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Origins: Earth is Born

Classroom Activities


The Hunt for Micrometeorites

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Objective
To collect and identify micrometeorites from space.

Materials for teacher
  • razor blade or modeling knife
  • small plastic bags to store prepared slides
  • 4 single-ply cereal boxes
  • 4 plastic sandwich bags
  • various-sized rocks (for weighting down collector)
Materials for students
  • 1 light-colored shower liner
  • 1 rigid plastic wading pool, about 1.5 meters in diameter (optional)
  • duct tape (optional)
  • 4 coffee cans (10 cm diameter;11.5 oz.) with bottom end cut out and plastic lids modified per instructions
  • 4 junior size basket-style coffee filters (round base should be about 7 cm)
  • 4 cereal box halves
  • 16 microscope slides (2.5 cm x 7.5 cm)
  • masking tape
Materials for each team
  • copy of the "The Hunt for Micrometeorites" student handout (PDF or HTML)
  • copy of the "Identifying Sky Dust" student handout (PDF or HTML)
  • spray bottle with trigger
  • 1 cereal box half
  • 4 microscope slides taped to cereal box half
  • white glue, thinned 50 percent with water
  • large plastic bag for storage
  • microscope, with low (100x) and high (400x) power lenses, or stereomicroscope
  • table lamp
  • scissors

Procedure
  1. Some scientists estimate that about 30,000 to 90,000 metric tons of space dust and micrometeorites strike Earth yearly, mostly in the form of particles less than a millimeter in size. These are remnants of the time when the solar system formed about 4.6 billion years ago. In this activity, four student teams will collect and identify sky dust over an eight-day period. (To shorten the activity time period, you can increase the number of collectors or decrease the number of times a single collector is deployed. Note, however, that the more samples that are collected, the higher the probability of students finding a micrometeorite.)

  2. Prior to class:

    • rinse the shower liner (to wash away any contamination)

    • hang it to dry vertically (to minimize dust contamination)

    • store it in a plastic bag (to protect it from contamination)

    • cut each of the four empty cereal boxes in half lengthwise (four halves will be used for slide mounts, four halves will be used as the base on which students will cut the wet coffee filter)

    • cut the bottom end from the four coffee cans and then cut the center from the plastic can covers, leaving the lip and a half-centimeter rim

    • fill the plastic bags with rocks and seal them (these will hold down the collector)

  3. Assign students to make the filter assemblies and slide mounts (see illustrations below). Alternately, you can construct these for students.

    Filter: Filter devices can be made by carefully folding a coffee filter evenly over the top of the can and securing it with the modified plastic cover. Four filter devices should be made.

    Slides: Place four microscope slides side-by-side on a piece of thin cardboard and secure them with masking tape placed perpendicularly across both ends of the slides. There should be no space between the slides. Four sets of mounts should be made.

  4. Review the instructions on the "The Hunt for Micrometeorites" student handout. Organize students into four teams. Provide each team with a copy of the handout and review the instructions with students. Tell students that each team will take turns using the collector (light- colored shower liner) with their filter device for a 48-hour period.

  5. For the first round of collecting, have one of the teams place the collector outside in an open location such as the middle of a lawn or open field (if putting the collector in a plastic pool, use duct tape to secure the four corners). Avoid areas that are exposed to gusty winds, (such as building corners) and contamination from sources (such as falling tree leaves and road spatter). Avoid rainy days. Time of day is unimportant.

  6. Leave the collector out for 48 hours. If high winds or rain are forecast, temporarily move the collector inside. Store the collector by folding it in half (if using pool) or placing it in the plastic bag so that no dust settles on it. Have students look at the collector after 24 hours; if detritus is visible, students can collect the particulate matter at that time.

  7. Provide the first team with a set of collection materials and have team members use the retrieval method outlined in their handouts to collect any particulate matter that has fallen into the collector. If the shower liner is taped to a plastic wading pool, make sure that students do not shake the sheet as they carefully cut the duct tape securing the shower liner to the pool.

  8. Have the first team prepare its slides, making sure that team members only very thinly coat their slides with the watered-down glue. If too much glue is used, it will impart a gloss that makes micrometeorite identification more difficult.

  9. After the slides have dried, use a razor blade or modeling knife to separate them by cutting through the filter material. Choose and store in a plastic bag the slides that have the most particulate matter (not all the slides will have particulate matter on them; four slides are used to allow for a margin of error for students placing the filter on top of them). Repeat the collection procedure with all of the teams.

  10. Once all the teams have retrieved particles from the collector, have students view their findings. If using a compound microscope, have students position a table lamp slightly above the microscope stage. What do students see on their slides? How many different kinds of particles do they see? Have students record the particles they see on their "Identifying Sky Dust" student handout. Work with students to identify as much as possible on their slides. (See Activity Answer for a list of Web sites that contain photos of micrometeorites and other particulate matter that may be found.) Where do students think each of the identifiable particles came from?

  11. As an extension, have students research the origins of the solar system's asteroids and meteorites and write a one-page summary describing the differences between them, where they come from, how they are studied, and what information they can reveal about the universe.


Related Activities

Mineral Identification
www.pacsci.org/origins/
Identify minerals and consider what information they can reveal about the planet from which they came.

