Orcus Patera (Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)

Caption ESA:"Orcus Patera is an enigmatic elliptical depression located between Elysium and Olympus Mons.

This well-defined depression extends approximately 380 by 140 Km in a N/NE�S/SW direction. It has a Rim that rises up to 1800 mt above the surrounding Plains, while its Floor lies 400�600 mt below the surroundings. The term �Patera� is used for deep, complex or irregularly shaped Volcanic Craters such as the Hadriaca Patera and Tyrrhena Patera at the N/E margin of the Hellas Impact Basin.

However, despite its name and the fact that it is positioned near Volcanoes, the actual origin of Orcus Patera still remains unclear".