New Map Reveals Geology of Jupiter's Moon Ganymede
A global image mosaic of Jupiter's moon, Ganymede created with images from the Voyager and Galileo missions.
Credit: Wes Patterson

Jupiter's moon Ganymede, the largest moon in the solar system, now has a detailed global map that will help scientists better understand the large, icy satellite.

The map is the product of a seven-year effort and is only the third global geological map ever compiled for a moon in the solar system, after Earth?s moon and Jupiter?s cratered satellite Callisto.

"The map really gives us a more complete understanding of the geological processes that have shaped the moon we see today," said Wes Patterson, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., who led the map effort.

Patterson's team will present the map, created with data images from NASA?s historic Voyager and Galileo missions, on Wednesday at the 2009 European Planetary Science Congress in Potsdam, Germany.

With a diameter of 3,280 miles (5,262 km), Ganymede is the largest moon in the solar system. Larger than both planet Mercury and dwarf planet Pluto, it?s also the only satellite in the solar system known to have its own magnetosphere.

While scientists have crafted several regional geological maps of Ganymede?s surface using Voyager data, Patterson?s team was the first to combine the low-resolution Voyager photos with high-resolution Galileo images to create a global and consistent view of the moon?s geology.

The new map details geologic features that formed and evolved over much of our solar system?s history. These features record evidence of the internal evolution of this large icy satellite, of its dynamical interactions with the other Galilean satellites, and of the evolution of the population of small bodies impacting the surface of the satellite.

"By mapping the entirety of Ganymede?s surface, we can more accurately address scientific questions regarding the formation and evolution of this truly unique moon," Patterson said. "Work done using the map by collaborator Geoff Collins at Wheaton College, for instance, has shown that vast swaths of grooved terrain covering the surface of the satellite formed in a specific sequence. The details of this sequence tell us something about the forces that must have been necessary to form those swaths."

Patterson says scientists can look at Ganymede?s geological history as a ?touchstone? for comparing and contrasting the characteristics and evolution of other large to mid-sized icy satellites. The map will also, he adds, be a reference for exploration of the Jovian system.

NASA and the European Space Agency are currently developing a future voyage: the Europa Jupiter System Mission would include orbiters of Ganymede as well as the icy satellite Europa.

"A primary goal of the next flagship mission to the Jupiter system will be to characterize, in detail, the geophysical, compositional, geological, and external processes that affect icy satellites," Patterson said. "This map will be an invaluable tool in determining how best to address those goals for Ganymede."