Shield volcano Mars are very similar to the shield volcanoes on Earth. Both have gently sloping flanks, collapse craters along their central structure, and are built of highly fluid lavas. Volcanic features on Mars were observed long before they were first studied in detail during the 1976–1979 Viking mission. The principal difference between the volcanoes of Mars and those on Earth is in terms of size; Martian volcanoes range in size up to high and in diameter, far larger than the high, wide Hawaiian shields. The highest of these, Olympus Mons, is the tallest known mountain on any planet in the solar
Doom Mons Titanean "mountains" are little more than hills. However, some of these mountains rise to some several hundreds of meters high. Doom Mons is currently believed to be possibly the largest Titanean mountain range and with the eponymous peak one of the highest; the title of highest peak on Titan is thought to be held by the Mithrim Montes, which may have been formed by global contraction. Doom Mons is believed to be a twin-peak that rises above the relatively flat surrounding plain, and a probable massive cryovolcano. It has a 500–600 m deep indentation on its western side, containing a