Lunar and Planetary Institute






The Scoop on Moon Dirt
EXPLORE! To the Moon and Beyond with NASA's LRO Mission

The Scoop on Moon Dirt

Overview

In this two-part, 75-minute activity, children ages 8 to 11 compare how soil forms on Earth and the Moon. They examine different soil samples and compare them to lunar "soil" simulant. They explore how water, wind, and impactors help to make soil.

What's the Point?

  • Different soils have different properties (color, texture, composition).
  • Lunar "soil" — regolith — does not have any organic components like Earth soil does.
  • Different soils form from different rock types and under different conditions.
  • Earth's rocks break down (weather) through the action of water and wind (other physical, chemical, or biological weathering mechanisms; for example, root formation, freezing and thawing, or leaching, are not addressed).
  • Lunar "soil" — regolith — forms when impactors strike the Moon's surface and pulverize the rock.

Materials

For the group:

Part A. Examining Soils
For each team of three to four children:

  • Three paper plates
    • Local soil sample 1 (on plate labeled as Sample A)
    • Local soil sample 2 (on plate labeled as Sample B)
    • Lunar soil simulant (on plate labeled as Sample C)
  • Magnifying glass (5 –10x)
  • Magnet
  • Several toothpicks
  • Paper, writing instruments

Part B. Making Regolith
For each team of three to four children:

  • 1 margarine container, filled three-fourths full with sand  and water and frozen
  • Access to a sink with flowing water (can be done with pitchers of water)
  • 2 pieces of dry, brittle bread
  • 1 (2"x2") piece of coarse sandpaper
  • 1 large cardboard box (~2" per side) with high sides
  • 10 –15 graham crackers (enough to cover the bottom of the box with two layers)
  • Fist-sized rock or a (1–lb.) box of baking soda wrapped in aluminum foil

For the facilitator:

Preparation

  • Fill the margarine tubs about three-fourths full with sand; add water to cover the sand and freeze lightly.
  • Collect two very different soil samples from your local area(perhaps from a field, a flower bed, or the area near a stream).
  • Label and prepare the sample plates for each group.

A Word on Words . . .

The term "soil" is being used in this activity because children are familiar with "soil." "Regolith" is a more appropriate term and is introduced later in the activity.

Soil: the unconsolidated (loose) top layer of material on Earth's surface that is made of minerals and, usually, organic matter in which plants grow.

Regolith: a general term for the layer of loose rock material that forms the surface of a planet — including Earth! — and covers the rock. Soil is a type of regolith. Other types of regolith include volcanic ash, materials deposited by a glacier or river, sand dunes, the red rocky surface materials of Mars, and the layer of material on the lunar surface.

Dirt: a term used by small children and gardeners to describe soil; a term used by scientists when they are unimpressed with the qualities of the regolith they are investigating or when they are more interested in the layers of rock beneath the regolith. May also refer to information, often of a negative connotation (e.g., "I have the dirt on you").

Activity

Part A. Examining Soils
1. Invite the children to tell you what they know about dirt or soil.
What is it made of? Where is it found? Are there different types of soils?

Introduce them to the Lunar Reconnaissance Orbiter Mission — LRO — that is currently orbiting the Moon! Some of the instruments onboard are providimg information about properties of lunar soil, such as its color, minerals it may contain, thickness, how compact it is, and if it contains frozen water. The LRO instruments are also helping scientists map the lunar surface, collecting information about how temperatures on the Moon change, and finding out if frozen water exists in deep, dark craters near the polar regions.

Ask the children to share what they know about the Moon. Remind them that the Moon has no water and no atmosphere, in addition to other insights they may share.

2. Divide the children into groups and explain that they will be investigating several different dirt or soil samples. Their job is to describe the characteristics.

  • How might they describe soil? Note their responses. Color, size of materials in the soil, types of materials in the soil.
  • What might a magnifying glass help them determine? More details about what is in the soil.
  • What about a magnet? Whether any of the materials are magnetic.

Let the groups explore the different soil samples. Have them describe what they are finding.

Remind them that they should not taste the samples and that they can use the toothpicks to probe the soil! Scientists examining lunar samples do not handle them; lunar materials are kept under very sterile conditions in the laboratory so that they are not affected by water or particles in Earth's atmosphere. Lunar samples are kept in sealed work boxes that have holes where gloves are attached. Scientists work with the samples using the gloves.

3. Bring the children back to the main group and ask them to share what they observed about each of the three samples; write their responses on poster paper.

  • What were the colors of the different soils?
  • Did some break apart more easily than others?
  • What did they see when they looked under the magnifying glass? Were the sizes of the particles the same or different? How big were they?
  • What happened when the magnet was passed over each sample?
  • What materials made up each of the different soils?
  • Did any of the samples have organic materialmaterial from living things like trees or grass? Share that the term "regolith" can be used for all the samples; regolith means the loose rock material on the surface. Commonly, "soil" is used for samples that contain mineral and organic — plant — material. Which of the samples are soils? Which are regolith?
  • Were any of the soils dry? Wet? Did any have a smell? What did they smell like?
  • What clues do the soils give about how or where they formed? Roots tell us that plants were present where the soil formed; living roots also help to break down soil.
  • Where do the children think the different samples came from? Share that one sample is regolith, like what we find on the Moon — it is not an actual sample of lunar regolith, but very much like one. Can they guess which one? What did they base their hypothesis on?
  • Share the image of the astronaut's bootprints on the Moon. Is there any evidence of lunar "soil"/regolith? What does it look like?

