Mars lake was discovered using the MARSIS radar on board the "Mars Express" orbiter, and the profiles were collected between May 2012 and December 2015. The lake is centered at 193°E, 81°S, a flat area that does not exhibit any peculiar topographic characteristics. It is mostly surrounded by higher ground except on its eastern side, where there is a depression. Mars has two relatively small (compared to Earth's) natural moons, Phobos (about in diameter) and Deimos (about in diameter), which orbit close to the planet. Asteroid capture is a long-favored theory, but their origin remains uncertain. Both satellites were discovered in
The Secret of the Martian Moons that unlocks Mars’ secret. A political controversy is raging on Earth as to whether or not to continue to support the Martian outpost, where Nelson’s father is research chief. Those in favor point to the marvelous machines found on Mars, any one of which could advance civilization eons, if their secret could be discovered. Going to work on the problem, Nelson finds out – in an interesting chain of events that characterizes a Mars basically like the canal-covered red planet we know it to be now – that the Martian moons Phebos (sic) and Deimos, are centers of tyrannical factions