Rocky Rubble Piles
What's the Point?
- 3 hand-sized rocks (about 2in x 3in x 3in)
- about 3 cups of sand
- a large liquid measuring cup (big enough to put one of the rocks inside)
- a freezer (best) or cooler filled with ice
- aluminum foil
- a marker that will write on foil
- Background information:
- Invite the children to share what they know about asteroids.
Facilitator’s Note: : If a child or other participant’s statements are incorrect, consider asking additional questions to the group that allow them to share what they know, rather than immediately correcting them. As much as possible, encourage the children to offer information and to respond to others’ questions, rather than answering them yourself. Use phrases like “What do the rest of you think?” “Do you agree with ____?” “Do you have any additional ideas?”
- What are asteroids? (Asteroids are rocky objects, smaller than planets, orbiting our Sun.)
- What are asteroids made of? (Asteroids are primarily rock and dust, and some also have ice. Some asteroids appear to be solid rock, and others are made of piles of rock and dust.)
- Could they be dangerous? (Yes, if they hit the Earth.)
- Share that we are studying asteroids so that we can safely move them away from Earth’s orbit.
- Share that NASA’s missions and observatories are studying asteroids and collecting information about them.
- Are there different tools we can use to study asteroids? (We can use telescopes and can send robotic spacecraft to asteroids.)
- How can we study the inside of an asteroid? (No instruments can "see" inside an asteroid. We need to use indirect methods to study asteroid interiors.)
- Why is it important that we know what asteroids are made of? (Our plans to deflect asteroids may work differently, depending on whether they are solid or not.)
- Describe OSIRIS-REx and NEOWISE missions: The OSIRIS-REx mission is studying the asteroid Bennu, and measuring its physical properties, including its internal structure. OSIRIS-REx will return a sample of Bennu’s surface to the Earth in 2023 for study. The NEOWISE project is a telescope orbiting the Earth that is finding warm asteroids by the infrared energy they are emitting into space. Many other telescopes on Earth are also collecting data about asteroids. These missions and observatories can measure sizes, positions, and even temperatures!
- Tell the children that they are going to explore models of asteroids, to understand how we can learn about the insides of asteroids.
- Explain that some of the models are made of sand, and others are made of rock, but they all look similar on the outside.
- How could we tell which ones are made of sand and which are rock? Accept all answers, adding that scientists can’t break open or even touch most asteroids in real life.
- Which warms up faster: a glass filled with small pieces of ice, or a glass filled with a large solid piece of ice? (Smaller pieces of ice warm up faster.) If the children struggle with this, ask which cools off faster from the oven: cupcakes or a single large cake? (Small cupcakes will cool off faster.) Invite the children to share their experiences with cooking (or eating) food that warms up faster or cools off faster. Repeat at the end that a group of smaller pieces will cool off or warm up faster than a larger object.
- How can we determine if our asteroid models are made of lots of small pieces of sand or if they’re made of solid rock? (We can measure how quickly they warm up or cool down.)
- Let the children know that you have frozen the models of asteroids, and they will measure their temperatures over the next 10 minutes as the asteroids warm up.
- Give each child or group of children a Solid or Rubble Notes sheet and pen or pencil, and a laser infrared thermometer.
- Divide the children into groups. Each group will measure at least one asteroid model (or each group could move around and measure all of the asteroid models).
- Tell the children the sizes you recorded for each of the asteroid models, and ask them to write the sizes for each of the models they will measure on their notes sheet.
- Show the children how to take a temperature using the thermometers. If the thermometer uses a laser that could cause eye damage, carefully monitor the children’s uses of it and reiterate that they cannot point it at anyone’s face. If children are mature enough to use the thermometer safely, have them take turns practicing taking the temperature of the tables, windows, and other objects in the room; otherwise, model how the thermometer works by taking and sharing the temperatures of objects in the room for the children.
- Take the asteroid models out of the freezer or cooler and place them on tables.
- Do not let the children pick up or handle the asteroids. (Doing so will affect the temperature measurements.)
- Either invite the children to take turns using the thermometers to take the temperatures of the asteroids every minute or two or take them yourself. Ask the children to record the temperatures of the asteroid models on the Data Sheet. Note: Temperatures will be different on different sides of the “asteroids.” Take the temperatures at the center of the top surface or as close to that point as possible.
- Halt the measurements after 10 minutes or when the asteroids reach room temperature.
- Invite each group to share their data and observations with the others.
Discuss their initial findings:
- Did all of the asteroids warm up at the same rate?
- Did the size of the asteroids make a difference?
- What ideas do they have about why some asteroids warmed up faster than others?
- Now, why do they think some asteroids warmed up faster than others?
- Which asteroid models do they think were made of sand?
Thank the children for their research! Ask whether it was easy to determine which asteroid models were made of rocks and which were made of sand. Ask whether they were surprised by their findings. Invite the children to share how it felt to be conducting research and making discoveries.
Reiterate that scientists are studying the characteristics of asteroids, including determining which ones are likely to be solid and which are likely to be rubble piles, to learn more about our solar system and to help up understand how to defend Earth from asteroids.
Activity Background Information:
This activity serves as a model of how we study planetary objects. Scientists are able to directly observe some of an object's characteristics, such as location in the solar system, size, mass, external composition, and more.