The European Space Agency has released the latest pictures of the Martian moon Phobos, taken by the European Mars Express (MEX) probe during its recent flybys. On one flyby, MEX skimmed just 42 miles above the surface of Phobos, which is the closest any manmade object has ever gotten to the little Martian moon.

The image above is from a flyby that brought MEX within 63 miles of the surface; its High Resolution Stereo Camera took photographs that have a resolution of 14 feet per pixel. The images are being scrutinized by the Russian space agency as it tries to settle on a landing site for its ambitious Phobos-Grunt mission next year–the two potential landing sites are marked by red dots in the picture above. The Phobos-Grunt mission aims to collect a soil sample from Phobos, and then to return the sample to Earth for analysis.

Phobos is an odd little moon: it’s a potato-shaped rock measuring only 12 miles by 17 miles. Scientists believe the moon is relatively porous, but say its origin is still open to debate. Researchers suspect the moon is simply a collection of planetary rubble that coalesced around the Red Planet sometime after its formation. Another explanation is that it is a captured asteroid [BBC News]. Scientists believe that Phobos is being slowly pulled towards Mars, and tidal forces are expected to tear it apart one day.

The moon has drawn more attention lately, because it’s increasingly seen as a steppingstone for Mars-bound astronauts. Last month, NASA shifted its focus from sending humans back to the moon to a “flexible path” that includes the moons of Mars as potential destinations. The idea is that low-gravity locales such as Phobos (and Mars’ other moon, Deimos) should be easier to get to because they’re more accommodating for landing and ascent [MSNBC].

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Image: ESA/DLR/FU Berlin (G. Neukum)