This is a cutaway of Ganymede's interior.
Click on image for full size
Interior of Ganymede
The diagram to the left shows a cutaway of the possible interior structure of Ganymede, based on recent measurements by the Galileo spacecraft. It shows a small core of metal, overlain with some rocky material, overlain still further with ice of various phases. Further measurements by Galileo suggest that, in addition, Ganymede may have a thin, salty-slushy layer near the surface, where electric currents are found. Ice cannot support electric current, but water can. (That is why people don’t put electric appliances into the bathtub!) An instrument on the spacecraft that is sensitive to current measured something that, like on Ganymede, suggested a watery layer was present on Callisto and Europa as well.
When the Galileo spacecraft flew by Ganymede, to everyone's surprise it measured a very strong magnetic field for the first time near any moon! This provides further evidence that Ganymede is not completely frozen, but has a warm iron core. Over its history, Ganymede may have gone through a late period of warming, rather like Mars, and experienced some icy surface tectonism as a result.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
Minerals occur naturally on rocky planets and form the building blocks of rocks. They are non-living, solid, and, like all matter, are made of atoms of elements. There are many different types of minerals...more
The diagram shows possibilities for the interior structure of Europa. There is a core of rocky material buried inside, overlain with ice of various phases. The diagram shows that there may be an ocean...more
When the Galileo spacecraft flew by Ganymede, to everyone's surprise, it measured a very strong magnetic field for the first time near any moon. To generate a magnetic field, there must be conducting material...more
There has been no icy volcanism on Ganymede, but it does seem that there has been a kind of tectonism, or surface motion. Examination of the surface of Ganymede reveals many kinds of faulting and fracture....more
You may wonder how it is that scientists know what the inside of a planet is like. The interior of a moon or planet can be closely determined from spacecraft navigation data when a spacecraft passes by...more
This image shows an example of the grooved terrain of Ganymede. The image clearly shows that some things hit Ganymede and made craters after the grooves were made, because the grooves are underneath the...more
The surface of Ganymede is halfway between that of Callisto and that of Europa. Portions of the crust are of ancient age, while other portions are relatively new. The little white dots shown in this image...more