A dark scar floats during the extreme southern hemisphere of Jupiter in this Hubble Space Telescope image. The scar appeared in July 2009, the likely result of a rocky asteroid ramming into the giant planet. In this image, the scar, which consists of dark material blasted onto the planet's cloudtops, is wider than Earth. Amateur astronomers have observed at least two smaller impacts on Jupiter since this one. The planet's dynamic atmosphere quickly swallows them, however. [NASA/STScI]
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Jupiter at Opposition
It's been a weird year or so for Jupiter, the largest planet in the solar system. Last summer, it got socked by a comet or asteroid. A few months ago, it got hit again. And in between, one of its dark belts faded from view.
Although you can't follow such events without a telescope, Jupiter itself is in good view right now. It's lining up opposite the Sun, so it rises at sunset and remains in view all night. It's brightest for the year, too -- only the Moon and the planet Venus outshine it, so you can't miss it.
The first impact on Jupiter took place last July. No one saw it happen, but they did see the aftermath -- a dark bruise in the planet's atmosphere. It was similar to the bruises left when the fragments of a comet rammed into Jupiter in 1994. This bruise probably was inflicted by a rocky asteroid perhaps a third of a mile wide. The impact created a big explosion, with dark debris spreading across millions of square miles. The bruise lasted for weeks.
The second impact took place this June -- and this one was seen. Amateur astronomers saw a bright flash on the planet. But no bruise appeared, leaving scientists to ponder just what happened. It's possible that the explosion took place too high in the atmosphere to spread dark debris -- leaving Jupiter with no bruise from this cosmic collision.
One other dark mark that went missing from Jupiter is one of its cloud belts. More about that tomorrow.
Script by Damond Benningfield, Copyright 2010
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