Ice volcanoes are comparable to regular ones — except instead of being formed from molten rock, they are instead composed of frozen liquids like ammonia, methane and water. These materials typically erupt out as liquid or vapour plumes into extreme environments the feature conditions either at or below their respective freezing points, before turning solid. So-called cryovolcanic activity has been observed in several places in our Solar System, Including on Jupiter’s moon Europa, Saturn’s moon Titan and the dwarf planet Ceres.
The evidence for Pluto’s cryovolcanic activity was captured by NASA’s New Horizons spacecraft during its flyby of the planet back in 2015.
Images taken by the spacecraft have revealed that the dwarf planet’s surface is made up of terrains of various ages — with ancient, heavily cratered regions on one hand and far younger areas with few-to-no impact sites on the other.
One of the latter regions is of particular interest, being dominated by enormous rises with irregular flanks, creating a topography that the researchers said does “not exist anywhere else in the imaged solar system.”
Analysis of these features and the composition of the area suggests that the rises were created by cryovolcanism — with the landscape being made mainly of water ice.
The area of interest lies to the south-west of “Sputnik Planitia” — an impact basin of around 620 miles in diameter that has become filled with a vast sheet of ice.
According to the team, the region is peppered with various cryovolcanic domes, which range up to 4.3 miles high — and can reach anywhere between 6–93 miles in diameter.
Some of the domes, they noted, appeared to have merged to form larger features.
In fact, one of the structures — named Wright Mons in honour of the American aviation pioneers, the Wright brothers — is estimated to have a similar volume to that of Hawaii’s Mauna Loa, one of the largest volcanoes on the Earth.
The researchers believe that the formation of the cryovolcanic terrain would have required several individual eruption sites — not to mention a large volume of material.
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According to the team, the fact that the area is free from impact craters — unlike other terrains on Pluto — suggests that the cryovolcanic activity must be relatively recent.
This, they added, may change our understanding of the temperature and thermal properties of the dwarf planet’s internal structure.
The team concluded: The existence of these massive features suggests Pluto’s interior structure and evolution allows for either enhanced retention of heat or more heat overall than was anticipated before New Horizons, which permitted mobilisation of water-ice-rich materials late in Pluto’s history.”
The full findings of the study were published in the journal Nature Communications.