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
Mars One before arrival at Mars) and a lander (see "Human Lander" below). In 2012, Mars One speculated that the Transit Living Module could potentially be designed and built by Thales Alenia Space. A concept study was produced by Lockheed Martin for a demonstration lander based on the 2008 "Phoenix" lander. In December 2013 Mars One awarded a contract to Surrey Satellite Technology for a study of the satellite technology required to provide 24/7 communication between Earth and the Mars base. Mars One proposed at least two satellites, one in areostationary orbit above Mars and a second at the Earth – Sun