Creating Ceres Craters
For all my science students, 4th graders through 8th graders, learning about our solar system is one of the most exciting topics they study.
Last year, many of my students were surprised to find two new additions to our solar system. One of these new additions, dwarf planet Ceres, was of particular interest to many students. They thought the Asteroid Belt was filled with small rocks and boulders. Now, there’s a dwarf planet in there. Plus, it’s weird looking.
When Ceres was discovered in 1801, it was classified as a planet. However, it wasn’t long before more and more objects were detected in the same general area between Mars and Jupiter. Ceres was the biggest object noted, but it was still only 590 miles in diameter. With all these boulders being discovered, scientists decided they all couldn’t be classified as planets. It was decided that the larger objects would be called asteroids and the area they were found in would be named the Asteroid Belt. Ceres was renamed an asteroid and stayed that way up until 2006 when it was officially designated a dwarf planet. Ceres has the distinction of being the only object in our solar system to have been named a planet, an asteroid, and a dwarf planet.
Ceres has not had an easy existence. There are millions of boulders in the Asteroid Belt, all tumbling this way and that. Ceres has been bombarded. As a result, its surface is heavily cratered.
Discussing the craters with my older elementary and middle school science students leads easily into an exploration of teams creating their own Ceres craters. They’ll identify the factors affecting the appearance of impact craters, and the material ejected from the impact site, as well as the size and velocity of the impacter.
Teams use cardboard boxes about 40 cm square and about 7-8 cm high. Each cardboard box is filled about three-quarters full of all-purpose flour. The flour is leveled, and then the top is dusted lightly with dry tempera paint. I use a color that contrasts with the flour for the most striking results. Spreading newspapers under the boxes makes clean up much easier.
As impacters, teams can use marbles and ball bearings of about the same size, as well as golf balls. Teams drop these from a series of heights onto a prepared "Ceres surface." Using impacters of different mass dropped from the same height allows students to study the relationship of the mass of the impacter to crater size. Dropping impacters from different heights allows students to study the relationship of velocity of the impacter to crater size.
The teams agree beforehand on the method they will use to "smooth" and resurface the flour between impacts. The flour should not be packed down. Shaking or tilting the boxes back and forth produces a smooth surface. They reapply a fresh dusting of dry tempera paint after each experiment. Be sure to remind everyone that better experimental control is achieved with consistent handling of the materials. For instance, cratering results may vary if the material is packed down for some trials and not for others.
Allow some practice time for dropping marbles and resurfacing the materials in the boxes before students actually begin recording data.
Be sure to have all teams record each experiment. You may want them to graph height and size of impact craters as well as type of impacters used. Be sure to have them draw a detailed picture of one of their craters. After all experimenting is done, ask teams to share their results.
New questions may come out of these debriefing discussions, which in turn will lead to new experiments. Allow students the opportunity to continue to explore cratering, if possible.
By the time students finish this activity, they know what Ceres has gone through as a dwarf planet residing in the Asteroid Belt. About this time you may want to ask them if they think craters on the Moon were formed the same way. Show them photos of Moon craters and compare the pictures to what their cratering looks like.