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Jupiter Gains Mass but Loses a Belt

Jupiter Gains Mass but Loses a Belt
Jupiter Gains Mass but Loses a Belt When this year's Jupiter observing season began, the giant planet had a surprise in store for astronomers: one of its two iconic, dark equatorial belts had vanished, turning from reddish brown to pale white. While watching the unusual beltless planet on the night of June 3, Australian amateur astronomer Anthony Wesley spied a bright flash on that same belt, which is now understood to be the mark of a small asteroid, about 10 meters in diameter, burning up in the atmosphere. Anthony Wesley

In retrospect, it was clear that the belt had been fading since late last year. This fading event has been observed at least 14 times since 1919 and is usually followed by the belt's reappearance a year or two later; the Pioneer flybys in 1973 and 1974 occurred during a previous fade.

Wesley's observation was confirmed by Christopher Go from the Philippines. On August 20, another flash was spied by Japanese amateur Masayuki Tachikawa. Neither flash left any permanent mark on Jupiter's atmosphere; by the time the world's great telescopes -- including Hubble, Gemini, and Keck -- were trained on the planet hours afterward, no sign of either impact remained.