Astronomy Picture of the Day

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

2001 December 15
See Explanation.  Clicking on the picture will download
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Ganymede: Torn Comet - Crater Chain
Credit: Galileo Project, Brown University, JPL, NASA

Explanation: This striking line of 13 closely spaced craters on Jupiter's moon Ganymede was photographed by the Galileo spacecraft in 1997. The picture covers an area about 120 miles wide and the chain of craters cuts across a sharp boundary between dark and light terrain. What caused this crater chain? Remarkably, the exploration of the Solar System, has shown that crater chains like this one are not unique, though they were considered mysterious until a dramatic object lesson was offered by comet Shoemaker-Levy 9. In 1994 many denizens of planet Earth watched as huge pieces of this torn comet slammed into Jupiter itself in a spectacular series of sequential impacts. It is very likely that similar torn comets from the early history of the Solar System are responsible for this and other crater chains.

Tomorrow's picture: Dark Horse

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U.