Explore! Marvel Moon

Infant Moon: Moon Mix!


This station investigates the Moon's infancy, 4.5 billion years ago, when the Moon was still probably hot enough from its formation for at least its surface to be melted. Children model how an ocean of molten rock — magma — helped shape the Moon that we see today. Dense materials in the molten mixture sank, while the least dense materials floated to the top and cooled to form the light–colored areas we see on the Moon today. Children create a simple model of this process by mixing household items of different densities in a bottle and allowing to them to settle into separate layers. They decide which materials make the best model for the infant Moon. Children may examine a type of Earth rock (named anorthosite) that is also found on the Moon and that would have been shaped by the processes explored here.

What's the Point?

  • Scientists study the Moon's rocks and surface features to learnhow it formed and changed over its long "lifetime."
  • Heat from the Moon's formation caused itsouter surface, and perhaps the entire Moon, to melt and form an ocean of magma.
  • While the magma ocean cooled (over about 50–100 million years), the different materials inside of it settled out into layers.
  • Materials with low density floated to the top of the ocean and dense materials sank.
  • The less–dense materials cooled to form light grey crust of anorthosite rock, which is still visible on the Moon today as the lighter areas on the Moon — the lunar highlands.
  • The Moon has some of the same types of rocks that are found on Earth. The rocks have certain properties, such as color.
  • Models — such as those the children are using here — can be tools for understanding the natural world.


The following materials are for one Moon Mix! activity set and will serve approximately 10 children working in teams of two to three.

Three sets are recommended for a station:

  • Optional: butcher paper, newspapers, or disposable table cloths for the activity area
  • 5 (8 oz.) unopened, clear plastic water bottles with the labels removed
  • A selection of at least three of the following items that sink in water, each placed in a container: 
    • 1/2 cup (nearly 1/2 pound) small aquarium gravel
    • 1/2 cup buttons
    • 1/2 cup dried navy beans
    • 1/2 cup marbles
    • 1/2 cup sequins
    • Optional: 1 cup pancake syrup in its bottle or a container with a pour spout
  • A selection of at least three of the following items that float in water, each placed in a container:
    • 1/2 cup coffee stirrers (i.e. small straws), cut into ~1/4" sections
    • 1 dry sponge, cut into (~1/4"x1/4") pieces
    • 1/2 cup pony beads (any color)
    • 1/2 cup small Lego® pieces(e.g. "1x1" bricks)
    • 1/2 cup wooden beads
    • Optional: 1/2 cup vegetable oil in its bottle or a container with a pour spout
  • Optional (but recommended): 1 (32–oz.) bottle of light corn syrup
  • 2 clear plastic cups
  • 1 handheld, wire mesh sieve 
  • 1 cup water
  • Optional: scissors
  • Optional: 1 (1–quart) bag for creating coffee stirrer sections
  • 1 funnel
  • Towel for cleaning up spills
  • Optional: wet wipes
  • Optional: pitcher or bucket for collecting unwanted water
  • Optional: 1 sample of Earth anorthosite, ordered from a natural science catalog; an anorthosite hand specimen is available from WARD'S Natural Science
  • Moon Map: Lunar Highlands
  • Infant Moon: Moon Mix! station sign
  • Infant Moon: Moon Mix! children's guide
  • Art materials, such as colored pencils, crayons, and markers

For each child:

For the facilitator:


  • This is a fun, but potentially messy activity! Have a towel handy for cleaning spills.
  • Cover the table with butcher paper, newspapers, or disposable table cloths, if desired.
  • Place a variety of household items that float and that sink in water at the station, but arrange them randomly so that the children may discover for themselves which items sink or float. Set them out in containers such as bowls, cups, or bags. If you offer syrups and oil, set them out in containers with pour spouts and provide wet wipes.
  • Mark the vegetable oil and pancake syrup, if provided, as follows:
    • Oil: Floats in water
    • Syrup: Sinks in water
  • The children may wish to use a liquid other than water to create their models. If possible, provide corn syrup and set out a container, such as a pitcher or bucket, so that they can pour the water out of their bottles.
  • Cut the sponges and coffee stirrers before the program, or set out scissors for the children to create their own.  Cut the coffee stirrers inside of a (1-quart) bag to keep the sections contained.
  • Provide one clear cup, filled with water, for the children to test the different materials — excluding the vegetable oil and pancake syrup — to see which float and which sink. Set the empty cup aside and use it to reset the station after each team.
  • Prepare enough (8 oz.) water bottles for each team to create one by removing each label. (If you would like each child to create a bottle to take home, double the amount of materials provided at the station.)
  • Place the Earth rock sample, art materials, Moon map, and children's guide at the station.
  • Reset the station after each team's experiment by pouring the contents of the clear cup, through the sieve, into the second, empty cup.


