~ LPI Education/Public Engagement Science Activities ~

MAKING REGOLITH

This activity 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.

Overview —

Participants drop impactors onto layers of graham crackers! The process models how impacts throughout the Moon's history have broken rocks down into a mixture of dust, rocks, and boulders that covers the lunar surface.

WHAT’STHE POINT?

  • The Moon's surface is pulverized by ongoing impacts, which have formed a very fine, dusty lunar "soil" — regolith.
  • Models — such as those the children are using here — can be tools for understanding the natural world

MATERIALS—

  • 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

ACTIVITY —

1) As a single group invite the children to think about different ways regolith can form on Earth:

  • 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?

2) 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?

3) 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.

FACILITATOR BACKGROUND INFORMATION

What is regolith?

You don’t notice it from the surface of the Earth, but the Moon’s surface is covered in a fine, loose material called regolith. Lunar regolith is formed by the weathering of rocks that make up the Moon’s crust. Because the Moon lacks an atmosphere, water and wind are not present to break down rock, as they do on the Earth. However the Moon, like all objects in the solar system, has been bombarded by rocky objects since the formation of the solar system. Over four billion years of impacts has broken up much of the Moon’s original crust to create a global blanket of regolith on the lunar surface. The depth of this regolith varies from region to region but it is found everywhere. Humanity’s first experience with lunar regolith occurred when Neil Armstrong first stepped onto the Moon in 1969 and collected a sample of regolith to bring back to Earth.

Regolith forms on all objects in the solar system with a solid surface, including the Earth. Regolith forms on Earth when bedrock weathers down into smaller, loose particles, from water, wind, and sometimes (though quite rare) meteorite impacts.

A Word on Words. . .

The term "soil" may be used in this activity because children are familiar with "soil." However, "regolith" is a more appropriate term.

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").

is managed by Universities Space Research Association on behalf of NASA