NASA/JPL/University of Arizona

The Io torus is a doughnut-shaped ring of gas surrounding Jupiter. The gas originates from the many volcanoes on Io, Jupiter's closest large satellite. The volcanoes on Io spew out sulfur and sulfur dioxide. These particles are ejected into space and are stripped of their electrons (or ionized). The particles (ions) then become trapped in Jupiter's magnetic field. Because the field rotates with the planet, the particles make a complete circle around the planet every ten hours, the rotational period of Jupiter.

About the images

This video clip was compiled from 235 exposures taken in November 2000 by the Cassini spacecraft. The exposures were made using the ultraviolet imaging spectrograph while Cassini was about 50 million kilometers (30 million miles) from Jupiter. The moving dot above and below the image indicates the rotation of the planet. As the planet rotates, the torus appears to wobble because Jupiter's magnetic field is tilted relative to its poles.

Ellen Cohen