It is in the main asteroid belt about 2.7 astronomical units (AU) from the Sun that we find the dwarf planet Ceres. Its ice volcano is one of its notable features, but it stands strangely alone. Scientists think they know why.
At 950 kilometers in diameter, Ceres is the largest body in the main asteroid belt. It is also the closest dwarf planet to the Sun and therefore the only dwarf planet in the inner solar system. On this star we find the Ahuna Mons, a cryovolcano which rises to 4,000 meters above sea level, making it the largest structure on the dwarf planet. But why is he so alone?
Generally, cryovolcanoes do not appear alone. For scientists from the University of Arizona, the Ahuna Mons was not alone a few million years ago, but the other cryovolcanoes would have collapsed. This would not be because of erosion as is the case with structures on land, but because they would have sunk.
This phenomenon is called “viscous relaxation”. Like moving glaciers on Earth, water ice can expand and change shape without melting. Thus, on Ceres, which is largely composed of water ice, the entire surface can flow. For scientists, this phenomenon can also extend to other icy stars such as Enceladus, Titan or Europe, but Ceres being the icy body closest to the Sun, it is particularly pronounced there.
» Heat also has a lot to do with it. It’s like putting a jar of honey in the microwave, the honey flows much faster than it does at room temperature “, explains Michael Sori, lead author of the study. The process of viscous relaxation can take millions of years. According to scientists, Ahuna Mons being a young cryovolcano about 200 million years old, the viscous relaxation would not have had time to act on it yet.
They should find out more by studying a bulging flat located near Ahuna Mons which could well be the remains of an ice volcano which gradually flattened over more than 500 million years.