Ceres and the disappearing ice volcanoes

Cryovolcanoes on the dwarf planet Ceres may be flattening out and disappearing over time, according to a new study.

A simulated view of Ahuna Mons using data from NASA’s Dawn mission. Did the cryovolcano’s companions simply flatten out over time?
Credit: NASA

Ahuna Mons, the tall, young and solitary ice volcano on dwarf planet Ceres, may have once had other volcanic companions that have disappeared over a period of millions of years, a study has suggested.

Cryovolcanoes - mountains of icy rock - may have existed on Ceres millions or even billions of years ago, but could have flattened out and effectively disappeared as a result of a process called viscous relaxation.

This process is based on the notion that almost any sold will eventually flow, given enough time. On Earth, for example, volcanoes do not flatten out over time because they are made of rock, but cryovolcanoes like Ahuna Mons on Ceres contain ice, which makes viscous relaxation possible.

If true, the theory could explain why Ahuna Mons, which is about half the height of Mount Everest on Earth, is all alone on the dwarf planet.

“Imagine if there was just one volcano on all of Earth,” says study leader Michael Sori of the Lunar and Planetary Laboratory at the University of Arizona. “That would be puzzling.”

Ahuna Mons appears in a mosaic of images taken by NASA’s Dawn spacecraft. Dawn took the images from 385km meters away.
Credit: NASA

Because Ceres has no atmosphere, any other cryovolcanoes that may have existed on the dwarf planet in the past could not have been worn down by wind or rain. This means that either Ahuna Mons is indeed a solitary cryovolcano, or that the viscous relaxation theory could be correct.

The team behind the study generated computer models to test their theory. They found that Ahuna Mons would need to consist of over 40 per cent water ice to be affected by viscous relaxation. If so, Ahuna Mons should be flattening at a rate of 30-160 feet per million years. This could explain why other older volcanoes elsewhere on Ceres could have disappeared.

“Ahuna Mons is at most 200 million years old. It just hasn’t had time to deform,” says Sori.

The next step for the team will be to attempt to identify the flattened remains of older cryovolcanoes on Ceres to support their theory.


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