Is the Ceres bright spot caused by a plume of gas?

With NASA’s Dawn spacecraft only recently entering orbit around Ceres, it’s early days but we are getting the first hints of an explanation of the mysterious bright spot on the largest asteroid, Emily Lakdawalla reports on her Planetary Society blog.

Reporting from the 46th Lunar and Planetary Science Conference, she reveals the early thinking by Andreas Nathues of the Max Planck Institute, who believes the feature could be some sort of plume of gas.

Previous speculation has suggested that it could be some sort of volcano-like feature.

Lakdawalla reports from Nathues’ lecture:

[The bright spot] is located in the floor of a crater 80 kilometers in diameter. From its behavior as the globe rotates, he said, the bright feature appears to lie in a depression. The images that have been released to the public from the rotation animation do not show all of the photos of the bright feature, so the next point concerns images that I can’t show you.
“What is amazing,” he said, “is that you can see the feature while the rim is still in front of the line of sight. Therefore we believe at the moment that this could be some kind of outgassing. But we need higher resolution data to confirm this.”
What he is saying is that as Ceres’ globe rotates and the 80-kilometer crater’s rim rotates into view, that rim should block our ability to see the bright feature on the floor of the crater. However, the bright feature is already visibly bright as the crater begins to rotate into view. Therefore, it must be vertically above the rim of the crater: it must be some kind of plume. “During the day,” Nathues went on, “the feature evolves: it brightens. At dusk it gets fainter; at late dusk it disappears completely. We see this for cometary activity.”

But we won’t know for sure until Dawn moves from the night side of Ceres.

Obviously, active outgassing on Ceres would be a big deal, if it really exists. Fortunately, Dawn will get much closer and will take much better images, which will hopefully confirm this discovery!

Ceres gas 2
An image taken by NASA’s Dawn spacecraft of dwarf planet Ceres from a distance of nearly 46,000 kilometers. It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin.

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