Ganymede G1 & G2 Encounters - Interior of Ganymede

NOTE: This JPEG image is made available in order to share with the public the excitement of new discoveries being made via the NASA/JPL Galileo spacecraft. Galileo scientists are in the process of calibrating and validating this data. The full digital image necessary for scientific analysis will be released within one year of receipt of this orbit's last data.

This image is available only on the WWW; it is not available in hardcopy or other forms.

Voyager images are used to create a global view of Ganymede. The cut-out reveals the interior structure of this icy moon. This structure consists of four layers based on measurements of Ganymede's gravity field and theoretical analyses using Ganymede's known mass, size and density. Ganymede's surface is rich in water ice and Voyager and Galileo images show features which are evidence of geological and tectonic disruption of the surface in the past. As with the Earth, these geological features reflect forces and processes deep within Ganymede's interior. Based on geochemical and geophysical models, scientists expected Ganymede's interior to either consist of: a) an undifferentiated mixture of rock and ice or b) a differentiated structure with a large lunar sized 'core' of rock and possibly iron overlain by a deep layer of warm soft ice capped by a thin cold rigid ice crust. Galileo's measurement of Ganymede's gravity field during its first and second encounters with the huge moon have basically confirmed the differentiated model and allowed scientists to estimate the size of these layers more accurately. In addition the data strongly suggest that a dense metallic core exists at the center of the rock core. This metallic core suggests a greater degree of heating at sometime in Ganymede's past than had been proposed before and may be the source of Ganymede's magnetic field discovered by Galileo's space physics experiments.

Galileo's primary 24 month mission includes eleven orbits around Jupiter and will provide observations of Jupiter, its moons and its magnetosphere. The Galileo mission is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C. .

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo.

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