Education and
Public Engagement
at the Lunar and Planetary Institute
Explore! Marvel Moon

Moon's Long History: Impact Paintings


Pairs of children model how scientists use craters to determine the ages of lunar surface. One child keeps time while the other creates a painting for the other to interpret. Cotton balls coated in different colors of paint are thrown at paper to simulate asteroids striking the lunar surface over time. The children take turns in the time-keeping/painting roles to decipher a mystery: In what order did the "impacts" occur? Which painting has more "impacts"? They learn that scientists can estimate the age of a lunar surface by counting its craters — much like counting candles on a birthday cake!

What's the Point?


The following materials are for one Moon's Long History: Impact Paintings activity set and will serve approximately 10 children working in teams of two.

For each child:

For each team of two children:

For the facilitator:



Described in the children's guide.

Facilitator's Note: The children will take turns in the roles of "lunar scientist" and "impactor" to each create two paintings.

The "impactor" creates the first painting over 15 seconds by throwing three cotton balls, each coated ina different color, at the paper for 5 seconds. Encourage the children to reuse the cotton balls, coating them liberally before each toss, like a stamp. The paint should create splatter patterns. The "lunar scientist" will later determine which color was thrown for the first 5 seconds.

Cotton balls are coated with paint
and thrown at a
large sheet of
butcher paper.

The first color is thrown for
5 seconds.

A different color
is thrown on top
of that for
an additional
5 seconds.

The final color is easily seen on top
of the others.

The "impactor" creates a second painting by repeating the process with fresh paper (and additional paint), but throws each color for 20 seconds:

In their comic books, the children will consider their results and use them to determine which of two lunar surfaces is older:

G:\Explore\Marvel Moon\Graphics\oldMoonSurface.gif

The 1-minute painting is more heavily "cratered," like this image of a heavily cratered, ancient surface on the Moon.

G:\Explore\Marvel Moon\Graphics\youngMoonSurface.jpg

The 15-second painting is less "cratered," like this image of a smoother, younger surface on the Moon.



Once they have completed the experiment, the children should understand that craters can be interpreted like candles on a birthday cake: the more you have, the older you are! Scientists count craters to determine how old a lunar surface is.

Young craters have crisp rims and lie on top of other craters. Older craters have softer rims and their ejecta and rays may be covered with fresh craters. The oldest surfaces have many, many craters while fresh surfaces — like the maria, which were more recently formed as lava dried — have few craters. Using these clues, scientists determine when impacts occurred and how old the underlying surface is.

A Little Background for the Facilitator

The Moon is covered with circular patches. Some of these are huge, covering more area than the state of Texas. Some are miniscule, smaller than the tip of a pin. All are caused by the innumerable meteoroids and comets bashing into the surface of the Moon over its 4.5-billion-year lifetime. The large ones you can see from your backyard were created when large meteoroids — asteroids — or comets impacted the Moon. Smaller ones were made by smaller meteoroids. Impactors come in all sizes, and they create circular depressions — craters — of all sizes. The Moon has no atmosphere, so there is no wind, and there is no flowing water on the Moon. Even the most ancient craters are preserved — although they may be covered by other craters and the debris from impacts!

Scientists determine the relative ages of cratered surfaces, such as those on the Moon, by counting craters! The more craters a surface has, the older it is — just like the more candles you have on your birthday cake, the older you are. Scientists also use the same observations the children did — superposition and crosscutting of features — to determine which crater happened first, second, third, and so on. The Lunar Reconnaissance Orbiter, which is currently orbiting the Moon, is sending back high-resolution photographs of the lunar surface. Scientists use these images, and images from other lunar orbiters, to understand which areas of the Moon formed as part of its original crust and the relative ages of younger surfaces.

While craters allow scientists to determine the relative ages of surfaces on the Moon, the Apollo astronauts brought back rock samples that scientists radiometrically dated to determine the absolute ages. These samples come from only six places on the Moon's surface; lunar researchers now know the absolute ages of the basins in these places. With these specific sample ages, the scientists can extrapolate across the lunar surface. In this way they can determine the ages of other features and they can calibrate the ages of surfaces they dated by crater counting.