Untitled
In catching up with Cassini spacecraft imagery that had not been fully studied, researchers have spotted a mysterious dark spot near Jupiter's north pole and watched it develop over the course of more than two months.
They don't know what it is. But they released an animation of the phenomenon Wednesday.
The spot is similar to Earth's so-called "ozone hole" in the sense that it originated near the pole and was confined to the polar region, said Carolyn Porco, Cassini imaging team leader at the Southwest Research Institute. But, like the ozone hole, the Jovian spot is probably not an actual hole.
"It's not a physical hole," Porco said in a telephone interview. "It's probably a chemical disturbance, in which new hydrocarbon haze particles are created by auroral energetics."
The Jovian polar spot was larger than Earth itself. It developed inside Jupiter's auroral oval, a region near the pole where colorful atmospheric lights are generated by the interaction of gases with electricity. The spot whirled like a vortex as it grew and stretched out over time, appearing on the verge of dissipation near the end of the observations.
The images were made between Oct. 1 and Dec. 15, 2000, as Cassini approached Jupiter. The spacecraft's view of the planet was not directly over the pole, so the animation was reconfigured to show the event as though the viewer were looking down on the polar region from directly above.
Closer to the pole, a second and smaller strange spot is seen developing about halfway through the animation.
"It's probably a similar phenomenon," Porco said of the smaller spot. But, she pointed out, scientists haven't figured out what the larger spot is or how it formed. Jupiter is a wild place, with storms of all sizes raging in its atmosphere. The largest, called the Great Red Spot, is south of Jupiter's equator and spans more than 15,000 miles.
"UV waves are shorter," Porco said. "They scatter easily." Hence, the gas above the visible clouds appears bright and mostly featureless in the ultraviolet, and the familiar bands of clouds in Jupiter's equatorial region are invisible, as can be seen in the outer perimeter of the new animation. Only the very highest haze appears dark against the bright background.
"But near the poles, you see structures," Porco said. She said the dark spots are most likely the manifestation of haze developing high in the atmosphere rather than below it, where the main cloud layers exist. A haze also covers Jupiter's Great Red Spot, making it appear dark.
Further examination of the images returned by Cassini, a NASA-operated robot, together with examination of the data from other Cassini instruments, will eventually shed light on the mysterious spot, Porco said.
Cassini is now on its way to Saturn, where its primary mission will begin in 2004.
Click here to see the full animation
advertisement
