Astronomy Picture of the Day

Discover the cosmos! Each day we feature a different image or photograph of our fascinating universe, along with a brief explanation written by a professional astronomer.

July 15, 1995
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The Crater Chain
Picture Credit: NASA, Voyager Team

Explanation: NASA's robot spaceprobe Voyager 1, took this closeup image of the surface of Jupiter's crater scarred moon Callisto in 1979. A mysterious chain of craters is seen to extend diagonally across the image (upper left to lower right). What could cause the craters to line up in such a regular fashion? Scientists were at a loss to explain this crater chain along with several other chain like features observed on Callisto's surface. Fifteen years later, with the discovery of Comet Shoemaker-Levy 9, also known as the "string of pearls" comet, the mystery was solved. Comets whose orbits stray too close to Jupiter are torn apart by the strong gravity. When the individual pieces, strung out along the orbital path of the comet hit an object like Callisto, the sequence of impacts produces a crater chain.

For more information about the picture see the Split Comet Studies Page.

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Astronomy Picture of the Day is brought to you by Robert Nemiroff and Jerry Bonnell . Original material on this page is copyrighted to Robert J. Nemiroff and Jerry T. Bonnell.