Scientists used to think that things were pretty chill over in the south hemisphere of Uranus. In fact, they thought it was one of the calmest regions of any of the gas giants. But in analyzing images taken nearly three decades ago by NASA's Voyager-2 spacecraft, researchers think they've found a kerfuffle of activity — which might indicate that there's something unusual about the planet's interior.

If you look at these old photos of Uranus, the planet appears to be a stark, featureless ball. And even to scientists, who were able to identify more lively features of the gas giant, it was still considered pretty bland.

But when University of Arizona astronomer Erich Karkoschka took another look, he saw a different story. He presented his findings this week at the meeting of the Division for Planetary Sciences of the American Astronomical Society.

Karkoshchka believes that Uranus's southern hemisphere rotates in a way never before seen in gas giants. A gas planet's thick atmosphere, filled with clouds, typically shows the same rate of rotation at the top and bottom. But on Uranus, it seems, the southern hemisphere is cycling much more quickly than up north — as much as 15 percent faster.

"The unusual rotation of high southern latitudes of Uranus is probably due to an unusual feature in the interior of Uranus," Karkoshcka said in a statement. "While the nature of the feature and its interaction with the atmosphere are not yet known, the fact that I found this unusual rotation offers new possibilities to learn about the interior of a giant planet."

Data on gas giants in general are few and far between, so anything that Karkoshcka can glean about Uranus's core would help scientists understand the other planets like it.

"Most of the more than a thousand planets discovered around other stars are similar in size to Uranus," Karkoschka said. "They are too far for us to be able to measure their rotational profiles for the foreseeable future, but with an improved knowledge about Uranus, we might be better able to draw conclusions about their interior structure."

The coolest thing about the work is that it relies on old images. Voyager-2 is long past Uranus these days, but Karkoshchka has shown that its old photos are worth another visit.

Read More: