Impact craters form whenever an asteroid or comet crashes into the
solid surface of another body. Craters can form on planets, moons,
and even asteroids. The process of
cratering is responsible
for shaping the surfaces of most objects in the Solar System.
Wind and rain on Earth slowly erase craters, so only recent craters or
the very largest craters remain visible as time passes. For example,
Meteor Crater, in northern Arizona, is about 10,000 years old, a blink
of the eye in the history of our planet. On bodies like the Moon or
Mercury that have no air or water, craters can last millions or
billions of years, preserving a record of the pummelling they've
received.
Impacts occur at phenomenal speeds - 5000 times faster than a
dropping rock. The force of the impact is enough to pulverize rock.
But using some basic ingredients, you can study how craters are
formed.
The materials for the crater activity are:
- a basin of some sort, to be filled with flour (examples are a dishpan,
an aluminum roasting pan, a plastic tub, a cardboard box),
- enough flour to fill the basin 3 to 5 inches deep,
- container filled with chocolate milk powder or baking cocoa powder (a large
shaker works well),
- ball bearings, metal nuts, or rocks of several sizes, no larger than a half inch,
- a spoon or magnet to retrieve the ball bearings or rocks
Instructions:
- Fill the basin with flour,
- Sprinkle chocolate or cocoa powder onto the flour in a thin, even layer, darkening
the whole surface,
- Drop (don't throw) the ball bearings or rocks into the basin,
- Compare the craters you make to pictures of the Moon or other bodies in the Solar System,
- Vary these factors and see how they affect the craters:
- Size of object dropped (big rock vs. small rock)
- Height & Speed of drop (the higher the drop the faster the impact!)
- Depth of flour
An important observation to make for each crater is the way the flour
is distributed around the crater on the cocoa. Long streaks are known
as
rays and can be seen in many images of craters,
especially Kepler, Copernicus, and Tycho craters on the Moon.
Pictures of craters are available on various sites on the web:
This page
shows a variety of craters on the Moon, Mars, Venus, and Earth
This page is
an atlas of images of the Moon (lots of images, so be patient)
This picture shows
several craters with rays on the Moon
This picture is a
sharp image of the Full Moon
This picture is a
sharp image of the Far Side of the Moon (the side always pointing away from Earth)
Questions/comments? Contact us at
astro.info@asu.edu