Modeling reveals how dwarf planet Ceres is fueling unexpected geological activity

For a long time, our sight of Ceres was hazy, said Scott King, a geoscientist at Virginia Tech College or University of Science. A dwarf planet and the largest body found in the asteroid belt — the region between Jupiter and Mars dotted with hundreds of thousands of asteroids — Ceres had no distinct surface features in existing telescopic observations of Earth.

Then, in 2015, the misty orb that was Ceres appeared. This view was astounding to scientists such as King. including its composition and buildings, which revealed unexpected geological activity.

Scientists had seen the general size of Ceres in previous observations. He was so small that it was assumed he was inactive. Instead, Dawn discovered a large plateau on one side of Ceres that covered a fraction of the dwarf planet, similar to what a continent might occupy on Earth. Around him were fractures in the rocks clustered in one place. And there were visible traces of an ocean world: deposits all over the area where minerals had condensed as the water evaporated – the mark of a frozen ocean.

A professor in the Department of Geosciences, King, who mainly studies larger bodies such as planets, wanted to know how a body as small as Ceres could generate the heat needed to power this form of activity. geological and explain the floor characteristics captured by Aube.

Thanks to modeling, he and a team of scientists from several universities as well as the United States Geological Survey and the Planetary Science Institute discovered that the decay of radioactive elements inside Ceres could keep it active. Their findings were recently published in American Geophysical Union Improvements.

King’s study of large planets such as Earth, Venus and Mars had always shown him that planets begin to heat. The collision between the objects that form a planet creates this initial heat. Ceres, on the other hand, was never large enough to become a planet and generate heat in the same way, King said. To find out how it could still generate enough heat to fuel geologic activity, he used theories and computational tools previously applied to larger planets to study Ceres’ interior, and he searched for evidence that could back it up. its patterns in the data returned by the Dawn mission.

The team’s model of the interior of the dwarf planet showed a unique sequence: Ceres started cold and warmed up due to the decay of radioactive elements such as uranium and thorium – which alone were enough to fuel its activity – until the interior became unstable.

“What I would see in the model is that, all of a sudden, part of the inside would start to heat up and move up and then the other part would move down,” King said.

This instability could explain some of the surface features that had formed on Ceres, as revealed by the Dawn mission. The great plateau had formed on one side of Ceres with nothing on the other side, and the fractures were clustered in one place around it. The focus of features in a hemisphere signaled to King that the instability had occurred and left an obvious impact.

“It turned out that you could show in the model that where one hemisphere had this instability going up, it would cause extension at the surface area, and that matched those patterns of fractures,” King said. the basis of the team’s model, Ceres did not follow the typical pattern of a hot-first-cold-second planet, with its own cold, hot-and-cold-again pattern. “What we’ve shown in this paper is that radiogenic heating alone is enough to create interesting geology,” King said.

He sees similarities with Ceres in the moons of Uranus, which a study commissioned by NASA and the Nationwide Science Foundation recently deemed high priority for a major robotic mission. With further improvements to the model, he looks forward to exploring their interiors as well.

“Some of these moons are not too different in size from Ceres,” King said. “I think applying the model would be really exciting.”

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