Ceres' Lonely Ice Volcano Might Have Company

[Buster's Uncle]

Ceres' Lonely Ice Volcano Might Have Company
Popular Mechanics
Sophie Weiner  February 6, 2017



Photo credit: NASA



From Popular Mechanics

"Imagine if there was just one volcano on all of Earth," Michael Sori of the Lunar and Planetary Laboratory at the University of Arizona in Tucson said to the American Geophysical Union. "That would be puzzling."

Sori was drawing a comparison to Ceres, which orbits the sun in the Asteroid Belt between Mars an Jupiter. Researchers recently discovered a 2.5-mile-tall cryovolcano, or frozen ice volcano, on the dwarf planet. As Sori suggests, what's strange about this discovery is that the volcano, Ahuna Mons, is one of a kind. The rest of Ceres' surface is flat. This posed a puzzling question to scientists: Is Ahuna Mons truly the only volcano that has ever graced Ceres' surface? Or is it merely the only one that's currently visible?

A new study in Geophysical Research Letters, authored by Sori, explains a theory that may answer this question. The researchers' idea is that the lone volcano is not truly on its own; rather, all the other volcanoes have been flattened out 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 says.

There's good precedent for this finding. Many other planets are known to have at one point hosted volcanoes that disappeared over time. But the strange thing about Ceres is that it has no atmosphere, and therefore no wind or elements to wear down a mountain the way they would on other planets. This new study points to an alternate explanation, something called viscous relaxation.

Viscous relaxation is the idea that any solid will eventually "flow," like glaciers on Earth, which move over extremely long periods of time. Eventually any solid will flow into a flattened state, even if it takes millions and millions of years.

Sori and colleagues ran an experiment to see if viscous relaxation of Ceres' ice volcanoes was possible. In their model, they tested different percentages of ice in the theoretical volcano's make up, from 40 to 100 percent.

The American Geophysical Union describes the findings:

Ahuna Mons would need to be composed of more than 40 percent water ice to be affected by viscous relaxation, they found. At this composition, Sori estimates that Ahuna Mons should be flattening out at a rate of 10 to 50 meters (30 to 160 feet) per million years.

These results mean that if Ahuna Mons is more than 40% water, it's totally possible that other volcanoes on Ceres that previously existed have been flattened over the millennia. But Ahuna Mons itself it too young, thus why its visible to us now. "Ahuna Mons is at most 200 million years old. It just hasn't had time to deform," Sori says.

Sori's team will now look at the surface of Ceres to see if they can identify any areas that are likely deformed cryovolcanoes. This knowledge will give scientists a better idea of how Ceres and similar planets are formed and the kind of geological formations that are possible on planets in our solar system.

Source: Geophysical Research Letters


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