4. After they determine which sample is which, let them know where you collected the samples and which is the lunar regolith simulant. They may wish to reexamine the samples.

  • Why might the sesamples be soooooo different? They formed from different materials.
  • Where does soil — or regolith — come from? The breakdown of rock; the children may need help thinking about this.

5. Have the children think about the different soils around the library or their homes. There are garden beds and top soil where grass grows. There may be other types of soil — either naturally in place, or put there by humans. Each soil has its own characteristics and depends on what kind of rock it formed from and the conditions under which it formed (wet or dry, cold or hot).

Regolith found on the Moon also formed from different rock types. Some have more of one kind of element than others — like aluminum or titanium, if they formed from rocks with these types of elements. Others may contain frozen water in the spaces between particles. Instruments onboard the LRO spacecraft are helping us map the properties of soils on the Moon.

Part B. Making Regolith
Part B has been modified from "Regolith Formation," an activity in Exploring the Moon, A Teacher's Guide with Activities for Earth and Space Sciences, NASA Educational Product EG-1997-10-116 – HQ by J. Taylor and L. Martel.

6. Invite the children to think about different ways regolith can form.

  • What helps to break down rock on Earth? Flowing water, the expansion of freezing water, wind and wind-carried particles, plant roots widening cracks in rocks. The children may think of some of these ideas; the next part of the activity will give them firsthand experience with flowing water and wind.
  • How might formation of regolith on the Moon be different from Earth?

7. Place the children back into their groups. Provide each group with the frozen block of water and sand and ask them to imagine that this is a rock — a sandstone! Have the groups place their "rock" in the dishpan under the faucet and turn the water on at a slow to medium stream. Alternatively, use water poured from a pitcher or bottle.

8. Bring the children back together to discuss what they found.

  • What happens to the rock? The water wears it away.
  • What does this tell us about how water contributes to the breakdown of rocks?
  • Does this happen on Earth? You bet!
  • Is there any flowing water on the Moon's surface? Nope.
  • Does water help form regolith on the Moon? Nope.

9. Now invite the children to explore how wind can break down rocks. Provide each group with a piece of dry, brittle bread and ask them to imagine it is a rock.

  • What happens when their hand — acting like the wind — brushes across the bread? Small crumbs may fall from it.
  • What happens when they rub a piece of sandpaper across the surface? Many more crumbs break away from the surface!

10. Bring the children back together to discuss what they observed.

  • What process does this represent? Sometimes the wind is strong enough to carry particles of rock. These particles act like the sandpaper when they are blown against rock surfaces.
  • What does this tell us about how wind contributes to the breakdown of rocks?
  • Does this happen on Earth? You bet!
  • Is there any wind blowing on the Moon's surface? Nope; the Moon has no atmosphere, so there is no wind.
  • Does wind help form regolith on the Moon? Nope.

What does make regolith — the lunar "soil?" Do the children have any ideas? Show them the image of the Moon. What are the round shapes on the Moon's surface? How do they form?

11. Divide the children back into groups and provide each group with the container of graham crackers and large rock. The graham crackers are the lunar surface, the rock is a large asteroid! Ask the children to drop the asteroid, from about waist high, into the container.

  • What happens?
  • Have them repeat the process 5 times. What do they observe?
  • Have them repeat the process ~20 more times. What do they observe?

12. Bring the children back together to discuss their observations and thoughts.

  • What process does this represent? Impactors striking the surface of the Moon — or Earth! — breaking down the surface rocks into regolith.
  • What changed from one impact to five to twenty? The graham cracker rocks became more broken and the crumb regolith became thicker and finer.
  • What does this tell us about how impacts by asteroids and comets contribute to the breakdown of rocks?
  • Does this happen on Earth? Yes, but only rarely. Earth's surface is constantly "recycled" by wind and water and other processes, so the evidence of many of these craters has been erased. Earth's atmosphere also helps to protect us from being struck by smaller asteroids; they burn up in our atmosphere, making the beautiful streaks of light — meteors — that we occasionally see.
  • Do impacts occur on the Moon? Yes, also rarely now, but wind and water do not flow on the Moon's surface. Once craters form, they are not altered by other processes unless they get hit by another rock from space! The Moon's surface preserves a record of almost four and a half billion years of impact, after impact, after impact, after impact!
  • Do impacts help form regolith on the Moon? You bet! They are the main process forming lunar regolith.

Conclusion

Revisit with the children what they have learned.

  • How do soils form on Earth?
  • Do these same processes form regolith on the Moon?
  • How does regolith form on the Moon?
  • What will the LRO tell us about lunar "soils?"

Last updated
February 9, 2010

 

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