A schematic cut-away view of the components of Jupiter's ring system.

Jupiter May Have Engulfed its Early Moons

March 11, 2009 10:29 AM
by Haley A. Lovett
A new theory suggests that Jupiter may have “eaten” its early moons, and that the four large moons we know today are the last survivors.

Is Jupiter a Moon Eater?

Scientists have long been perplexed by the formation of Jupiter’s moons. Models of formation have not been able to account for what happened to the mass of extra debris that would have surrounded Jupiter at the time its moons were formed.

Robin Canup and William Ward of the Southwest Research Institute in Boulder, Colo., think they know what happened. “All the other moons—and there could have been 20 or more—were devoured by the planet in the early days of the solar system,” Canup told NewScientist.

According to Canup and Ward’s report, “Origin of Europa and the Galilean Satellites,” the “gravitational interactions between the satellites and the gas disk lead to inward orbital migration and loss of the satellites to Jupiter.”

NewScientist explains that when the solar system was forming out of a giant debris disc around the sun, gaseous planets such as Jupiter were able to form more quickly than rocky planets such as Earth. Gaseous planets would then have the gravitational pull early on to absorb any orbiting satellites, whereas rocky planets would form slowly and continue to form after the debris disc was gone, so they would not take on mass and pull in satellites as a gaseous planet might.

Background: Galileo and Jupiter’s moons

Today we know about 62 moons orbiting Jupiter, the largest and most well-known being the original four Galilean Satellites: Io, Europa, Ganymede and Callisto.

Jupiter’s four largest moons have long been fascinating to scientists. For example, Io has the most volcanic activity of any object in the solar system, and Europa’s icy surface may be covering a liquid ocean that scientists think could have the potential to contain life.

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