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Roger Weller, geology instructor

Tamara Diffey

Physical Geology

Fall 2006 

What is Astrogeology?
Astrogeology is like most of the earth sciences but is the study of other bodies within our solar system. It can be referred to as planetary geology, exogeology, or xenogeology. Within Astrogeology there are names for each one of the studies of the planets Heliology is the study of the Sun, Hermeology is for Mercury, Cytherology is for Venus, Selenology is the study of the Moon, Areology is the study of Mars, Zenology is the study of Jupiter, Kronology is the study of Saturn, Uranology is the study of Uranus, and Hedeology is the study of Pluto.

               How strange it appears that there could be a use for geology in astronomy but it would appear so. For years people have assumed that the correlation between these to arts of study would never be put together but that was quickly changed when a local geologist to this area began to show the world just how valuable geology could be to the world of astronomy. The use of geology in astronomy is more commonly referred to as either astrogeology or exogeology.


For educational purposes only
Topographical view of Olympus Mons

                It has been proven that at one point in time a large meteorite has impacted the earth which is probably the reason all the dinosaurs died off. Yet the material that the meteorite was made up of was not that much different then the basic material of the Earth.

For educational purposes only
Anatomy of an Impact

                 The first major discovery that meteorites were made of the same type of materials that are found on Earth was done by Eugene Shoemaker who is credited with the creation of astrogeology as a science, Shoemaker's work on what meteorites are comprised of and how common they are to striking planets. His first study was done on the Barringer Meteor Crater near Winslow, Arizona. The findings that the crater was created from a meteorite impact and not large volcanic explosions which was the widely accepted theory at that time.   


For educational purposes only
Barringer Meteor Crater

                The difference in a meteorite impact and an extinct volcanic eruption is detected in the rocks that are found near the edges while a geologist would expect to find the oldest rocks being the furthest out coming in a layered pattern. With a meteorite impact the rocks can be completely mixed up having some of the new rocks being up close to the edge of the crater and older rock sitting in the middle because of how it broke up upon the impact.

                     Earth is the only planet to have both earthquakes (tectonic forces) and rain to wash away natural minerals. Evidence is often lost to the natural process on the Earth which we will never be able to recover but the hope is to begin more study on other planets in the solar system to better understand the effects of asteroids impacting the earth.

For educational purposes only
Impacts on the Moon
                    Without being able to study an impact crater up close most astrogeologists are left to study them from telescopic photos. The most famous one being the comet Shoemaker-Levy 9, which collided with Jupiter in 1994 giving scientist there first glimpse at what might have been under the thick gassy layers of the troposphere. This was a complete comet at one time but they gravity of Jupiter which it had been orbiting pulled it apart 2 years earlier. It was broken into about 23 different pieces striking Jupiter between July 16 and July 22. Some of the impacts were brighter then the Giant Red Spot.

For educational purposes only
Shoemaker-Levy 9 fireball impacts

            Through the study of Venus surface features has shown us that it had active volcanoes at one time and possible still has active volcanoes. The use of satellites and our better knowledge of what the atmosphere is comprised of have allowed scientists to study the planet more closely. What was once believed to be massive amount of meteorite impacts is now known to be volcanoes.

For educational purposes only
Volcano's on the surface of Venus

                Mercury was believed to have been heavily cratered and was soon found to have a large amount of impacts but also had volcanic filling that does not appeared to have occurred for a while. It appears to be just like the moon just with more impacts.

For educational purposes only
Impact craters with volcanic filling

More information on this topic can be found at:
Study Sphere
Museum of Astrogeology
USGS Astrogeology Research Program
USGS Astrogeolgy

More information on the Shoemaker space craft that landed on Eros:
The Faces of Eros