Investigating Planets
Going Further

Craters, Craters, and More Craters!

Introduction: Impact craters have been found on (almost) every solid surface we have seen so far, from Mercury to Neptune's moons, and even on comet nuclei from the Kuiper Belt and beyond. Consequently, planetary geologists recognize impact cratering as one most important geological processes operating in the Solar System. Cratering seems like a pretty simple process: one object slams into another to form a hole and throw some stuff around. But are impact craters the same on all the moons and planets? Some objects have atmospheres while some do not. Some surfaces are made of rocks, while others are made of ice. Some surfaces may have liquids in or on them while other are completely dry. Some surfaces have very low gravity, and some have fairly high gravity. Can astronomers see any differences in fresh craters on different planets and moons that may be the result of different conditions at the time of impact?

Directions:
Select six or eight planets and moons with different surface condition, like Venus (thick atmosphere, rocky surface), Mars (thin atmosphere, rocky surface), the Moon (rocky surface, no atmosphere), Ganymede (ice surface, no atmosphere), Titan (icy surface, thick atmosphere), Phobos or Eros (rocky surface, no atmosphere, very small in size), Wild2 nucleus (ice surface, no atmosphere, small size), etc. Create a table with all the characteristics of each object that might affect cratering on its surface.

Look at several images of each of your selected objects looking for fresh craters. "Fresh" is somewhat subjective, but fresh craters usually look sharp and crisp, and have recognizable ejecta blankets, usually lighter or darker than the surrounding surface, like Tycho or Copernicus on the Moon. Select 2 or 3 images for each object showing representative fresh craters on each.

Good sources of planetary images you can use:

National Space Science Data Center (good place for Mercury and Venus, the asteroids, and the moons of Uranus and Neptune.):
http://nssdc.gsfc.nasa.gov/image/ click on Catalog of Spacebourne Imaging and select objects of interest.

US Geological survey map-a-Planet:
http://pdsmaps.wr.usgs.gov/ Select a planet or moon. Best for overall view and large features.

Views of the Solar System (an individual's site):
http://www.solarviews.com/ Click on Photo Library.

Mars:
http://marsprogram.jpl.nasa.gov/index.html Click on Multimedia, then Mars Images, and take your pick by subject.

More Mars:
http://www.msss.com/ Click on Mars Images at Malin…. Scroll down to Images by Subject, and take your pick.

Jupiter Satellites:
http://galileo.jpl.nasa.gov/gallery/index.cfm Click on the satellite of choice.

Saturn Satellites:
http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm Select satellite of interest in "Raw Images" pull-down menu and click Go.

Your Report:
1) Create an "Impact Crater Gallery" from your selected images. Look for similarities and differences between the craters on each body (including size), and describe what you found. Try to correlate any differences in crater morphology (appearance) with differences in surface conditions (this may take a little searching for more information about each object). Make a list of different surface conditions that seem to affect the cratering process, and which do not. Create a poster or Powerpoint to display your images, observations, and conclusions.

2) Repeat this project looking at another common planetary feature, such as volcanoes or tectonic cracks and canyons.