Cosmorphology: Creating forms thru geologic and artistic processes
Mayterm 2012 - May 3
Goals for today:
- Learn about the geologic landforms on outer planet satellites
- Learn about Io's geologic history
- Present and discuss several planetary images
- Before class, read:
- Additional recommended reading (see the instructor to borrow):
- For more information about Io, see: Galileo's closest look at Io
by John Spencer. Sky & Telescope May 2001 p 40-46.
- For a more personal look at Io, see: Io and I by John Spencer,
chapter 6 in "Our Worlds" by S. Alan Stern.
- For more on volcanoes, see: The Ground Melts, chapter 13 of Pale
Blue Dot by Carl Sagan.
- For more about the Voyager spacecraft and its discoveries, see:
The Triumph of Voyager, chapter 6 of Pale Blue Dot by Carl Sagan.
- For more about Saturn's moons, see: Among the Moons of Saturn,
chapter 7 of Pale Blue Dot by Carl Sagan.
- For an introduction to Io and more art, see: pages 136-147, Io: A
world turning inside out in "The Grand Tour: A Traveler's Guide to the
Solar System" by Ron Miller and William K. Hartmann.
- Pick at least 4 spacecraft images (at least one from Io and one from another outer solar system satellite), be prepared to present the images and discuss what geologic features are shown, how they formed, and why the forms are interesting to you artistically.
- Pick at least one piece of art (preferably Monica's) inspired by geologic forms. Be prepared to describe the geology depicted in the image.
- E-mail all chosen images to the instructors by 2 pm on Thursday, April 30.
There are at least 125 satellites (moons) in the outer solar system.
While the major planets of the outer solar system (Jupiter, Saturn, Uranus, and Neptune) are very
different places from the inner, terrestrial planets (Mercury, Venus, Earth, and Mars), several of the
moons of those planets have solid surfaces and geology not unlike that
on terrestrial worlds. The major processes of impact cratering,
volcanism, tectonics, and erosion occur on these moons. However, the
surface materials involved in these processes can be completely
different. In the cold of the outer solar system, substances that on
Earth are liquids or gases, are as hard a rocks and can make up the
bedrock of these moons.
Small, Medium, and Large Moons
Generally speaking, moons of the outer solar system can be dived into
three groups: small moons are those less than about 300 km in
diameter, medium moons range from 300 to 1,500 km in diameter, and
large moons are greater than 1,500 km in diameter. Most of the small
moon are dead worlds with little to no evidence of internal geologic
activity. They do not have enough mass for gravity to force them into
a spherical shape, so they generally resemble potatoes. They are so
small and difficult to find that many have only recently been
discovered and there are likely many more yet to be found.
The medium and large moons (see figure) are planetlike in almost all
ways. They are generally spherical and have features on their surfaces
created by both active and external geologic processes. Some have
atmospheres and some have hot interiors that cause ongoing geologic
activity. If you think about the role of planetary size in the
geology of the terrestrial worlds, you might expect all of the outer
planet moons to be geologically dead. After all, only two of the
moons are even as large as Mercury, and Mercury has been geologically
dead for more than 3 billion years. There are two major factors that
can explain how the moons can be more geologically active than larger
bodies. First, tidal
heating is an additional form of internal energy that we have not
yet discussed. Secondly, the outer planet moons tend to be made from
more volatile substances (those that are normally liquids or gases on
earth) that can undergo geological change at much lower temperatures
A tour of some moons
Io is the most
unique of the outer solar system moons. it is the most similar to the
terrestrial planets because it is composed of silicate-based rock.
The other three Galilean satellites of Jupiter, Europa, Ganymede, and Callisto, are
composed mostly of water ice. The four Galileo satellites are large
and the remainder of Jupiter's moons are small, with little
interesting geology. Saturn has one large moon, Titan, the only moon
with a substantial atmosphere. Many other interesting, medium-sized,
moons orbit Saturn, including Enceladus, Rhea, Dione, Tethys, Mimas, and Iapetus. All moons
of Saturn, Uranus, and Neptune, are made primarily of ices like water
ice and carbon dioxide ice (dry ice). Miranda is the most
interesting moon of Uranus, while Triton is the
largest and most geologically active moon of Neptune.