Phobus

20 May 2010

At www.sciencenews.org May 14th ... Phobus, the larger moon of the planet Mars, appears to be porous - an amalgamation of space rubble (see Geophysical Research Letters May 16th). The density of Phobus is not dissimilar to asteroids but quite how Mars could have captured an asteroid without breaking it to pieces is an unknown.