* Phobos is the largest of the two Mars satellites with dimensions of 20 x 23 x 28 kilometers. ("Stars and Planets," p. 41.)

* It was Johannes Kepler who forecast the two satellites' existence in the year 1610, but actual confirmation that they existed did not come until the year 1877 when Asaph Hall discovered them. ("Planets," p. 76.)

* Deimos is the smaller of the two satellites of Mars, with dimensions of 10 x 12 x 16 kilometers. ("Stars and Planets," p. 41.)

* The gravity of Deimos (and Phobos) is virtually zero. Both the satellites are more like asteroids than planet-like entities. ("The Planets," p. 77.)

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