Page 30 - Curriculum Visions Dynamic Book

 Ganymede in true colour.
core The central region of a body.
crater A deep bowl-shaped depression in the surface of a body formed by the high- speed impact of another, smaller body.
density A measure of the amount of matter in a space.
latitude Angular distance north or south of the equator, measured through 90°.
Ganmede
Ganymede, the third moon from Jupiter, is also the largest. It is bigger than the planets Mercury and Pluto, and bigger than Saturn’s largest moon, Titan.
It is about 5,260 km across and orbits Jupiter at a distance of about 1.1 million kilometres. It has quite a low density—about 1.7 g/cm3—which suggests it may be about half water and half rock. From this point of view it is similar to Callisto. However, unlike Callisto, Ganymede was big enough to generate its own central source of
heat, so that it became differentiated into a core of rock surrounded by water, with a deep “crust” of ice. Callisto appears to be still a mixture of ice and rock.
Ganymede has a surface that is partly dark and partly light. The darker regions are much more cratered, suggesting that they have been geologically inactive for far longer than the light regions have. The craters are areas of very low relief when compared, for example, with the craters on Earth’s Moon. That may be due to the fact that the ice-rich rims of craters subside under their own weight.
 In this global view of Ganymede’s trailing side in enhanced colour you can see frosty polar caps in addition to bright, grooved land and older, dark, furrowed areas.
The violet hues at the poles may
be the result of small particles of frost, which would scatter more light at shorter wavelengths (the violet end of the spectrum).
Compared to Earth’s polar caps, Ganymede’s polar landscape is extensive, with frost on Ganymede reaching latitudes as low as 40° on average and 25° at some locations.
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