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Image of Jupiter's largest moon, Ganymede
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Dust Around Moon Gives Clues to Planetary Rings
News story originally written on June 17, 1999

With the help of Galileo, scientists have discovered new evidence that may explain planetary rings. We already know the rings are made of dust and ice. However, until now scientists only had guesses as to how the rings actually formed.

Galileo has found small grains of dust that are always bombarding celestial bodies. When the high speed particles hit the surface, they throw pieces of debris up into space. Smaller bodies, such as moons, have a gravity just strong enough to hold the particles in orbit. Eventually, the grains form a ring.

The research was conducted while studying Ganymede, the largest of Jupiter's 15 moons. Using a small metal can, scientists could measure the speeds of the meteoroids when they hit the moon.

Unfortunately, this new study fails to shed any light on the formation of Saturn's rings, which are made of big chunks of ice.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA