Comets created difference in Jupiter's moons

Findings could shed light on our solar system, and planets in general

http://www.msnbc.msn.com/id/35062190/ns/technology_and_science-space/

Each of Jupiter's more than 60 moons has its own unique character, but scientists have often wondered at the striking differences between the surfaces and interiors of two of the gas giant's largest moons, Ganymede and Callisto.

A new study, detailed in the Jan. 24 issue of the journal Nature Geoscience, might have found an explanation for the disparate features of these Galilean moons: Ganymede was pummeled by more and faster comets impacts than its sister moon billions of years ago.

While Ganymede and Callisto are similar in size and both made up of a mixture of ice and rock, data from both the Galileo and Voyager missions show that they sport different looks, both on the inside and outside.