Origins
www.amnh.org/education/resources/programs/origins/earth.php
Learn how Earth was born and how meteorites are found in this American Museum of Natural History site that offers articles and student materials related to NOVA's "Earth Is Born" program.


Using a Plastic Wading Pool
Although not required for this activity, a plastic wading pool is recommended. The pool will prevent the shower liner from flapping in the wind and help keep students from accidentally stepping on the liner. A pool will also allow the collector to remain relatively undisturbed (flapped or shaken) fit needs to be moved indoors because of high winds or a rain storm.

Finished Filter

Finished filter

Taped Slides

Taped slides

For additional setup photographs, see www.pbs.org/nova/teachers/activities/3111_origins_03.html


Activity Answer

While most of the material students collect likely will be terrestrial sky dust, it is possible that students may find one micrometeorite in the collector each night. If students do not find any micrometeorites, you may want to lengthen the collection period or try a different venue. See the following Web sites for photos of micrometeorites and other sky dust:

www.skydust.org/
physicsweb.org/article/news/2/5/12#news-2-17-4-1
www.crrel.usace.army.mil/research/projects/Antarctic/epww.htm

Here are some items that have been found by U.S. teams participating in the National Aeolian Detritus Project, a pilot National Science Foundation project to collect and identify sky dust:

  • Micrometeorites
    These can be composed of rock, metal (nickel and iron), or both. The majority of the micrometeorites are made of rock, although these are more difficult to identify than metal micrometeorites, which look small, shiny, etched, black, and more or less round. Metal micro- meteorites will respond to magnets. Although micrometeorites come in a range of sizes (from about 10 microns to 500 microns), the smaller sizes are more common.

  • Carbon balls
    Similar to micrometeorites except that they are dull black and lumpy. Formed when a commercial boiler uses steam to dislodge carbon buildup.

  • Pollen
    Almost always present in various shapes and sizes. Find U.S. regional pollen season information at www.aaaai.org/nab/index. cfm?p=uspollen_seasons

  • Insect parts
    Sometimes parts of insects will show up in collectors. For example, ant wings left from spring mating flights.

  • Whole insects
    Gypsy moth instars (young form) show up in the collectors before their presence is detected by other means.

  • Mineral fractions
    Unusual amounts of illite, a kind of clay particle, were detected in New England collectors two weeks after a large dust storm in Mongolia. The actual arrival time matched the arrival time predicted by computer models.

  • Local oddities
    A team in Massachusetts found "Christmas trees"—clumps of small splinters with little balls at their tips. The team thought they might be a new form of micro- meteorite when they discovered that a magnet attracted them. Careful checking revealed that the collector was near a body shop and that the "Christmas trees" were partially oxidized steel grindings. Another team found long tubes running all over a filter. They turned out to be hyphae, the vegetative body of a fungus that grew on the filter after it had been processed and left damp for too long.


Links and Books

Web Sites

NOVA Web Site—Origins
www.pbs.org/nova/origins/
In this companion Web site to the program, find out how life could have started and why water is needed for life; read about the latest discoveries in origins research; use raw data to assemble the famous Eagle Nebula image; insert your own values into the Drake Equation; decode cosmic spectra; and more.

Age of the Earth
pubs.usgs.gov/gip/geotime/age.html
Explains radiometric dating methods used by scientists to estimate the age of Earth.

Exploring Meteorite Mysteries
spacelink.nasa.gov/Instructional.Materials/NASA.Educational
.Products/Exploring.Meteorite.Mysteries/

Provides information and activities related to meteorites and their origins from such places as Mars, asteroids, and the moon.

Magnetic Field of the Earth
hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html
Examines the Dynamo Effect and its relevance to the formation of Earth's magnetic field.

National Aeolian Detritus Project
www.skydust.org/
Details a project in which students discover micrometeorites and other materials by collecting and identifying sky dust.

The Origin of the Moon
http://www.onlineuniversity.net/earth-science/origin-of-the-moon/
Explores in detail the leading theory of how the moon formed, including factors supporting the theory and its development.


Books

Ball, Phillip. Life's Matrix: A Biography of Water. New York: Farrar, Straus and Giroux, 1999.
Tells of the possible origins of water—its history, pervasiveness and potential presence on other planets.

Marsh, Carole. Asteroids, Comets, and Meteors. New York: Twenty-First Century Books, 1996.
Compares asteroids, comets, and meteors and provides a range of general information on the solar system, the galaxy, and the universe.


Standards

The "The Hunt for Micrometeorites" activity aligns with the following National Science Education Standards:

Grades 5-8

Earth and Space Science

Science Standard D:
Earth and Space Science

Earth in the solar system:

  • The Earth is the third planet from the sun in a system that includes the moon, the sun, eight other planets and their moons, and smaller objects, such as asteroids, and comets. The sun, an average star, is the central and largest body in the solar system.


Grades 9-12

Earth and Space Science

Science Standard D:
Earth and Space Science

The origin and evolution of the Earth system:

  • The sun, the Earth, and the rest of the solar system formed from a nebular cloud of dust and gas 4.6 billion years ago. The early Earth was very different from the planet we live on today.


Classroom Activity Author

James Sammons has taught middle and high school science in Rhode Island for 30 years. His teaching practices have been recognized by the National Science Teachers Association, the Soil Conservation Service, and the National Association of Geoscience Teachers.

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