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
The Secret of the Ninth Planet The Secret of the Ninth Planet The Secret of the Ninth Planet is a science-fiction novel written by Donald A. Wollheim and first published in the United States in 1959 by the John C. Winston Co. Wollheim takes his heroes on a grand tour of the solar system as that team struggles to prevent an alien force from blowing up the sun. This is the last of three juvenile novels that Wollheim wrote for Winston, the other two being "The Secret of Saturn's Rings" and "The Secret of the Martian Moons". This is one of the thirty-five juvenile novels that