Scientists were puzzled when NASA’s Dawn spacecraft, which entered orbit around dwarf planet Ceres in March 2015, revealed the presence of a single cryovolcano (ice volcano) on the entire 590-mile (950-km) wide world.
Named Ahuna Mons, that ice volcano rises to a height of two and a half miles (four km) and is 10.5 miles (four by 17 km) wide with a dome-shaped surface.
Thinking the presence of just one volcano unusual, Michael Sori of the Lunar and Planetary Science Laboratory at the University of Arizona, along with a team of researchers, decided to search for evidence that Ceres once harbored other, older cryovolcanoes that subsequently flattened out over millions of years.
Such flattening can occur through a process called “viscous relaxation.” Many solid materials on the surface of a planet eventually flow, leading them to flatten and relax.
Earth’s volcanoes and mountains do not experience this process because they are composed of rock. In contrast, Ahuna Mons has a high content of water ice, which would flow over time.
Using computer simulations, Sori and his colleagues determined that a minimum water ice composition of 40 percent would be sufficient to flatten a cryovolcano like Ahuna Mons between 33 and 165 feet (between 10 and 50 meters) over a period of one million years.
Over longer periods of several hundred million to several billion years, older cryovolcanoes on Ceres’ surface could have been completely flattened.
No older than 200 million years, Ahuna Mons has not had sufficient time for this process to have been completed, Sori said.
He and his team plan on studying photos of Ceres’ surface captured by Dawn to hunt for evidence of ancient cryovolcanoes.
“It would be fun to check some of the other features that are potentially older domes on Ceres to see if they fit in with the theory of how the shapes should viscously evolve over time,” said Kelsi Singer of the Southwest Research Institute in Boulder, Colorado.
Singer was not involved with the study but shares an interest in cryovolcanoes, which are suspected to exist on several solar system worlds, including Pluto, Charon, Triton, and Titan.
Sori’s study has been accepted for publication in the journal Geophysical Research Letters.