Geology Reference
In-Depth Information
Figure 8.4. Modeled interiors of the Galilean satellites: Io and Europa are composed mostly of silicate materials; Ganymede and Callisto are
mixtures of rocky materials, liquid water, and water ice. Europa has an outer shell of H
2
O, the surface of which is frozen. Liquid saltwater is
likely present on Europa, Ganymede and Callisto, as suggested by the behavior of the Jupiter-induced magnetic
fields. Scale bars indicate the
diameters of Mercury and Earth
'
s Moon.
(a)
(b)
Figure 8.5. (a) The discovery of
active volcanoes outside Earth
was made through analysis of this
Voyager 1 image which shows
this 260 km high explosive plume
(upper left) from the volcano
subsequently named Pele. The
bright spot on the terminator is
the eruptive plume from the
volcano, Loki (NASA PIA00379).
(b) A view of Io showing the anti-
jovian hemisphere (Galileo NASA
PIA00583).
The study of high-resolution images shows that almost
all of the black areas on Io are either the
floors of volcanic
calderas or relatively recent lava flows. Moreover, the
temperatures of many of the dark deposits exceed the
boiling point of sulfur, and they are thought to represent
the eruptions of silicate magmas.
With these observations in mind, Io is seen as a color
kaleidoscope that is constantly changing as new lava
