Phobos Ridge Mars, the fourth planet of the Solar System. Phobos Ridge Phobos Ridge () is a rocky ridge of sandstones and shales forming the west side of Mars Glacier in the southeast corner of Alexander Island, Antarctica. The coast in this vicinity was first seen from the air by Lincoln Ellsworth on November 23, 1935, and roughly mapped from photos obtained on that flight by W.L.G. Joerg. This ridge was first surveyed in 1949 by the Falkland Islands Dependencies Survey (FIDS) and named by the United Kingdom Antarctic Place-Names Committee (UK-APC) for its association with adjacent Mars Glacier, Phobos being the
Formation and evolution of the Solar System This origin is indicated by the large sizes of the moons and their proximity to the planet. These attributes are impossible to achieve via capture, while the gaseous nature of the primaries also make formation from collision debris unlikely. The outer moons of the giant planets tend to be small and have eccentric orbits with arbitrary inclinations. These are the characteristics expected of captured bodies. Most such moons orbit in the direction opposite the rotation of their primary. The largest irregular moon is Neptune's moon Triton, which is thought to be a captured Kuiper belt object. Moons of solid Solar