Deimos and Phobos Interior Explorer that the moons of Mars may have formed after a huge collision with a protoplanet one third the mass of Mars that formed a ring around Mars. A third hypothesis is that they may have co-accreted with the parent planet. DePhine mission would explore the origin and the evolution of the two Martian satellites, by focusing on their interior structures and diversity. The mission would attempt to determine if Phobos and Deimos true siblings, originating from the same source and sharing the same formation scenario. It would also determine if both natural satellites are rubble piles or solid bodies, and
Phobos (moon) who studied Phobos and people and places from Jonathan Swift's "Gulliver's Travels". A number of craters have been named, and are listed in the following table. There is one named regio, "Laputa Regio", and one named planitia, "Lagado Planitia"; both are named after places in "Gulliver's Travels" (the fictional Laputa, a flying island, and Lagado, imaginary capital of the fictional nation Balnibarbi). The only named ridge on Phobos is "Kepler Dorsum", named after the astronomer Johannes Kepler. The orbital motion of Phobos has been intensively studied, making it "the best studied natural satellite in the Solar System" in terms of