Just a little more than a year ago, the small spot on Jupiter was a pale white; now it matches the reddish hue of its bigger sibling, the Great Red Spot, and boasts 400-mph winds, according to new data from the Hubble Space Telescope.

Both spots are actually fierce storms in Jupiter's atmosphere. While the red spot — at three times the size of Earth — is much more noticeable, strange things are happening to the smaller spot.

Scientists aren't quite sure what's happening to the smaller storm, nicknamed the Little Red Spot or Red Spot Jr. but officially called "Oval BA."

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It probably gained strength as it shrunk slightly, the same way spinning ice skaters go faster when they move their arms closer, said NASA planetary scientist Amy Simon-Miller.

Her findings from the Hubble data were published in the astronomical journal Icarus.

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As the storm has grown stronger, it's probably picked up red material from lower in the Jovian atmosphere, most likely some form of sulfur which turns red as part of a chemical reaction, she said.

The color change took astronomers by surprise. They figure more surprises are in store as the solar system's largest planet goes into hiding from Earth's prying eyes until January, moving behind the sun.

"We found that Jupiter tends to do interesting things behind the sun and we can't see it," Simon-Miller said.