The dwarf planet Ceres continues to amaze. The big surprise was in 2015 when NASA's Dawn spacecraft discovered a mini Everest-sized icy volcano.

The lonely volcano triggered thought waves on why it is so alone with no companions.

Here comes a new study that says Ahuna Mons is not alone and thousands of other ice volcanoes billions of years old might have flattened out, leaving it all alone. The 2.5-mile-tall ice volcano was a puzzle to scientists considering its solo nature and if the new theory holds up, Ahuna Mons must have many hidden volcanic siblings.

The findings came from a study to be published in Geophysical Research Letters, which said ice volcanoes aged millions or billions of years might have existed on Ceres. But they flattened out as time passed and left Ahuna Mons as a solitary structure.

"If you see one thing on a planet and nothing else that looks like nothing else, that's sort of strange," Michael Sori of the Lunar and Planetary Laboratory at the University of Arizona and the lead author told Inverse.

Icy Mystery

What has heightened the interest on the icy volcanoes of Ceres is its proximity to the sun, unlike other icy worlds that are too far from the hot star. Considering the position of Ceres as part of the asteroid belt, having icy volcanoes is quite unusual.

"Ceres is just barely far enough from the sun for this to work," Sori said.

The presence of ice volcanoes has been reported from dwarf planets and moons, like Pluto, Europa, Triton, Charon, and Titan. But they are far from the sun.

"But it's also why it makes it interesting because it's the warmest place where it's affected," he noted.

The researchers analyzed the question why Ahuna Mons is all alone. Is it the only volcano the Ceres ever had or is it the only one that is visible and others are invisible?

The researchers pitched the second possibility of invisibility of the peer volcanoes and said Ahuna Mons was left alone as other volcanoes vanished over millions of years.

"We think we have a very good case that there have been lots of cryovolcanoes on Ceres but they have deformed," Sori said.

How Did Other Volcanoes Vanish?

The researchers also put forward a hypothesis noting that unlike Earth, Ceres is bereft of an atmosphere that would wear down volcanoes through rain, ice, or wind. So the valid option is a flattening out of the volcanoes over eons of time in a process called "viscous relaxation."

The scientists explained that viscous relaxation is akin to a block of honey changing structure - first it's solid but takes a flat structure as time passes.

Also, Earth has a record of glaciers flowing out because of viscous relaxation. That process applies well to Ceres, considering the icy composition of the volcanoes, which turned flat as billions of years passed and the volcanic structures became indistinguishable.

"Ahuna Mons is at most 200 million years old. It just has not had time to deform," Sori said. If the flattening of the Ahuna Mons were to happen, it will be an average 30 to 160 feet for every million year it has existed, he added.

A study in 2016 found that the craters of Ceres are filled with water-ice. One school of opinion is that if humans start living in outer space and other planets, then the mining of Ceres and other icy worlds will be imperative for securing water.

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