The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the Mars Reconnaissance Orbiter, recorded at a resolution of about seven meters per pixel.
Diameter 22.2 km
18.8 mi.
Distance from primary 9,377 km
5,826 mi.
Nickname(s) FO BO S

Phobos is the first moon of Mars. Discovered in August 18, 1877 by Asaph Hall.