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
Moons of Uranus to be responsible for the heating that caused substantial endogenic activity on Miranda and Ariel. One piece of evidence for such a past resonance is Miranda's unusually high orbital inclination (4.34°) for a body so close to the planet. The largest Uranian moons may be internally differentiated, with rocky cores at their centers surrounded by ice mantles. Titania and Oberon may harbor liquid water oceans at the core/mantle boundary. The major moons of Uranus are airless bodies. For instance, Titania was shown to possess no atmosphere at a pressure larger than 10–20 nanobar. The path of the Sun in the