Education and
Public Engagement
at the Lunar and Planetary Institute
Explore! Jupiter's Family Secrets

Heavyweight Champion: Jupiter

Adapted from Activities 1, 2, 3, and 4, How Much Would You Weigh on Distant Planets? NASA/MSU-Bozeman CERES Project.


Heavyweight Champion: Jupiter! is a 30-minute activity in which children confront their perceptions of gravity in the solar system. The children weigh themselves on scales modified to represent their weights on other worlds to explore the concept of gravity and its relationship to weight. They consider how their weights would be the highest of all the planets while standing on Jupiter, but their mass remains the same no matter where in the solar system they are! They compare the features of different planets to determine which characteristics cause a planet to have more or less gravity.

This activity should be conducted before The Pull of the Planets in order for the children to better understand gravity before they model it. These concepts involve more advanced science than previous activities in Jupiter's Family Secrets, and they explore more deeply the science of the Juno mission and the rich information it will return to us. Facilitators who choose to undertake this activity should have a firm grasp of the scientific basis so that misconceptions are not introduced to the children.

This series is appropriate for children ages 10 to 13.

What's the Point?


For each group of 10 to 20:

For each child:

For the facilitator:


Caution: Offer a Saturn scale ONLY to advanced audiences who are prepared to tackle the high–level concepts broached by this "trick" planet.


1. Ask the children to consider what it would be like to explore other worlds in our solar system.

Optional: Invite the children to jump and test this principle for themselves.

2. Play one or more movies of an astronaut walking on the Moon and assess their opinions.

Invite the children to write their hypotheses in their journals.

Facilitator's Note: There are many different misconceptions about gravity; children may think that it is related to an object's motion, proximity to Earth or the Sun, temperature, magnetic field, atmosphere, or other unrelated concepts. Guide conversations cautiously and listen carefully to what the children say to avoid supporting their misconceptions.

3. Discuss the concepts of weight and gravity.

4. Invite the children to test how much they would weigh on other planets! Ask them to weigh themselves on the scales you modified to see what effect each planet's gravity would have on their weights. In their journals, invite them to record their measurements for each scale. In addition, ask them to note the characteristics for each of those planets.

Facilitator's Note: If you have a Saturn scale, they might notice that they weigh about the same on Saturn and Earth, because Saturn's gravitational pull is about the same as Earth's at its cloudtops (which are far above the planet's bulky — and gravitationally strong — center). Because the force of gravity depends on both mass and distance, planets that are less dense have less gravity at their cloud-tops or surfaces, which are far above the bulk of the mass in their interiors. This is why planets like Saturn appear to have less gravity than Neptune, despite Saturn's greater mass. You may need to remind the children of what they learned in Dunking the Planets in order for them to understand these difficult concepts.

You may also find that different sources report a range of weights/gravity for both Jupiter and Saturn. The point of this activity is simply to gather the sense that the children would weigh different amounts on the different planets, which can be seen regardless of which source is used to define the weight on the planets.

5. Invite the children to consider the planet properties they discovered in Jump Start: Jupiter and recorded in their journals. Alternatively, ask them to research planet properties in books or consider a copy of Family Numbers. Allow them time to consider the hypotheses presented in their journals and form their own conclusions.


Invite the children to share their conclusions about the gravity in the solar system.

If possible, build on the children's knowledge by offering them a future Jupiter's Family Secrets activity. Invite the children to return for the next activity, The Pull of the Planets, where they will discover how gravity governs the motions of the solar system!