Comet Shoemaker–Levy 9 rarity: one post-impact study estimated that comets in diameter impact the planet once in approximately 500 years and those in diameter do so just once in every 6,000 years. There is very strong evidence that comets have previously been fragmented and collided with Jupiter and its satellites. During the Voyager missions to the planet, planetary scientists identified 13 crater chains on Callisto and three on Ganymede, the origin of which was initially a mystery. Crater chains seen on the Moon often radiate from large craters, and are thought to be caused by secondary impacts of the original ejecta, but the
The Elves and the Shoemaker The Elves and the Shoemaker "The Elves and the Shoemaker" is an often copied and re-made 1806 story about a poor shoemaker who receives much-needed help from elves. The original story is the first of three fairy tales, contained as entry 39 in the German "Grimm's Fairy Tales" under the common title "Die Wichtelmänner". In her translation of 1884 Margaret Hunt chose The Elves as title for these three stories. The Aarne–Thompson folklore classification system categorizes the story as type 503*: Helpful Elves and also as a migratory legend, type 7015. There are variations depending on the rendition of the