Explore! Jupiter's Family Secrets

Investigating the Insides


Investigating the Insides is a 30–minute activity in which teams of children, ages 10 to13, investigate the composition of unseen materials using a variety of tools. This open-ended engagement activity mimics how scientists discover clues about the interiors of planets with cameras and other instruments onboard spacecraft.

What's the Point?

  • The interior of a planet cannot be studied directly; scientists must infer the composition and structure from their observations.
  • Different instruments provide different forms of indirect evidence.
  • Scientists use their observations (evidence) to build on what they already know about the universe.
  • Scientific explanations are built on existing evidence and models. New technologies help scientists find new evidence and construct new models. Science advances when these are incorporated into our knowledge of the universe.
  • Models offer a useful way to explore properties of the natural world.


For each group of 20 to 30 children:

  • 5–7 extra-large dark blue balloons filled with air and other assorted materials (below)
  • 2 compasses or magnets
  • Paperclips
  • 1-3 strong magnets, such as cow magnets (available from pet/farm supply stores or science education product retailers)
  • Scraps of paper
  • 10-20 beads
  • 5-10 marbles
  • Optional: Whipped cream from a bottle with a nozzle
  • Optional: Water
  • 2 small scales (such as postage scales)
  • 2 liquid crystal temperature strips (available in most pet stores or stores that sell aquarium fish)
  • 2 magnifying glasses
  • Optional: 2 laser pointers
  • Optional: 2 ear thermometers

For each child:

For the facilitator:


  • Review the background information.
  • Prepare the balloons: After stretching out the balloon, place a magnet, one or more paperclips, several beads, or several marbles in it and inflate it. Repeat for each balloon. If possible, add some water to several of the balloons and then finish inflating them before tying the ends. Tie a secure knot in the end of each balloon.
  • Set out the remainder of the materials on a variety of tables for the children to use.


1. Ask the children how scientists study planets.

  • Are there different tools we can use to study planets? We can use telescopes, and can send robotic spacecraft to the planets. There are different instruments on spacecraft and on telescopes, like cameras and sophisticated detectors, that can be used to study planets.
  • How can we study what's inside a planet? No instruments can "see" inside a planet. We need to use indirect methods to study planetary interiors.

Facilitator's Note: This activity serves as an open-ended engagement activity on how we study the planets. Scientists are able to directly observe some of a planet's characteristics, such as location in the solar system, size, mass, density, gravity, external composition, and more. Mathematicians were able to calculate the planets' orbits based on observations of their movements across the night sky. Telescopes and tools that measure invisible wavelengths of light, called spectrometers, allowed scientists a closer look at the planets' external compositions.

Scientists study the interiors through models they create, which are based on a planet's observable characteristics. Earth's interior is studied in part through seismic data. The giant planets and Earth all have magnetic fields, which are detectable by the radio signals they emit. Magnetic fields are generated deep within planets, so they provide clues to the internal structure and composition. Orbiting spacecraft experience slight variations in their trajectories that help scientists understand a planet's gravity well. By measuring the gravitational pull, scientists can tell more about how a planet's heavy material is distributed in its interior. That information will help them make educated inferences about a planet's composition.

2. Share that the Juno mission launched in 2011 to study Jupiter.

  • One of its goals is to study Jupiter's structure using different kinds of sophisticated instruments. Juno will measure the atmosphere's temperature and amounts of water and ammonia at different depths. This information will help scientists understand the winds deep in Jupiter's atmosphere and piece together Jupiter's internal structure. JunoCam will take pictures of the planet, which scientists and studentswill use to study the poles. Juno will study Jupiter's magnetic field. It has cameras and sensors that will study Jupiter in visible light, in ultraviolet, infrared, and radio. It will keep track of how its orbit is slightly changed by the amount of pull from Jupiter; this will provide clues about Jupiter's gravity field. While some of these instruments will provide clues about the inside of Jupiter, none of them will be able to see inside the planet.

3. Tell the children that they are going to explore how we study planets, using balloons as models.

  • What's a model?
  • How does a planet compare with a balloon? We can only see the surfaces or outer layers of planets, just like we can only see the outside of a balloon.
  • What are some ways we can determine what is inside of these balloons? We can feel the balloons and shake them. We can use tools like thermometers, scales, magnets, and compasses to learn more about what's inside the balloon.

4. Invite the children to divide into groups of four and use their senses and the tools in the room to investigate their balloons. Each child or group should write down their observations in their journals. They must be careful not to pop the balloons, but they are allowed to use their senses and other tools to study their "planets." Have each team record a hypothesis about what is inside their balloon in their journals.

5. One at a time, invite each group to share their observations with the others. Ask the groups to share their hypothesis on what is inside of their balloons.

  • What materials do they think are inside their balloons? Are they hard (solid), sloshy (liquid), or feel like a normal balloon (filled with gas)?


Ask the children to compare their balloons to planets.

  • How are the planets like the balloons? We can't see inside a planet or inside a dark balloon. We inferred what was inside.
  • What tools did you use to tell what was inside your balloon? Children might have used the scale to weigh the balloon, compared its weight with familiar objects, and listened to the noises when they shook it, among other things.
  • Can scientists do all of these things to a distant planet? Can they shake it, pick it up, or weigh it? No.
  • How might a scientist study a planet? What kind of tools should a spacecraft have to study a planet? They can see if the planet has a magnetic field with something like a compass or magnet. They can measure its mass by seeing how much it pulls on an object like a spacecraft. The strength of a planet's gravitational pull for its size can help scientists understand whether gases, liquids, or solids make up the planet's insides. They can examine the outside to study its composition.

Reiterate that Juno will investigate Jupiter — like the children did with their balloons — using a variety of sophisticated instruments.

Facilitator's Note: Juno will use sophisticated instruments, such as a microwave radiometer and magnetometer. For more information about the instruments onboard the Juno spacecraft, visit http://www.nasa.gov/mission_pages/juno/spacecraft/.

Invite the children to pop their balloons to test their hypotheses (outside if there is water or whipped cream in any balloon).

Share with the children that scientists can never see exactly what is a planet or how its inside materials are arranged. Scientists cannot "pop" the planet to see if they are right! Their interpretation is based on the evidence they gathered. Their interpretation may be altered in the future as more evidence is collected, or new instruments are created.

If possible, build on the children's knowledge by offering them a future Jupiter's Family Secrets activity. Ten-year-old children may wrap-up their investigations of Jupiter by attending the concluding activity, My Trip to Jupiter, where they create scrapbooks to document their own journeys into Jupiter's deepest mysteries! Invite children ages 11 to 13 to return for the next program and use some of these tools to investigate Neato-Magneto Planets!

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