Posted by tourdemars to Mars Express at March 4, 2010 11:03 AM

The European Mars Express (Mex) probe has made its closest flyby of the Martian moon Phobos, passing just 67km (42 miles) from its surface. No manmade object has ever been so near to the natural satellite. The approach is one of a series being made by Mex as it seeks to understand the origin of the moon. Previous flybys have indicated that Phobos has an extremely low density, suggesting that its surface probably hides many large interior voids. Scientists suspect the moon is simply a collection of planetary rubble that coalesced around the Red Planet sometime after its formation.