Jupiter Loses Big Belt

Two wide stripes—known as the equatorial belts—normally circle the huge planet, products of the fast-moving jet streams that roar through Jupiter's atmosphere.

But pictures of Jupiter taken by an amateur astronomer show that sometime during the past couple weeks, the south equatorial belt completely faded from view.

"The basic view of Jupiter is of two dark belts. Now there is only one," said Alan MacRobert, senior editor of Sky & Telescope magazine.

"This is the most obvious change on Jupiter that I can recall," he said, adding that anyone with a backyard telescope should be able to see the difference. "Any instrument powerful enough to show any of Jupiter's surface features will easily reveal the change."

However, the planet's "belt buckle" remains: The lost stripe "means that Jupiter's Great Red Spot is now floating all alone in whiteness, whereas usually it is in an indentation in the south equatorial belt," MacRobert said.

The spot—actually a raging storm three times bigger than Earth—is rarely brick red, he added, and often becomes quite pale. MacRobert characterizes its current color as "somewhat orangy." (Find out why the Great Red Spot has been shrinking.)

Jupiter's Dark Belt Lost to Light Cloud Cover?

Despite the dramatic change on Jupiter, the lost belt doesn't concern experts. The planet has lost this stripe before, most recently in the 1970s and the early '90s. So far, the stripe has always reappeared.

Astronomers are, however, somewhat stumped for a complete explanation.

A dozen or so jet streams move alternately east-west and west-east on Jupiter, said planetary scientist Andrew Ingersoll of the California Institute of Technology. The clouds in between these jet streams create the planet's multicolored stripes and swirls.