Moons of Mars formed a large moon. Gravitational interactions between this moon and the outer ring formed Phobos and Deimos. Later, the large moon crashed into Mars, but the two small moons remained in orbit. This theory agrees with the fine-grained surface of the moons and their high porosity. The outer disk would create fine-grained material. While many Martian probes provided images and other data about Phobos and Deimos, only few were dedicated to these satellites and intended to perform a flyby or landing on the surface. Two probes under the Soviet Phobos program were successfully launched in 1988, but neither conducted the
Transit of Phobos from Mars 57.75 seconds to get a time of 20:49:02.4 UTC for the center of the shadow. Putting in the longitude/latitude/altitude coordinate values -124,14,0 into JPL Horizons gives an expected time of 20:49 for the transit, which is in good agreement once again. On 1 September 1999 the distance between the Earth and Mars was 9.9 light-minutes. Transit of Phobos from Mars A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Sun's disc for an observer on