Pyramidal Mount Akhuna on Ceres may not be the only cryovolcano on its surface - astronomers have found traces of other, more ancient volcanoes in images from the Dawn probe, according to an article published in Geophysical Research Letters.
“We believe that we have enough 'evidence' to talk about the presence of many cryovolcanoes on Ceres in the past, which we do not see due to the fact that they were deformed. Imagine that there was only one volcano on Earth. This would be an extremely strange thing. Akhuna is a fairly young mountain, it was formed at most 200 million years ago. She just didn't have time to deform,”said Michael Sori of the University of Arizona in Tucson (USA).
The first images of Ceres taken by the Dawn probe in March 2015 after its arrival at the dwarf planet revealed two unusual structures that no one expected to see - the mysterious white spots in the Occator crater, which turned out to be traces of thick "brine", and the unusual pyramidal mountain Akhuna, towering over Ceres for four kilometers.
Both have forced scientists to revise theories describing the formation of Ceres and other such failed "embryos" planets. Only a year after the discovery of these structures, Christopher Russell, mission leader, and his colleagues declared that both were the product of cryovolcanism - eruptions of relatively warm water and thick brine from the interior of the dwarf planet onto its surface.
In addition, the discovery of this mountain made scientists wonder whether it is a unique landform for Ceres, generated by a single meteorite impact and the melting of its rocks, or such "pyramids" could have grown many times on the surface of a dwarf planet in the past, and then disappeared … Russell, Sori and their colleagues tested which of these theories was correct by creating a computer model of Ceres's interior.
Unlike Earth and other rocky planets, Ceres's bowels are mostly ice. At very low temperatures, ice becomes almost as strong as "real" rocks, but at the same time it remains highly fluid. This is manifested in the fact that over time, a mountain made of ice will spread over the surrounding plain, covering it with an even layer of frozen water. This process, as scientists suggested, could "erase" all traces of previous episodes of cryovolcanism from the surface of Ceres.
Guided by this idea, scientists calculated the time during which Mount Akhuna should disappear, and what traces of it may remain. As shown by these calculations, the height of the mountain will decrease rather quickly - by tens of meters for every million years. Accordingly, a typical cryovolcano can exist on the surface of Ceres for a very short time in geological terms - about 100 million years, after which its dome will become almost invisible from orbit.
"Flattened" structures of this type, as noted by geologists, they have already found on the surface of Ceres, including in the immediate vicinity of the "pyramidal mountain" itself. Now geologists are studying images from other regions of Ceres in search of other remains of cryovolcanoes, the discovery of which will help to understand how often they erupted on Ceres and what was the main "engine" of their activity.
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