobos has a distinctly irregular form, closely resembling an asteroid. Spanning about 17 by 14 by 11 miles, it follows a unique, elliptical orbit around Mars at a mere 3,700 miles from its surface. By comparison, Earth’s Moon is nearly 239,000 miles away, making Phobos seem incredibly close to Mars. Its proximity and rapid orbit allow it to circle Mars thrice daily, creating frequent but brief eclipse opportunities for Martian observers.

Tracing the Origins of Phobos

The origin of Phobos remains a mystery in planetary science. While its appearance hints at an asteroid, many researchers believe Mars’ gravity didn’t capture Phobos but rather may have formed alongside the planet or in the aftermath of a colossal impact event. The nearly perfect orbit that Phobos maintains around Mars is one of the main reasons scientists have leaned away from the asteroid capture theory, as captured bodies often exhibit irregular orbits.

Perseverance’s Continued Observation of Martian Eclipses

This isn’t the first time Perseverance has observed Phobos’ transit. The rover has previously photographed similar eclipses in April 2022 and February 2024. Other Mars rovers, such as NASA’s Spirit and Opportunity, captured images of Phobos eclipses in 2004, and Curiosity recorded this event in 2019.