Deep Impacts in the Classroom

Abstract:
NASA's Deep Impact mission launched in January of 2005 on a six-month mission
to rendezvous with the comet Tempel 1 on July 4, 2005.  Along the way, it
traveled more then 300 million miles at an average velocity of more then
60,000 miles per hour.  Once the satellite caught up to the comet, it
released an 800 lb impactor the size of a refrigerator that
smashed into the comet with enough energy to produce crater the size of a
small building over 100 feet deep; the energy released in the collision
was equivalent to the explosion of 4.8 tons of TNT -- that would have been enough energy
to power your house for a whole month.  Meanwhile, The satellite that dropped the impactor
took pictures of the event, while scientists on Earth observed the
plume of debris with telescopes.  These observations helped determine
the fractional composition of the comet, as well as whether its surface
composition was similar to its composition within.  A thorough understanding
of cometary composition is important because comets are left-over snow balls
from the formation of the planets, and their fractional composition
should mirror the composition of the protoplanetary disk from which the Earth
formed over 4.5 billion years ago.  For more information of the Deep Impact
mission and what was learned, visit:

http://deepimpact.jpl.nasa.gov/home/index.html

We will ``impact" our own ``comet" in the lab and attempt to determine its
composition based on our own first-hand experimental observations.

Materials:
1.)   1 softball or baseball
2.)   4 plastic trays about 30 cm x 30 cm x 7 cm (or 12" x 12" x 4")
3.)   12.5 kg (or ~30 lb) of sand 
4.)   12.5 kg (or ~30 lb) of gravel
5.)   6 kg (or ~15 lb) of crushed water ice (H_2 0)
6.)   2 kg (or ~5 lb) of crushed dry ice (CO_2)
7.)   Some soot
8.)   One cooler or access to a refrigerator
9.)   A balcony, a ladder, or a desk to stand on
10.)  A ruler
11.)  A notebook or white board to record observations

Preparation:
1.) Fill one tray with ~8 kg of sand and smooth the surface.  This tray will
    be called Tray I.
2.) Fill one tray with ~8 kg of gravel and smooth the surface.  This tray will
    be called Tray II.
3.) Fill one tray with ~4 kg of crushed water ice, smooth the surface,
    and put it in the cooler or refrigerator.  This tray will
    be called Tray III.
4.) Fill one tray with the rest of the sand, gravel, crushed water ice, and
    crushed dry ice.  Mix well, smooth the surface, cover the surface
    with the soot, and put it in the cooler or refrigerator.  This tray will
    be called Tray IV -- it is our ``comet" and is of unknown composition (at
    least to the students).
5.) Note that it's best not to prepare the ice trays until shortly
    before the lesson, if possible.

Procedure:
1.) Introductory discussion
2.) Place each tray I-III on the ground, keeping tray IV safely out-of-view
    for the time being
3.) Drop the softball/baseball from the elevated position provided by the
    balcony/ladder/desk into the first tray.  Observe the impact, paying
    special attention to:
    - the amount of material ejected from the tray, and direction in which
      it is ejected
    - the shape and depth of the crater that the ball forms
    - the sound of the impact
    - feel free to smooth over the crater and repeat the experiment
    - record your observations
4.) Repeat the drop and the listed observations for each tray I-III
5.) Summarize your observations.  What material had the deepest crater?
    Which material had the most ejecta?  Concisely describe the sound made
    by each impact.
6.) Bring out the tray IV, which is of ``unknown" composition.  This is our
    comet.
7.) Repeat the instructions given in step 3, and carefully observe the impact.
8.) Use your observations of the impact in tray I-III to surmise the
    composition of the ``unknown" material in tray IV.

Useful Links:
Simulation Movie 1 - http://deepimpact.jpl.nasa.gov/gallery/mpeg-flyby1m.html
Simulation Movie 2 - http://deepimpact.jpl.nasa.gov/gallery/mpeg-flyby1h.html
Real Movie 1 - http://www.nasa.gov/mission_pages/deepimpact/multimedia/070405-HRI-impact.html
Real Movie 2 - http://www.nasa.gov/mission_pages/deepimpact/multimedia/070305-Stream-movie.html
Lab Movie 1 - http://deepimpact.jpl.nasa.gov/gallery/anim4stills.html
Lab Movie 2 - http://www.nasa.gov/mission_pages/deepimpact/multimedia/experiment.html
Lab Movie 3 - http://deepimpact.jpl.nasa.gov/gallery/mpeg3.html
Lab Movie 4 - http://deepimpact.jpl.nasa.gov/gallery/mpeg4.html