Geology Reference
In-Depth Information
All four Galilean satellites are differentiated, with the
degree of differentiation being a function of location
with respect to Jupiter. Io is highly differentiated into
core, mantle, and crust, while Callisto appears to be only
partly differentiated. In addition, Europa, Ganymede,
and Callisto appear to have liquid water beneath icy
crusts, as indicated by the behavior of the magnetic
fields
induced in each by Jupiter
'
s magnetic
field. Ganymede
'
s
high-density and molten core probably accounts for the
generation of its own magnetic
field, making it unique
among the moons of the Solar System.
In addition to the four large moons, Jupiter has some 59
regular and irregular (i.e., captured) satellites, plus rings
that are intimately associated with some of the smaller
moons. The Jupiter system (Jupiter itself, its magnetic
field, the moons, and the rings) is a high priority for future
exploration. Although Europa is a central focus because
of its potential for astrobiology, the entire system is of
interest in consideration of the evolution of habitable
worlds. Thus, Io is an end member with its lack of water
and extremely harsh radiation environment, while Callisto
is at the other extreme with abundant water, most of which
is frozen, and its lack of signi
cant interior heating.
Ganymede is somewhat more favorable for potential
habitable zones, with its internal heat and apparent liquid
water at depth, but, in a sort of
“
Goldilocks
”
scenario,
Europa seems to be an ideal candidate for astrobiological
exploration. It generates suf
cient internal heat to fuel
processes that are probably geologically active today
(or certainly were in the recent past), while harboring
liquid water closer to the surface than Ganymede.
Although it, too, is bathed in radiation from Jupiter, hab-
itats would be shielded by ice only a meter or so below the
surface.
Assignments
1.
Briefly explain how internal heating is generated
within Io, Europa, and Ganymede as a consequence
of their orbital geometries.
4.
Discuss why Europa is a high priority for astrobiolog-
ical exploration.
5.
Brie
y outline the differences between tectonic fea-
tures on Europa and those on Callisto.
2.
Contrast the surface ages for Io, Europa, and Callisto
and discuss the probable geologic reasons for the dif-
ferences among the ages for the three moons. Include
the difference between surface ages and ages of sat-
ellite formation.
6.
Describe the primary characteristics of effusive erup-
tions on Io in terms of compositions, styles of lava
emplacement, and general morphology.
3.
Explain the concept of tectonic resurfacing, especially
as related to Ganymede.
