1. No category

It is marvelous indeed to watch on television the rings of
Saturn close; and to speculate on what we may yet find at
galaxy’s edge. But in the process, we have lost the human
element; not to mention the high hope of those quaint days
when flight would create “one world.'” Instead of one world,
we have '”star wars”, and a future in which dumb dented
human toys will drift mindlessly about the cosmos long
after our small planet's dead.
Gore Vidal
Arizona State University
AST 111
Introduction to Solar Systems Astronomy
Frank Timmes
fxt.teaching@gmail.edu
cococubed.asu.edu/class_pages/class_planet.shtml
Chapter 11 - Jovian Planets - Learning Goals:
A Wealth of Worlds: Satellites of Ice and Rock
‣What kinds of moons orbit the jovian planets?
‣Why are Jupiter’s Galilean moons so geologically active?
‣What is remarkable about Titan and other major moons of
the outer solar system?
‣Why are small icy moons more geologically active than small
rocky planets?
What kinds of moons orbit the jovians?
We can categorize the more than 100
known moons as small, medium, or
large.
Most of the medium and large moons
probably formed with their planets in the
disks of gas that surrounded their jovian
planets when they were young.
Smaller moons are
often captured
asteroids or
comets.
Why are Jupiter’s Galilean moons so geologically active?
Io is the most volcanically
active object in the solar
system ...
... thanks to an interior kept hot by
tidal heating - which occurs
because Io’s close orbit is made
elliptical by orbital resonances with
other moons.
Europa (and possibly Ganymede) may have a deep, liquid water ocean under
its icy crust also thanks to tidal heating. Callisto is the least geologically
active since it has no tidal heating or orbital resonances.
What is about Titan and other major moons of the outer solar system?
Many medium and large moons show a surprisingly high level of past or
present volcanism or tectonics. Titan has a thick atmosphere and ongoing
erosion.
Triton, which apparently was captured by Neptune, also shows signs of recent
geological activity.
Why are small icy moons more geologically active than small rocky planets?
Ices deform and melt at much lower temperatures than rock, allowing icy
volcanism and tectonics at surprisingly low temperatures. In addition, some
jovian moons have a heat source - tidal heating - that is not important for the
terrestrial worlds.