Martian Moon Phobos & A 'Mini' Planet Saturn | Europe's Mars Express

Martian Moon Phobos & A 'Mini' Planet Saturn | Europe's Mars Express

Can you spot planet Saturn here?

Phobos is a small, irregularly shaped object with a mean radius of 11 km (7 mi). Phobos orbits 6,000 km (3,700 mi) from the Martian surface, closer to its primary body than any other known planetary moon. It is so close that it orbits Mars much faster than Mars rotates, and completes an orbit in just 7 hours and 39 minutes. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 hours and 15 minutes or less, and set in the east, twice each Martian day.

Phobos is one of the least reflective bodies in the Solar System, with an albedo of just 0.071. Surface temperatures range from about −4 °C (25 °F) on the sunlit side to −112 °C (−170 °F) on the shadowed side. The defining surface feature is the large impact crater, Stickney, which takes up a substantial proportion of the moon's surface. The surface is also home to many grooves, with there being numerous theories as to how these grooves were formed.

The European Space Agency's Mars Express Mission (2003-2026) was launched on June 2, 2003, from Baikonur, Kazakhstan, aboard a Russian Soyuz rocket with a Fregat upper stage. In addition to being Europe’s first mission to Mars, Mars Express is the first fully European mission to any planet. The orbiter has been successfully performing scientific measurements since early 2004, namely, high-resolution imaging and mineralogical mapping of the surface, radar sounding of the subsurface structure down to the permafrost, precise determination of the atmospheric circulation and composition, and study of the interaction of the atmosphere with the interplanetary medium. Due to the valuable science return and the highly flexible mission profile, Mars Express has been granted several mission extensions.

The orbiter will continue its study of Mars until at least the end of 2026 with an indicative extension from January 1, 2027 to December 31, 2028 to support the Japan Aerospace Exploration Agency (JAXA)-led Mars Moons eXploration (MMX) mission (Japan), followed by two years of post-operations.

Mars Express has conducted data relay for seven rovers and landing platforms and has supported scientific work with a further five orbiters.

The past 20 years of observations from Mars Express have solidified our picture of Mars as a once-habitable planet with warmer and wetter epochs that may have been oases for ancient life. This is a monumental shift from our previous view of the planet that characterized it as an eternally cold and arid world.

Learn more: 
https://www.esa.int/Science_Exploration/Space_Science/Mars_Express

Credit: ESA/DLR/FUBerlin/AndreaLuck CC BY

License: creativecommons.org/licenses/by/4.0/deed.en
Raw Data: HR898_0005_SR3, 02-04-2026
Image Processing: Andrea Luck
ESA Release Date: Sept. 15, 2026

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