The mechanism for the formation of this mountain is believed to be cryovolcanism, where liquid salty water rather than lava is ejected. On Ceres, these salt-water eruptions are produced due to the pressure from the asteroid’s icy surface. As the erupted water evaporated away under the vacuum of space, it left behind salt deposits. Ahuna Mons is the nearest known cryovolcano to the Sun.
3. Io
Io is the innermost large moon of Jupiter and orbits the host planet once every 43 hours. It was discovered by Galileo in 1610 and is about the same size as Earth’s Moon. But unlike our quiet celestial neighbour, Io is the most volcanically active body in the Solar System. Io has been surveyed several times by robotic spacecraft and by telescopic observations from Earth.
Its surface is a distinctive yellow-red colour owing to vast deposits of sulphur, much of which has been erupted from the more than 400 active volcanoes on its surface. The source for much of the energy for all these volcanoes comes from tidal forces due to the proximity of the second nearest large Jovian moon, Europa, and the largest Jovian moon, Ganymede.
Io completes two orbits of Jupiter for every one orbit by the moon Europa, and four orbits of Jupiter for every one orbit of Ganymede. Hence, Io frequently lines up with one of these other moons and is stretched by the powerful gravity of Jupiter in one direction and the aligned gravitational fields of the outer moons in the other.
This continuous flexing releases large amounts of heat, which helps to keep the interior of Io molten and drive volcanism on its surface. Some of the most spectacular volcanoes of Io erupt plumes of material hundreds of miles above Io’s surface, as seen in the animation below.