Described in the children's guide.

Facilitator's Note: In this activity, the children are using their knowledge of density to model a process that occurred on the early Moon. If necessary, remind them that density is a measure of how much "stuff" (mass) is contained in a certain space (volume). Density refers to how tightly that material is packed together.

Many of the household items listed above behave predictably when placed in water:  for example, the aquarium gravel sinks and the coffee stirrer sections float. Other items may behave in surprising ways! The children use the cup of water to test the materials before creating their Moon Mix! bottles. They determine how they can best create a mixture that separates into three layers.

Moon mix bottles

The best combination of items to model the early Moon's magma ocean is corn syrup, aquarium gravel, and navy beans. (Note that the water bottle should be emptied first; corn syrup is too difficult to distinguish from water to use both liquids as layers, and it is soluble in water.) At first, the navy beans and gravel sink in the corn syrup. After vigorous mixing — the children will need to shake long and hard — the navy beans will slowly float to the top when finally allowed to settle.

Sometimes some of the household materials will get "caught" in the wrong layers of the Moon Mix! bottles. This also happens inside moons and planets!


In building their understanding of the history of events that took place during the formation and early changes to our Moon, the children used a concept familiar to them — that some materials sink and others float — to create a model for themselves. They tested, then selected, one type of item that sank and one type that floated and mixed them together in a bottle of water or corn syrup. The model represents the separation of materials within the Moon's early magma ocean. 

The children should understand that this process of separation helped shape the Moon that we see today. The "infant" Moon (4.5 billion years ago) was still probably hot enough from its formation for at least its surface to be melted. Scientists call this hot, molten mixture of different materials the "magma ocean." Over time, dense materials sank, while the least dense materials floated to the top and cooled to form the lunar crust. We see these least dense materials when we look at the Moon today; they form the light-colored areas we see on the Moon. The darker patches are denser materials that rose to the surface later, during the Moon's "teenage years."

In the children's models, some types of items sank and others floated in water because they have different densities. Aquarium gravel, buttons, dried navy beans, marbles, sequins, or pancake syrup sank because they are more dense water, and coffee stirrer sections, dry sponge, pony beads, small Lego pieces, wooden beads, or vegetable oil floated because they are less dense than water. Sometimes, some of the items got "caught" in the wrong layers. This also happens inside moons and planets. Also like the early Moon's interior, where all of the materials that made up the Moon’s outer layers were mixed together as an ocean of magma, the items in the children's bottles were mixed together. Then the items separated into layers.

Some of the items behaved differently when placed in corn syrup. Dried navy beans are less dense than corn syrup, so they floated (eventually!), while aquarium gravel sank.

The children investigated a type of Earth rock called anorthosite, which they should recognize as similar to those found on the Moon. They located the light-colored regions that we see on the Moon:  the lunar highlands. They should recognize these areas as made up of the light-colored type of rock and connect their formation to the less-dense materials rising to the top of the magma ocean.

Like the children did, scientists investigate the Moon by creating models, as well as by studying Moon rocks and surface features.

A Little Background for the Facilitator

The Moon was hot during its "infancy." It had just formed from the debris left over after a giant impactor struck Earth. As the debris reassembled — accreted — to form our Moon, it heated up. Each impact added material to our growing Moon, but each impact also generated heat. Eventually, heat from thousands and thousands and thousands of impacts caused the surface of the Moon — or perhaps the entire Moon — to melt. Scientists call this deep ocean of molten rock the "magma ocean." The evidence for a magma ocean comes from the observation that the oldest crust, which makes up the outer layer of the Moon, is all made of the same rock type:  a light-colored rock named "anorthosite."

Anorthosite itself is primarily made of a single mineral, called plagioclase feldspar, which contains a lot of aluminum and has a relatively low-density. This mineral floated to the top of the magma ocean, where it cooled to form the Moon's crust. This slow crystallization from magma is the only known way to produce acrust made mostly of one type of mineral. This rock forms the "lunar highlands" which are the brighter, light-colored, heavily cratered regions we see on the Moon today.

Deeper parts of the Moon's crust and mantle include larger amounts of other, heavier, minerals, such as pyroxene and olivine. These denser materials sank out of the magma ocean. Later, during the Moon's "teenage years" of volcanic activity, some of these denser materials re-melted and rose to the surface. These materials make up the dark patches we see on the Moon.

The magma ocean cooled and crystallized over a period of 50–100 million years to form a lunar crust that is, on average, about 42 miles (68 kilometers) thick. The oldest rocks collected by Apollo astronauts are 4.5 billion years old, which is thought to indicate when the Moon’s crust solidified.


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