Origin of Phobos and Deimos by the impact of a Vesta to Ceres sized body with Mars

The origin of Phobos and Deimos, the two small moons that orbit close to the surface of Mars, have been hotly debated by scientists for decades.
A violent impact between Mars and another planet-sized object resulted in the birth of the Red Planet’s two moons, according to a new study.

As the new study suggests the Martian moons may have been created in the aftermath of a cataclysmic collision between early Mars and an object with a mass somewhere between that of the dwarf planet Ceres, and the asteroid Vesta.
When an object, somewhere between 600 and 800 kilometers in size, smashed into the side of Mars, it produced a disc of orbiting debris that began to orbit the planetary body.
The outer portions of the disc then accumulated to form Phobos and Deimos while the debris closer to the planet spiralled inwards and was assimilated into the planet.
The model also predicts that the two moons are derived primarily from material originating in Mars, so their bulk compositions should be similar to that of Mars for most elements.
However, heating of the ejecta and the low escape velocity from Mars suggests that water vapour would have been lost, implying that the moons will be dry if they formed by impact.
The scientists behind the new research turned to advanced hydrodynamical computer modelling in an attempt to identify a scenario in which the small moons could have formed in the orbit of the Red Planet. First, the team ran detailed simulations designed to reveal the nature of a circum-Martian disk of debris from which Phobos and Deimos could have coalesced.
The real confirmation of this impact model could come from an upcoming mission from JAXA, Japan's space agency. It will launch the Martian Moons eXploration early next decade and scoop up bits of matter from Phobos and send it back to Earth.
As for the other long-lost moons?
All they are is dust in the wind.

Phedias Hadjicharalambous.
Cyprus Astronomy Organisation