Perseverance rover captures rare Phobos transit across the Sun from Martian surface

NASA's Perseverance rover has captured a rare celestial event: the transit of Mars' moon Phobos across the face of the Sun. The images, taken on August 12, 2026, by the rover's Mastcam-Z camera, have provided unprecedented accuracy in mapping the moon's orbital parameters, pinpointing them within 100 meters.

Photo: NASA by NASA’s Goddard Space Flight Center/Conceptual Image Lab, https://creativecommons.org/public-domain/pdm/

Solar flare

A Fleeting Shadow Across the Sun

To capture the phenomenon safely, the rover employed specialized solar filters, safeguarding its sensitive optics from overheating and damage. Due to Phobos' irregular shape and its rapid movement relative to Martian rotation, the transit appears as a swift-moving dark silhouette against the solar disk. This dramatic event unfolds in less than a minute.

Martian Vantage Point Yields Critical Data

Observations conducted from the Martian surface offer a distinct advantage over Earth-based telescopes due to the minimal distance to the celestial bodies involved. Precisely tracking Phobos' coordinates is crucial for understanding the long-term evolution of its orbit. This data provides vital insights into the internal structure of both Mars and its moon. The tidal forces exerted by Mars on Phobos influence the moon's trajectory, offering clues about the rheology, or deformability, of the Martian mantle.

Astronomer Pavel Gromov highlights the Sun's role as an "ideal reference background" for highly precise measurements. Such detailed information is indispensable for the planning of future missions aiming to land on Phobos.

Beyond Orbital Dynamics: Solar Activity and Future Missions

These detailed images also contribute to monitoring solar activity. Previously, Perseverance had documented sunspots on the star's far side, information not visible from Earth. These observations enabled accurate predictions of powerful solar storms.

Currently, Perseverance is engaged in nighttime imaging of Phobos against the backdrop of stars. This ongoing observation is essential for determining all six orbital parameters, as daytime transits only provide a partial dataset. The compiled data will be instrumental for the upcoming Mars Moons Explorer (MMX) mission, slated for launch in October 2024. The MMX mission aims to collect samples from Phobos and return them to Earth by 2031.

Source: This commentary was adapted from an original Russian-language publication by Pravda.Ru.